“The Emergency Mouse” – A project born out of necessity

Imagine You are working on a project late on a Friday evening and suddenly your mouse stops working… You can not scroll, and the right-side button won’t respond to your clicks… At the same time, you have a project design that has got to get finished… and the shops are all closed already…

These were the circumstances that led to the birth of “The Emergency Mouse” – A project born out of necessity. How did I solve my problem?

Having access to a lot of electronic modules saved the day. As a maker, I always have various modules and gadgets lying around, and on this unfortunate evening, I remember that the RP2040 has USB HID support. Combine that with a simple Analog Joystick module, a rotary encoder and some push buttons, add about 30 minutes worth of browsing the internet, struggling along with a broken mouse – we have to give the old one credit, it had a very long and hard life, and I finally found some example code that did not just jiggle the mouse pointer or do something equally silly…

The only problem with all of that was that the code was for CircuitPython… I generally dislike using Python on a Microcontroller, as I believe it is better suited for the computer, but, I am warming up to the idea… slowly…

The initial fix – a mess of wires on a breadboard

I quickly grabbed a RaspBerry Pi Pico out of a box, plugged it into a breadboard, loaded Circuitpyth and fired up the example code I got on the internet… While promising, It did not exactly do what I wanted… so a few minutes later, after some coding, I had a moving pointer, controlled by the small thumb joystick module, and with the center button as a “right button”…

So far so good… I can work more easily, but still did not have scrolling… so lets hit the datasheets and documentation on the Adafruit Website (not sponsored) and add a rotary encoder… works well, add more buttons, etc etc…

Eventually it was all done, and about 1 hour has passed, but we were left with a huge ugly mess on a breadboard, and a lot of unused GPIO pins.. So this Pico must go… it can be used for something more useful later…

Then my eye fell on a SEEED Studio XIAO RP2040 module, almost begging to be used… This is smaller, more compact… lets try that …

Initial breadboard version, here shown with the SEEED Studio XIAO RP2040

What functions did this “mouse” have

After changing to the XIAO RP2040, things went very quick…

I added two buttons for scrolling up and down, simulating a mouse wheel,
but kept the encoder… which, while VERY awkward to use at this stage, definitely had potential in the long run…

I also added another button to take over the function of a right button, while the center button on the joystick became left…

Disaster averted, with only about 2 hours wasted, I returned to my project and managed to get it finished using the “improvised-mouse-on-the-breadboard” contraption…

That night, while lying in bed, trying to get to fall asleep, the possibilities of this “contraption-on-the-breadboard” would not let me go… I am fairly old-school, and during the late 80’s and early 90’s owned quite a few “roller-ball” mouse devices… these later became trackballs, and being excessively overpriced, was promptly removed from my environment – the old ones did not last very long, and the new ones were, as I said, overly expensive…

I did however never forget the ease of use that first “rollerball mouse” gave me all that years ago, using only my thumb to move it around etc etc…

This idea would have to be investigated, and turned into a PCB… with that, I finally drifted off to sleep…

The PCB design

The next morning came, and due to reasons unknown, as well as being lazy, I decided not to leave the house, and go buy a new mouse. lets try online… No, they are crazy – I am not paying that for a mouse!

All the time using the “contraption-on-the-breadboard”. So this thing started growing on me… lets design a PCB

The Initial PCB design

After a few hours spent on deciding on optimal layout, I came up with this…
It was still a bit unrefined, but definitely had potential… It lacked a dedicated center button, and those momentary push-buttons requires a lot of force to use… but as a prototype, why not…

Let’s get this manufactured.

For this build, since I used a SEEED Studio module, I decided to send it to SEEED for manufacturing… no need to get components from various places, as they should have all in stock…

Seeed Studio’s Fusion service seamlessly marries convenience with full-feature capabilities in one simple platform. Whether you are prototyping or looking for a mass production partner or based on open source product customization requirements and other design manufacturing services, Seeed Studio Fusion service is catered to your needs starting with a simple online platform. https://www.seeedstudio.com/fusion.html

The PCB arrives from the factory

During the entire time that it took for the PCB to be manufactured and assembled, I was still using this “homemade mouse” – I started calling it a mouse now… and it was still on the breadboard… I never did bother to buy a new mouse, yet..


The PCB Arrived today, and apart from a few small soldering issues, looked great… I still had to do a bit of assembly on my own, as there was an issue with the components I wanted being out of stock.. I have plenty in stock of my own, so opted to do manual assembly…


The completed PCB now only needed a joystick, and some firmware…


After adding a few button caps, and mounting everything to a piece of acrylic plate, I had a working prototype…

The Firmware

As mentioned above, the device runs on CircuitPyton. As Such, there are quite a lot of “examples” on the internet, showing you how to do many USB HID “mouse” like things, but generally being completely useless…

I have thus spent quite a lot of time up to now, writing and refining my own version of the firmware, that is actually useful and does actually work.

It has the following features:
X-Y axis control of the mouse pointer via a thumb joystick, with a left click function on the center joystick button, as well as a dedicated “left” button.

A dedicated “right” button
A “virtual center” button made up of simultaneously pressing left and right

Up and down scrolling either using the rotary encoder as a “mouse wheel” or via dedicated up and down pushbuttons.

A dedicated Reset button – this is necessary, as I can not seem to get the device to initialise correctly at computer bootup.

Various software functions, like changing the pointer acceleration by pressing the center button on the rotary encoder

and most importantly, hiding the Circuitpyton drive, only showing it when I actually need access to the code in this device…

Various statuses are indicated using the NeoPixel on the XIAO, making it easy to see in what state the device is operating.

As such, I shall NOT be releasing the firmware at this moment, as it is still far from being perfect. It works, but it can be way better…

Summary and next steps

Since its “birth” late on a Friday night, about 3 weeks ago, I have been using this device, in its various forms as my primary pointer device. It is growing on me more every day, and it is quite comfortable to use – If we ignore the fact that it is not in a suitable enclosure and that I am still making small changes to the firmware from time to time.

I am already planning the next revision, in which I shall replace the momentary push-buttons with proper microswitches, as well as try my hand at designing a proper enclosure.

If you are a 3D printing expert and want to collaborate with me on this, let’s talk…

Multi-Purpose IO Card

When we are working on a prototype, we always need access to pushbuttons, encoders and even displays to test our ideas in the real world. This Multi-Purpose IO Card was designed to help me do just that…

What is on the PCB?

