“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…

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…

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.

8Ch NMOS Breakout Module

As a companion module to my recently published 8Ch PMOD breakout board,
I decided to do a similar PCB, but with NMOS devices instead. This opens up more possibilities for proper testing and prototyping, as PMOS and NMOS devices has different use applications, and most importantly, can sometimes even be combined for a particular purpose, like an H-Bridge motor driver, for example.

8Ch NMOS Breakout

What is on the PCB?

As NMOS devices function quite differently from their PMOS counterparts, it did not make sense to reuse the PMOS board, and just change the devices… although some people may be tempted to think you could…

The N Channel Mosfet basically “works in mirrored mode” from a P Channel one, and is used to do so-called ” LOW Side switching” which means that your load connects to the positive power rail, and then to the DRAIN pin of the MOSFET, with the source being connected to ground… ( It can sometimes also be used the other way around… but lets not go there now….

The current prototype PCB contains 8 BSS138 NMOS Mosfets, in my case, with is capable of about 800mA of current… All source pins are internally connected to ground. This forces you to use this module as a low side switch…

Two 10-way 2.54mm headers are provided, with a ground pin on Pin 1 and 10 of each of these.

The Drain pins of each NMOS device is available on the top header, labeled D1 through D8, and the Gate pins of each respective NMOS device is available on the bottom header, labelled G1 through G8.

Each gate has a pull-down resistor to ground, to keep it from flapping around, as well as a gate resistor. In my case, I selected to use a 10k pulldown, and a 1k gate resistor, as that is sufficient for my general needs…

Each NMOS device also has a LED signal indicator, to assist in visual confirmation of a specific channel’s state.

PCB Top Side

The Schematic

Schematic

Using the breakout

The module is very easy to use, and as briefly mentioned above, you are only required to connect one side of your load to the positive supply rail, and the other side to the drain pin of your choice.

Connect the ground pins of the module to your ground rail.

The Gate pin, with a corresponding number to the drain you have selected, can now be connected to your GPIO of choice on a microcontroller.

Drive the pin High to switch on the load, drive it log to switch off. Easy.

Please note: While the NMOS devices used on the board can handle quite a lot of current, (800mA in the case of the BSS138), it is not recommended to try and pull too much current through a single channel. The PCB traces can safely handle about a maximum of 300 to 400mA per channel.

PCB Bottom

Manufacturing

The PCB for this project has been manufactured at PCBWay.
Please consider supporting them if you would like your own copy of this PCB, or if you have any PCB of your own that you need to have manufactured.

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Example code for using the breakout (Arduino)

// Example code for 8Ch NMOS breakout
int Gate1 9;
int Gate2 10;

void setup() {
  // drive the two gate pins low to ensure NMOS devices
  // are in a positively known state at startup
  digitalWrite(Gate1,LOW);
  digitalWrite(