This PCB was designed with my particular work style in mind. I use a lot of I2C devices, IO Expanders, Displays and sensors. It would thus make sense to have I2C on the PCB, to control an OLED display, as well as a PCF8574 IO expander, that is used to drive a 4×4 Matrix Keypad. Two Rotary encoders, as well as another 4 standard push buttons completes the PCB…

The features, summarised is as follows:

1x Matrix Keypad (4×4) Controlled via an PCF8574 IO expander with selectable addressing.
1x SSD1306 OLED I2C Display
4x Momentary pushbuttons, configured to be used with internal pullups – i.e pushing the button pulls the GPIO LOW
2x Rotary Encoders, with integrated Pushbutton, also configured as Active LOW

The board has all of the connectors and jumpers on the back, making it possible to mount it to an enclosure as a control panel.

I have also provided an additional I2C header to make it possible to add additional devices to the I2C bus easily

The PCB in Detail

PCB Top

Starting from left to right, we have two push-buttons, an OLED display, with two rotary encoders below the display, and another two momentary push buttons. On the Right, we have a 4×4 matrix keypad, and various pin headers for connection to a microcontroller of your choice.

On the back, we have the PCF8574 IO expander for the Matric keypad, addressing Jumpers for the IO expander, as well as the two pin headers for connections to and from a microcontroller…

The Pinouts of these are as follows:
Horizontal 15 pin 2.54mm connector
SDA I2C Data
SCA I2C Clock

GND

SW4 Momentary Push Button 4
SW3 Momentary Push Button 3
SW2 Momentary Push Button 2
SW1 Momentary Push Button 1

RE2-D Rotary Encoder 2 Push Button
RE2-B Rotary Encoder 2 Pin B
RE2-A Rotary Encoder 2 Pin A

RE1-D Rotary Encoder 1 Push Button
RE1-B Rotary Encoder 1 Pin B
RE1-A Rotary Encoder 1 Pin A

GND
VCC 3.3v to 5v DC

The Expansion header extends the I2C Bus, as well as proved access to the interrupt pin on the PCF8574. VCC and GND are also provided.

The Schematic


Manufacturing the PCB

I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly and Testing

The assembly of this PCB was relatively easy, as it contains only a single SMD component. I do however have to alert you to a certain caveat…

On the PCB, the I2C OLED display pinout is, from left to right,

VCC GND SDC SDA

I have however come across similar displays that swap the GND and VCC pins… and some that even have SCL and SDA swapped…

It is thus quite important that you check your display BEFORE soldering it to this PCB…

Addressing the PCF8574 is also quite easy, with the jumper towards the top is a high, and towards the bottom is a low… They are marked A2 A1 A0 and thus, counting in binary, all low will be 0x20h and all high will be ox27h

Also, note that there are NO I2C Pullup resistors on the board. My microcontroller PCB’s usually have these already, and most I2C Sensors, including the OLED Display that we use, already include as well…
You should thus check what you have on your own hardware, as it is quite impossible to cater for every situation… In a future version, I may add selectable pullup resistors onto this board as well…

Coding and Firmware

The possible uses of this board is quite broad, and the code possibilities are thus also quite extensive. Since I mainly use ESPHome or the Arduino IDE with most of my projects, I wont be including any specialised code here. I think it is enough to say that almost all of the available PCF8574 Matrix Keypad libraries available for the Arduino IDE will fork with this board…

The pinouts are important, and thus :

Row 0 – P0
Row 1 – P1
Row 2 – P2
Row 4 – P3

Col 0 – P7
Col 1 – P6
Col 2 – P5
Col 3 – P4

As far as ESPHome goes, you will need to
1) Add an I2c bus for your device
2)Add a PCF8574 component
3)Add a Matrix Keypad component, and refer the rows and columns to the pins on the PCF8574 – See below for an example of how I have done that in a previous project.

#I2C bus

i2c:

sda: 4

scl: 5

scan: true

id: I2C_Bus

#
# In my case, SDA is on GPIO4 and SCL is on GPIO5
# This is similar to the standard configuration on a NodeMCU v2 Dev board
#

#
# The next step is to configure the actual IO Expander, which in my case is located 
# at address 0x27
#

#PCF8574

pcf8574:

- id: 'pcf8574_hub'

address: 0x27

pcf8575: false


#
# Now we can add the actual keypad interface to the YAML file
# Take note of the difference from the ESP32 file above.
#
#

#KEYPAD

matrix_keypad:

id: mykeypad

rows:

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 0

# In the ESP32 file, we wHereould specify a pin directly like:
#
# -pin: 17
#
# That approach will not work for us.
# The reason for that is that we have to redirect the GPIO to a 
# physical pin on the PCF8574 IO expander.
#
# That is done with the following syntax
#
# - pin:
#pcf8574: pcf8574_hub -- This is the ID of the PCF8574 device -
#number: 0 -- The actual pin number

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 1

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 2

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 3

columns:

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 7

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 6

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 5

- pin:

pcf8574: pcf8574_hub

# Use pin number 0

number: 4

keys: "123A456B789C*0#D"

has_diodes: false

The Rotary encoders and momentary push-buttons can be handled in the same manner, using standard libraries in the Arduino IDE, or a rotary encoder component in ESPHome…

The OLED display would also be handled as above, with a DISPLAY component in ESPHome…

Summary and next steps

The next steps, for me at least, would be to design and CNC cut a suitable enclosure for the IO panel/Control panel in order to make it easier to use…

The panel was designed to be a tool to aid me while designing, and part of my never-ending battle getting rid of breadboards.

It does its job well, at least so far, and works as I have intended it to.

Simple Smart Light Controller

Adding a bit of automation to a certain area of the house can definitely help with saving energy. With this Simple Smart Light Controller, I aimed to do just that… Let me give you a tiny bit of context… Houses in SE Asia are built to some “questionable” standards and designs, and electrical installations are usually even more suspect… Our house is no exception. Being a rental, I do not want to go and make changes unless things are outright dangerous… Kitchens are usually a mixture of inside/outside areas, and this is where my device fits in…

The light in the outside kitchen consists of a simple bulb that the owner has routed into the house via an electrical flex cord, at least that was standard… But, due to laziness or just whatever, that cord was never terminated into a proper switch… He just added a plug. This is thus my opportunity to make life a bit easier for myself in that area. I could have opted for a standard switch, but then, automating this can take care of another problem… We constantly forget to switch that light off, as the plug is in a “strange place” that is not usually associated with the kitchen lights…


What I have thus come up with is a simple ESP8266-based solution with a single relay ( optically isolated from the board), as well as a few additional GPIO pins, just in case I want to hang some additional sensors onto this in the future.

The device should also be powered directly from the mains, as adding another external AC to DC adapter would definitely NOT do at all!

What is on the PCB


Lets look at the empty PCB, in order to understand better what is where on the board.

Starting on the Left Side, at the bottom corner, we have our mains voltage input, 220V or 110V, depending on where you live. That goes directly into U1, which is a AC-to-DC converter, providing 3.3v at 1A to the board. Note that I did not place a fuse directly on the board. I prefer to have an inline fuse on the line, which is also accessible from the enclosure.

A series of cutouts on the PCB provides additional mains isolation and also prevents mains voltage tracking towards other tracks in the event of a fault.
The Mains area also does not have a copper pour.

In the top left corner, towards the center, is a WAKE jumper. This is connected to GPIO16 and can be used to wake the ESP8266 from “deep sleep” if configured in the firmware.

Relay K1, and its screw terminal connector is in the bottom center of the board, with the relay contacts clearly labelled.

On the right of the PCB, we have the programming header, complete with Auto Flash and Reset circuitry, as well as manual Flash and Reset Buttons below that.

A 3×3 header connector follows, with access to 3.3v, Ground as well as 3 additional GPIO pins for other applications.

Finally, we have the relay control switch, with a few options to connect external switches, either on the 2.54mm header, or via wires soldered to the pads marked SW-A and SW-B


The populated PCB will thus make more sense if we look at the picture above now since we had a detailed look at it above…


The Schematic is made available at the link above.

Configuration and Software

This build was designed with ESPHome in mind, so we will focus on that there.
You can however very easily use standard Arduino/ESP8266 code to control this as well…

The YAML configuration for the device will be as follows: (note that this is quite simplified, as I am still fine-tuning the actual features that I require)

esphome:
  name: smart-switch-01
  friendly_name: SMART-SWITCH-01

esp8266:
  board: nodemcuv2
  restore_from_flash: true

# Enable logging
logger:

# Enable Home Assistant API
api:
  encryption:
    key: "hfYNn8KSbVq26rGkPOJo4yLj/d/WY7Hk0H3TmxlWZAU="

ota:
  password: "85ed2a8afcd61d0f4c65db7b92bdacc5"

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "Smart-Switch-01 Fallback Hotspot"
    password: "XovAx4n1H1qT"

captive_portal:

text_sensor:
  - platform: wifi_info
    ip_address:
      name: IP Address
    ssid:
      name: SSID
    bssid:
      name: BSSID
    mac_address:
      name: Wifi MAC
    scan_results:
      name: WiFi Scan Results


sensor:
  - platform: adc
    pin: VCC
    name: "ESP8266 Chip Voltage"
    id: mcu_voltage
    unit_of_measurement: "V"
    device_class: "voltage"
    accuracy_decimals: 2
    update_interval: 60s
    entity_category: "diagnostic"
    
  - platform: wifi_signal
    name: "WiFi Signal Sensor"
    id: wifi_strength
    device_class: "signal_strength"
    unit_of_measurement: "dBm"
    update_interval: 240s
    entity_category: "diagnostic"

  - platform: copy # Reports the WiFi signal strength in %
    source_id: wifi_strength
    name: "WiFi Signal Strength"
    filters:
      - lambda: return min(max(2 * (x + 100.0), 0.0), 100.0);
    unit_of_measurement: "%"
    entity_category: "diagnostic"


light:
 # - platform: status_led
 #   pin: GPIO13
 #   id: status_indicator
 #   name: "ID Light"
    
  - platform: binary
    name: "Kitchen Outside Light"
    output: relay_01
    id: kitchen_light
    on_turn_on:
    - light.turn_on:
        id: slow_light
        effect: "Slow Pulse"
    

    on_turn_off:
    - light.turn_off: slow_light
    

  - platform: monochromatic
    id: slow_light
    output: light_status
    restore_mode: RESTORE_AND_OFF
    effects:
      - pulse:
          name: "Slow Pulse"
          # transition_length: 1s      # defaults to 1s
          update_interval: 2s

binary_sensor:
  - platform: gpio
    pin:
      number: GPIO5
      mode:
        input: true
        pullup: true
    id: kitchen_light_toggle
    filters:
      - delayed_on: 200ms
      - delayed_off: 200ms
    on_press:
      then:
        - light.toggle: kitchen_light
  - platform: status
    name: "Kitchen Light Controller"
     
switch:
  - platform: restart
    name: "Restart Device"

# Relay output
output:
  - platform: gpio
    id: relay_01
    pin: GPIO4
    inverted: true
  - platform: esp8266_pwm
    id: light_status
    pin: GPIO12
 

Manufacturing the PCB

I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly and Testing

This device does not need a stencil for assembly, but using one will definitely speed up things. I chose to do this build all by hand, from applying solder-paste, up to placing components.

Soldering was done on a hotplate, as usual, to reflow everything at the same time. TH components were then placed and hand-soldered.

Uploading the initial firmware, after adding the device to ESPHome was done with an external USB-to-UART converter. All further firmware changes were made via OTA.

Enclosure and some of the wiring

It is important to mention here that this PCB is powered by mains voltage. I chose to use an inline fuse, BEFORE the connector on the PCB. It is also notable that the relay common is connected to the live wire, BEFORE the fuse, as the lightbulb acts as its own fuse – it blows when a fault occurs.

The Lightbulb neutral will be connected to the circuit breaker, together with the device live and neutral.

This way, the fuse only acts on the actual device, and I can use a lower-rating fuse, since I do not have to accommodate the current from the lightbulb as well…

Summary

The device works as planned, with no problems…
Below is some pictures from it in Home Assistant

An I2C Matrix Keypad

The completed I2C Matrix Keypad

In a previous post this month I introduced my 4×4 matrix keypad. That keypad was designed to be directly interfaced to a microcontroller’s GPIO pins or alternatively to an IO expander chip like the PCF8574. That design, while working very well had the problem of requiring 8 GPIO pins to function correctly.

GPIO pins on a microcontroller can be considered very precious resources, and it should then be logical to assume that we should find a way to use these GPIO pins in a more conservative way, to allow us to interface more peripherals.

I solved this problem by integrating the keypad with an IO Expander on the same PCB. That will allow us to get away with using only 2 GPIO pins, and also open up the option of adding more keypads to the I2C bus, in the event that we need that many keys for a particular project.

The Schematic

I2C 4×4 Matrix Keypad Schematic

Looking closely at the schematic, we can see that it is exactly the same basic keypad circuit that I used in the initial design. The only difference is that in this design, I have integrated a PCF8574 directly onto the PCB.

Some additional features include selectable I2C Pullup resistors ( usually my microcontroller development boards already include those) that can be activated with a jumper when needed. There are also a set of address selection jumpers, making it possible to stack keypads together into a bigger keyboard if you require something like that. Note that, in this version of the hardware, I did not include headers for stacking.

The keypad can be powered by a DC power source of 3.3v to 5v.

The PCB

I2C Keypad PCB
3D Render of the I2C Keypad

The PCB is a double-layer board of 68.8mm x 50.8mm. Male header pins provide access to the connections as well as address and pullup resistor jumpers. In my build, I have mounted these male headers on the back of the PCB. That makes it possible to mount the Keypad in an enclosure without having the jumpers “stick out” and get in the way.

The top layer of the I2C Keypad PCB
Bottom Layer

Manufacturing

I choose PCBWay for my PCB manufacturing.
This month, PCBWay is also celebrating its 9th anniversary, and that means that there are quite a lot of very special offers available.

Why?
What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly

The assembly of this PCB was quite easy and quick. A stencil is not required. All SMD components are 0805 or bigger. It would thus be quite easy to solder them all by hand with a fine-tipped soldering iron.

I have however used soldering paste and hot air to reflow the components, as it is the fastest, in my opinion, and definitely looks neater than hand soldering.

After placing SMD components onto solder paste – ready for reflow soldering
After Reflow soldering with Hot Air

The board is now ready to solder the switches and header pins in place. As already mentioned above, I chose to assemble the headers on the back of the PCB to prevent them from interfering with any enclosure that I may later use with the keypad.

Final Assembly
Note that I assembled the headers onto the back of the PCB.

Testing and Coding

Testing the keypad consisted of a few steps, the first of which was ensuring that there were no short circuits, as well as that all the momentary switches worked.
This was done with a multimeter in continuity as well as diode mode, with probes alternatively on each column and row in turn, while pressing the buttons.

The next stage was testing the I2C IO Expander. This was done with a simple I2C Scanning sketch on an Arduino Uno. It did not do a lot, but, I could see that the PCF8574 is responding to its address and that the pullup resistors work when enabled. This test was repeated with my own ESP8266 and ESP32 boards, this time with pullup resistors disabled, as these boards already have them onboard.

Coding came next, and it was another case of perspectives. It seems like all commercial keypads do not have diodes. This affects the way that they work with a given library. It seems that software developers and hardware developers have different understandings of what a row and a column is.

This meant that, due to the fact that I have diodes on each switch, and the way that the library work – which pins are pulled high and which are set as inputs -, I had to swap around my rows and columns in the software to get everything to work. On a keypad with the diodes replaced with 0-ohm links, that was not needed.

A short test sketch follows below:

Note that with was run on an ESP8266-12E, therefore the Wire.begin() function was changed to Wire.begin(4,5); in order to use GPIO 4 and GPIO 5 for I2C

Another point to note is that the keypad Layout will seem strange. Remember that this is due to the diodes in series on each switch. That forces us to swap around the Rows and the Columns in the software, resulting in a mirrored and rotated left representation of the keypad. It looks funny, but believe me, it actually still works perfectly.

#include <Wire.h>
#include "Keypad.h"
#include <Keypad_I2C.h>

const byte n_rows = 4;
const byte n_cols = 4;

char keys[n_rows][n_cols] = {
    {'1', '4', '7', '*'},
    {'2', '5', '8', '0'},
    {'3', '6', '9', '#'},
    {'A', 'B', 'C', 'D'}};

byte rowPins[n_rows] = {4, 5, 6, 7};
byte colPins[n_cols] = {0, 1, 2, 3};

Keypad_I2C myKeypad = Keypad_I2C(makeKeymap(keys), rowPins, colPins, n_rows, n_cols, 0x20);

String swOnState(KeyState kpadState)
{
    switch (kpadState)
    {
    case IDLE:
        return "IDLE";
        break;
    case PRESSED:
        return "PRESSED";
        break;
    case HOLD:
        return "HOLD";
        break;
    case RELEASED:
        return "RELEASED";
        break;
    } // end switch-case
    return "";
} // end switch on state function

void setup()
{
    // This will be called by App.setup()
    Serial.begin(115200);
    while (!Serial)
    { /*wait*/
    }
    Serial.println("Press any key...");
    Wire.begin(4,5);
    myKeypad.begin(makeKeymap(keys));
}

char myKeyp = NO_KEY;
KeyState myKSp = IDLE;
auto myHold = false;

void loop()
{

    char myKey = myKeypad.getKey();
    KeyState myKS = myKeypad.getState();

    if (myKSp != myKS && myKS != IDLE)
    {
        Serial.print("myKS: ");
        Serial.println(swOnState(myKS));
        myKSp = myKS;
        if (myKey != NULL)
            myKeyp = myKey;
        String r;
        r = myKeyp;
        Serial.println("myKey: " + String(r));
        if (myKS == HOLD)
            myHold = true;
        if (myKS == RELEASED)
        {
            if (myHold)
                r = r + "+";
            Serial.println(r.c_str());
            myHold = false;
        }
        Serial.println(swOnState(myKS));
        myKey == NULL;
        myKS = IDLE;
    }
}

Conclusion

This project once again delivered what I set out to achieve. It has some quirks, but nothing serious. Everything works as expected, both in the Arduino IDE/platform IO realm, as well as in ESPHome. It is worth noting that in ESPHome, we do not need to swap the rows and columns to use the Keypad component. Do remember to leave the has_diodes flag to false though…

ESP32-S DEV Board – Rev 2.0

A few months ago, I started to work on an ESP32-S SOC module in Arduino Uno form factor. This is Revision 2.0 – the ESP32-S Dev Board – Rev 2.0

During the time since I designed, and ultimately had the Rev 1.0 PCB manufactured, It has quickly become one of my go-to development platforms, something that I hoped it would become. It also seemed to be gaining popularity online, with quite a few of them being ordered.

Problems did however arise, as the manufacturer discontinued the SOC module, the AI-Thinker ESP32-S, but, as this was based on the ESP32 WROOM32 from Espressif, which, while still old, was still in production, it was not a serious problem.

Using the Rev 1.0 device was easy enough, but I soon started to experience some irritation, as in my attempts to build a very streamlined device, I left out some add-on components, that now seemed to be a very good idea to have on board…
Let me explain:

In the initial design, I did not include a DC barrel connector, as well as no USB port with a USB-to-serial converter, my argument being that the USB port is usually only used a few times, or at most once, as I usually upload firmware to ESP32’s OTA. Power ( on the bench that is, is usually supplied via a pair of wires, so no dedicated connector seemed to be necessary.

As I proceeded to design addon shields for the device, it became clear that that power connector, at minimum, as well as the standard 2-transistor reset/flash circuit, would be a very very welcome addition to this PCB.

See the pictures below for a comparison of the two boards…

ESP32-S Dev Board Rev 1.0
ESP32-S Dev Board Rev 1.0
ESP32-S Dev board Rev 2.0
ESP32-S Dev Board Rev 2.0

I have also decided to use male header pins on this build, as I sort of like to use them more than the female ones ( which seem to develop connectivity issues after a while – this could be due to the quality of the connector strips that I bought)

What changed, and how?

I made quite a few changes, most of them quite subtle.
The most obvious would be the addition of a DC Barrel connector, to allow the device to be powered easier when used as a permanent project. In addition to this, a 6-pin programming header was added, in order to make flashing the device with an external USB-to-serial adapter easier than usual. ( This means that the standard 2-transistor reset/flash circuit was also added). That meant a slight increase in the component count. Additional decoupling capacitors were also added to add voltage stability to the ESP32-S. The routing of the entire board was also changed, with more attention being paid to the heat dissipation of the ESP32-S module, which tended to get a bit hot.

Power is provided by a 3.3v LDO regulator, the same as in the Rev 1.0 hardware.
I do plan to change this to a small buck converter in the near future, as the 800mA provided by the LDO regulator can get a bit limited, especially when using I2S Audio devices, something which I am doing quite a lot over the last few months.

Manufacturing

I choose PCBWay for my PCB manufacturing.
This month, PCBWay is also celebrating its 9th anniversary, and that means that there are quite a lot of very special offers available.

Why?
What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly

This PCB will definitely benefit from using a stencil, but it is not strictly necessary. I did however get one, as I prefer the uniform solder-paste application and speed that they give me.

Stencil for SMD assembly

Component placing took only about 10 minutes in total, including the time needed to place and use the stencil, apply solder paste, select components and place them in their correct positions.

After Solder paste application – Before reflow soldering

The board was then reflow soldered on a hotplate at 223 degrees Centigrade.

After Reflow soldering

The board was inspected for solder bridges and bad joints, and I then proceeded with through-hole component assembly, which took about another 10 minutes.

ESP32-S Dev board Rev 2.0
The completed PCB

Conclusion

This was definitely a very worthwhile revision on a very useful piece of equipment. The addition of the programming header, in particular, already saves quite a bit of time, and the DC Barrel connector opens up new possibilities for the use of the device outside of the “bench” environment.

A quick P-MOS MOSFET Driver Board

Introduction

A driver is needed to switch a P-Channel MOSFET because the gate of a P-Channel MOSFET needs to be driven to a voltage that is more negative than the source in order to turn it on. This can be difficult to do with low-voltage logic, such as 5V or 3.3V. A driver can provide the necessary voltage and current to turn on the P-Channel MOSFET, even when the logic voltage is low.

Here are some of the benefits of using a driver to switch a P-Channel MOSFET:

  • Increased switching speed: A driver can provide the necessary current to charge and discharge the gate capacitance of the P-Channel MOSFET quickly, which results in faster switching speeds.
  • Reduced power consumption: A driver can help to reduce power consumption by providing the necessary current in a short pulse, rather than a continuous stream of current.
  • Improved noise immunity: A driver can help to improve noise immunity by providing a clean and isolated signal to the gate of the P-Channel MOSFET.

If you are using a P-Channel MOSFET in your circuit, it is a good idea to use a driver to switch it. This will help to ensure that the MOSFET is switched quickly and efficiently and that it is protected from noise.

Here are some of the different types of drivers that can be used to switch P-Channel MOSFETs:

  • Logic level drivers: These drivers are designed to work with low-voltage logic, such as 5V or 3.3V. They typically have a high output voltage, which can be used to drive the gate of a P-Channel MOSFET.
  • High-side drivers: These drivers are designed to provide a high voltage to the gate of a P-Channel MOSFET. They are often used in circuits where the P-Channel MOSFET is used to switch a high-voltage rail.
  • Isolated drivers: These drivers provide an isolated signal to the gate of the P-Channel MOSFET. This is useful in circuits where it is important to prevent noise from entering the circuit.

Why did I decide to design this prototype?

The Story behind the prototype

This driver PCB is part of a solution for a project involving a set of 6v LED lights.
Each of the LED lights requires +/- 300mA @ 6v to operate efficiently.
I want to control these from a Microcontroller, either an ESP32 or even the XIAO RP2040 or similar. The current sink capability of an individual GPIO pin on these microcontrollers is limited, in the case of the RP2040 it is limited to 3mA per pin.

This prototype is an attempt to test out some basic driver ideas that might perform correctly for my particular needs, being

  • To stay within the limitations of the particular microcontroller GPIO current specifications
  • To be able to use any of the particular microcontrollers, without having to design a specific solution tailored to a specific device

The Schematic

I decided to keep things extremely simple to start with, using a very simple circuit consisting of only 4 components per channel. These are :
– an S9013 NPN BJT Transistor, capable of switching up to 500mA of current
– a SI2301 P-Channel Logic Level MOSFET, capable of switching up to 2.3A
– 10k pullup-resitor
– 1k resistor on the base of the BJT


The theory of operation is as follows:
The pullup resistor, R8, keeps the gate of the MOSFET (Q4) positive, thus ensuring that Q4 stays turned off when T4 is turned off. A HIGH signal at B4 will turn on T4, which will in turn pull the gate of Q4 to ground, turning Q4 on in the process.
That will in turn turn on the load ( connected at 4+ and 4- ).

It is important to note here that the value of R8, 10K at the moment, is not finalised, and may change to increase the performance of the circuit.

The PCB

The board was made to fit on a standard breadboard or be used as a standalone module, depending on the position of the male header pins.


Manufacturing


I choose PCBWay for my PCB manufacturing.
This month, PCBWay is also celebrating its 9th anniversary, and that means that there are quite a lot of very special offers available.


Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly

The assembly of the PCB does not require any special tools, and can be done completely by hand if you choose. A very fine-tipped soldering iron should be perfect.

I chose to go the hot-air and solder-paste route, as it is faster, and looks neater in the end. The use of a stencil was not required.

The total assembly took about 5 minutes in total.

Testing

Testing the completed PCB module was performed with one of the LED light modules connected to each MOSFET Channel in turn, and then applying a voltage signal, or ground, to the control pin ( marked A to D on the picture above)

That was followed by connecting an Oscilloscope and Signal Generator to the control pins, as well as the outputs, and observing the waveforms during operation. A square wave output from the signal generator provided the switching signal.

Conclusion

The module works as expected, but the pullup resistor value needs to be fine-tuned to provide a better switching response on the MOSFET at high frequency.
I am however happy with the initial performance, and can now move on to improving the circuit to perform to my specifications.


A Reliable Matrix Keypad

What is a matrix keypad?

A matrix keypad is a type of keypad that uses a matrix of wires to connect the keys to the microcontroller. This allows for a smaller and more compact keypad than a traditional keypad, which uses a single row and column of wires for each key. Matrix keypads are also more reliable than conventional keypads, as they are less susceptible to damage from dirt and moisture.

How does a matrix keypad work?

A matrix keypad is made up of a number of rows and columns of keys. Each key is connected to two wires, one for the row and one for the column. When a key is pressed, it completes a circuit between the row and column wires. The microcontroller can then determine which key is pressed by checking which row and column wires are connected.

Why use a matrix keypad?

There are a number of reasons why you might want to use a matrix keypad in your project. Here are a few of the most common reasons:

  • Smaller size and footprint.
  • Reliability.
  • Cost savings.

What makes my design different from most others out there?

While the matrix keypad in its simplest form is constructed from only wires and switches, that simple approach can sometimes have some unwanted effects, especially when pressing multiple keys at the same time – a phenomenon called ghosting – where you get phantom keypresses. This is easily eliminated by adding a diode in series with each switch, usually on the row connection.

That single component fixes ghosting reliably but does not come without its own problems, the most important of these being that a keypad with diodes becomes “polarised” – current can only flow in a single direction through a switch. This can cause problems with some third-party libraries, as the designer of the keypad and the designer of the library very often has quite different ideas of what a row and a column mean in a keypad.

This is important, – here we go down the rabbit hole; in my understanding of the keypad scanning routine, a column runs from top to bottom, and a row from left to right. Keeping this in mind, the microcontroller will alternatively set each column HIGH, and configure each row as an input. When a key is pressed, current will flow from the specific column GPIO, through the switch, and into the Row GPIO, sending the input pin HIGH…

It is also possible to configure the columns as inputs, with internal pullups enabled, and have each Row pin as an output, configured to sink ( pull current to ground). This will cause the specific column to go low – thus identifying the pressed key…

These different ways of handling the problem of reading a key, and believe me, there are actually more variations, create a few unique problems. We may have to swap rows and columns as far as pin connections and firmware are concerned, as well as define a custom “keymap” to assign values to each key.

The Schematic

As we can see above, the schematic is very basic. 16 switches, 16 diodes and a single 8-way header pin. Pin 1 to 4 on the header is connected to Columns 1 to 4, and Pin 5 to 8 is connected to Rows 1 to 4.

The diodes prevent “ghosting currents from flowing into other keys in a row when multiple keys are pressed together. They also seem to help with other stray signals and interference.

The PCB

The PCB is a simple double-layer board. All components are mounted on the top layer.

To limit interference from stray signals, I have routed rows and columns on opposite sides of the PCB where possible.

Manufacturing

I choose PCBWay for my PCB manufacturing.
This month, PCBWay is also celebrating its 9th anniversary, and that means that there are quite a lot of very special offers available.


Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly

This project does not require a lot of specialised equipment to assemble. The SMD diodes can easily be soldered by hand, the same with the switches and 8-way header. In my case, I chose to solder the header pins on the back of the PCB, that way, I can later use the keypad in a suitable enclosure without having wires in the way.

Testing and Coding

Testing a matric keypad can sometimes be a challenge. In my case, a multimeter with clip leads, set to diode mode, with the leads connected to each column and row in turn, while minding the polarity, and pressing each key in that row in turn, verified continuity.

With that done, it was time to put my trusted Cytron Maker Uno to work, as this Arduino Clone has the added benefit of having LEDs on each of the GPIO lines, thus making it very easy to see what is happening.

I made use of a Keypad library in the Arduino IDE, mainly to cut down on the amount of coding, but also because it is easier to use a working piece of code, and then adapt that to my keypad.

Detailed Code examples for ESPHome are available on Patreon

/* @file CustomKeypad.pde
|| @version 1.0
|| @author Alexander Brevig
|| @contact alexanderbrevig@gmail.com
||
|| @description
|| | Demonstrates changing the keypad size and key values.
|| #

Edited by MakerIoT2020, with minor changes to make it function correctly with my custom keypad.
I have also added a simple LED blinking routine to show that the Arduino is “alive” and that the Keypad code seems to be NON-blocking – which is quite important to me.

*/
#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
//define the symbols on the buttons of the keypads
char hexaKeys[ROWS][COLS] = {
{‘1′,’4′,’7′,’*’},
{‘2′,’5′,’8′,’0’},
{‘3′,’6′,’9′,’#’},
{‘A’,’B’,’C’,’D’}
};
byte rowPins[ROWS] = {2,3,4,5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {6,7,8,9}; //connect to the column pinouts of the keypad
/*
* Due to libraries being written by different people, and our definitions about
* what a row and a column are, is different, note that the rows in the code
* is actually the columns on my PCB. This becomes true, due to the fact that my
* PCB has Diodes on each switch, and that thus makes current flow in only one
* direction///
*
* it also has the “side effect” that keys are layout in a strange “mirrored” and
* rotated way in the firmware.
* it does however NOT affect the correct operation of the Keypad Module at all
*
*/

const int LEDPin = LED_BUILTIN;
int ledState = LOW;
unsigned long prevmillis = 0;
const long interval = 1000;

//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);

void setup(){
Serial.begin(115200);
pinMode(LEDPin,OUTPUT);
}

void loop(){
unsigned long currentMillis = millis();
if (currentMillis – prevmillis >= interval) {
prevmillis = currentMillis;
if (ledState == LOW) {
ledState = HIGH;
} else {
ledState = LOW;
}
digitalWrite(LEDPin,ledState);
}
char customKey = customKeypad.getKey();

if (customKey){
Serial.println(customKey);
}
}

This code works very well and allowed me to verify the correct operation of the keypad.

In conclusion

Making my own Keypad Module is a project that is long overdue. I have purchased a few online over the years, and as they were mostly of the membrane type, they did not last very long – it must be something to do with the ultra-cheap flexible PCB ribbon connector, since a quality membrane keypad can be quite expensive, and usually lasts quite a long time.

Having my own module available to experiment with will allow me to do some long-delayed improvements to many of my IoT modules. That code, mostly YAML for ESPHome, will be made available on Patreon.

My Own DC-DC Buck Converter

Dc-to-DC Back converters have a lot of advantages over traditional linear voltage regulator solutions. Most of these advantages are related to the smaller size of these circuits, in comparison to their linear counterparts, as well as their higher efficiency and lower power consumption to name a few.

I am by no means a power supply guy, and as such, I usually buy my power supply modules. The same also applies to boost and buck converters. I am usually quite comfortable leaving the design of these critical parts to those who actually know what they are doing.

It thus seemed like a reasonable challenge to actually try and design and build one by myself, and that will be the story behind this post.

Finding a suitable driver IC

This journey started at a very strange place. When I decided to go ahead and build this Buck converter module, I had no specific driver IC in mind. I was thus browsing through the long list of dc-to-dc- buck converters on my component suppliers’ website, randomly pulling up a datasheet to take a closer look, mainly looking for something with as few external components as possible, while also having a decent current supply capability, as well as being able to operate on an input supply of 4v to about 24v, which is well within my usual range…

I eventually settled on the MPS MP9943. Definitely not the cheapest but still affordable, and in a QFN8 package, so that I am still able to actually solder it to a PCB!

-Wide 4V to 36V Continuous Operating Input
Range
-85mΩ/55mΩ Low RDS(ON) Internal Power
MOSFETs
-High-Efficiency Synchronous Mode Operation
-410kHz Switching Frequency
-Synchronizes from 200kHz to 2.2MHz
-External Clock
-High Duty Cycle for Automotive Cold-crank
-Internal Power-Save Mode
-Internal Soft-Start
-Power Good Indicator
-Over Current Protection and Hiccup
-Thermal Shutdown
-Output Adjustable from 0.8V
-Available in an QFN-8 (3mmx3mm)
package

and with a peak current supply of up to 3A – Not too bad at all.

The actual design

As mentioned already, I am not ( or at least I don’t see myself) a power supply design expert. I believe I am perfectly capable with the linear stuff, by switchmode was never my strong point 🙂 This prototype will just be based on the recommended design in the datasheet, at least for the first version, and then, later versions may feature some customisation as actually needed.

From the picture above, we can see that there are indeed not a lot of external components required. And in my humble opinion, the efficiency vs load also seems to be quite reasonable.

I thus went ahead and started reading this datasheet in detail. I found two typical-use circuits with recommended component values, from which I build my prototype.

I chose to combine these two circuits to give me a variable output module, that will be selectable between 5v and 3v.

I also chose an inductor with a 6A maximum current rating, as the datasheet states that we should choose one with at least a 25% higher current rating than our peak requirement. My logic here was that 100% would be a good number, as the inductor would in theory never saturate?? as well as produce less heat etc ?? Please comment on this, as I may be barking up the wrong tree here 🙂


The schematic above is what I came up with. A jumper will allow the selection of the output voltage, as this is determined by the value of the resistor at R8, in my case 13K or 7.68k… I also assume that that resistor can later be replaced by a 20k trimpot or similar to give a truly variable output.

PCB Layout

The PCB layout was an attempt to follow the datasheet recommendations as closely as possible, while still having my own design. I am also aware that I may have wasted quite a bit of space, but for now, my focus is on getting a working design. I can always try to squeeze it into a smaller space later.

Manufacturing

I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly

After receiving the PCBs back from the factory, and receiving the components from the supplier, I started on the assembly. While uneventful, It was worth mentioning that this project does require a stencil. The DFN-8 package is quite small (only 3mmx3mm), with eight leads, so that makes for some tiny spacing between them. As it is also a leadless package, I did not want to chance to have too much solder paste in there.

As we can clearly see in the picture above, the pads are super tiny. The other components are 0805 ( for reference).

My standard way for assembling DFN packages is to actually level the part of the PCB while reflowing the PCB with a hotplate. Then, when the solder has all melted and is in a liquid state, I carefully place the part with tweezers and remove the PCB from the hotplate.

Alternatively, I remove the PCB from the hotplate first, leaving it to cool down a bit, and then, using a hot air gun with a small nozzle, reflowing only the area where the part needs to be placed, and carefully placing it onto the melted solder.

Both of these methods seem to be working quite well, for me at least, but the hot air method does however have the risk of a bit of solder splatter, which may form unwanted bridges… The part also gets heated a bit, as it has to be held in place for a few seconds to prevent it from being blown around by the hot air.

Testing


I am quite happy to report that the module works as expected, with a steady output of 3.31v and 5.08v respectively at no load.

Under load, I tested with a 1A and 2A load respectively, both voltages are also stable. Ripple, as measured by myself, and using a “not too good” digital oscilloscope, seems to be about 110mv peak-to-peak.

Using better probes, and a better scope, I may be able to get a better and more accurate reading.

Conclusion

This was quite an exciting project, with setting myself a challenge, and actually achieving what I set out to do. While I am sure that the module in its current state may actually not quite be perfect, and that it surely has a lot of room for improvement, I am satisfied with its performance, and just plainly, the fact that it actually works!

Breadboard Power Rail Bridge

This is a sort of tongue-in-the-cheek project, that started with good intentions, and ended up wholly over-engineered and sort of “broken” due to adding “added features” like LEDs and an additional power header.

What was the initial intention?

[This is what I actually wanted to achieve]


My breadboards all have interrupted power rails, and it is thus always necessary to bridge them with jumper wires to have a continuous rail. This is needed because I very often have more than one project on a single breadboard, and do not want to have to use separate power modules for each. I also tend to test out some part of a circuit on a separate part of the breadboard, before incorporating it into the main circuit.

[ I completely overdesigned this, ending up with something completely different from what I wanted]


Wire jumpers are definitely the easier and fastest, but having been struck by a “what if I do this instead” moment, this tiny PCB was designed and subsequently sent to manufacturing…

So does it work?

Yes, it works, for its intended purpose of bridging the power rails, but that is where the wheels come off. Let me explain, trust me, it will be fun, and we can all laugh at it in the end…

Breadboard power rails are usually marked Red for positive, and Blue or Black for negative… Most people on this planet are also right-handed, and would thus place a power module on the right-hand side of a breadboard ( although some won’t..) Being left-handed myself, and still trying to please right-handed people, my power module will be “upside down” on the left-hand side of a breadboard… which is fine with me, as I remember to swap the colours of the rails in my mind, making red negative and blue positive… not a big issue is you always do it that way…

So what went wrong…

While designing this, I initially planned on a simple PCB bridge, with a jumper on the positive line, acting as a switch, and a continuous ground that is always connected.. all fine, problem number 1 being that I looked at the colours of the power rails while designing it, measuring the gaps etc to get the spacing just right…

Problem number 2 is that the top and bottom rails are in the same configuration, Red at the top, blue at the bottom… and thus plugging in a bridge into either should be ok… and it really should have been, if I did not decide to add a status LED on each side of the bridge, and an additional power header… because turns out that I forgot that the bridge at the top will in effect be “mirrored” when plugged in ( and thus having components that are reversed polarity) – mirrored, due to the fact that you now have to plug the top rail bridge upside down into the breadboard, because it will otherwise interfere with the prototyping space

[This was the direct effect of my lack of attention to detail – and yes, it works perfectly in this configuration – if we ignore the wasted space on the top half of the board]

[This is the practical reality – one bridge must be installed ‘upside-down’]

Lesson learned; I can be quite scatterbrained at times, especially when juggling a few projects and customers at the same time ( I am only human anyway ). Thus this project, although it looks nice, and can be useful, needs to go back to the drawing board for a complete redesign, without all those “added features”

The Schematic


The schematic is straightforward, with no surprises. Two LEDs ( polarity sensitive ) and then those headers and jumpers, which also need up being polarity sensitive – in a manner of speaking

Quite different from what I originally wanted to do

Manufacturing

I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Conclusion

This project served many purposes beyond the actual use of the PCB that was designed. In a way, I am quite happy that I screwed up so badly on this one – here is the reason why:

Because I do quite a lot of PCB design each month, for customers or personal projects, I often tend to get a bit over-confident, and also rush things through,
while believing that I will catch every mistake before I send something off to production. Normally, I am quite good at that, and my error rate is actually quite low… But, This month, being quite busier than usual, and having had a fair amount of distractions, served as the perfect lesson to drag me down a notch or two, and remind me that I have to be way more attentive, especially when things are going hectic, and there are a few projects to juggle around at the same time.

The second reason why it is a good thing when the wheels come off like this, once in a while, is that it serves as a perfect example of what your PCB manufacturer’s actual job is. So, this is especially for the new guys that may not know this: Your PCB Manufacturer has only one job – To manufacture your PCB EXACTLY AS YOU DESIGNED IT – Scary, right? Sure, they will let you know if your design falls outside of their tolerances of capabilities. They will let you know if your board fails a flying probe test if you have that kind of arrangement with them… But it is NEVER their job to correct or attempt to change any of your design files.

So, what is the moral of the story, regarding both of the points that I made above?

If you screw up on the design, it is your, and only your fault. Nobody else is to blame, ever. The buck stops with you, the designer.

Breaking out of the Chip Shortage – Attempt #3

The ATMEGA4808 provides a very attractive solution to replace the trusted ATMEGA328 or standard Arduino UNO /NANO.

These chips are slightly more difficult to get hold of than the ATTiny chips, and cost a little bit more ( about the same as what the ATMEGA328 used to cost before the mess with COVID-19 and resulting supply chain shortages + inflated costs), but they offer all of the functions of the ATMEGA328, with a few other enhancements that will definitely be very useful.

The extras include:
– Hardware interrupts on ALL GPIO pins; This is way more than the standard 2 interrupts on the ATMEGA328 ( We are not talking about the Pin Change interrupts, but real hardware interrupts, that can be triggered on RISING, FALLING, CHANGE, HIGH and LOW state of each pin

– Up to eight (8) PWM pins as opposed to the 6 on the Arduino UNO
– Up to eleven Analog inputs
– An Analog Comparator module
– Configurable Custom Logic (CCL)
– EVENT System (EVSYS)
– Peripheral pin swapping

It is also worth mentioning that these chips have accurate internal oscillators, capable of clocking the chip at up to 20MHz, further reducing the number of external components required to get a minimal configuration running…

Order your own version of this development board

The Prototype PCB

While I have had a Nano Every “Clone” lying in a drawer for quite a while now, I did not really pay a lot of attention to it. That was, until I needed an ATMEGA328 for a project, and could not find any for sale, or at least at a price that I was willing to pay for it… That incident was the spark that ignited this entire exercise, to find a suitable replacement…

The Nano Every “Clone” in my possession, used the ATMEGA 4808 chip and turned out to be the Thinary Nano 4808. I had quite a lot of problems with the provided core, as well as getting peripherals like I2c and SPI to work. This led to further investigations, and finally, I decided on building my own and to use the MCUdude/MegaCoreX Arduino Core to program it.

This led to the following prototype:

ATMEGA4808 Development board prototype

I did not bother with too much detail on the silk screen here, as the goal was to get a working board, test it, and then later, design a refined PCB.

What is important to note is that the board runs at 5v, but provides a single 3.3v output as well. Logic levels on the GPIO is also 5v. Use level converters for 3.3v only addons…

The MEGA4808 is programmed via UPDI, so we have a UPDI Header on the right-hand side of the PCB. It is also possible to use the Optiboot Bootloader, to flash the board in true Arduino style through a USB connection to a computer.

A CH340N USB-to-Serial converter chip is used instead of the CH340G that is common on the UNO clones. The CH340N provides only the USB D+ D- signals, as well as Rx, TX and RTS. RTS is being used to auto-reset the chip after flashing…

In comparison to the CH340G, which also required a crystal oscillator, but provides all the modem control signals, which, are usually not even broken out, the CH340N made much more sense.

PCB Bottom.

A power LED, as well as an indicator LED on pin 7 was also included.

Assembled PCB, Top Layer.

Assembly and Soldering

I normally assemble all my projects by hand and reflow-solder them with a hot plate. for this project, I decided to do things a bit differently, which ended up being a bit awkward, but still resulted in a perfectly useable PBC.

As you will know by now, I only do written articles, as I don’t consider myself ready for the Youtube and video thing, as well as because I believe a well-written article, with detailed pictures, is easier to understand than a video…

Well, today, we will have both… This article, with its writeups and pictures, as well as a short assembly and soldering video, with no sound, sped up 5x, as I did not want to bore anyone with a 25-minute silent video…

Let us begin then…

PCB and Stencil

We start with a blank PCB and the laser-cut stainless steel stencil that I got from PCBWay.

Solder paste applied

Solder paste is then applied with the stencil and a scraper, and afterwards, the stencil is removed… The PCB is now ready for component placement…

From here on, we will go to the video footage… showing component placement, with some awkwardness due to the camera being in the way, as well as hot-air soldering, with the same awkwardness, as I was forced to use my right hand ( I am left-handed), not to block the camera view…

Begin quite new to the video thing, I have also not quite figured out the editing software, so the video is in native resolution… not zoomed…

After assembly

After assembly, I checked for solder bridges and was quite happy that there were none. This also meant that the board worked perfectly the first time around… as it should…

Order your own version of this development board

Manufacturing

I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ) , or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Picture Gallery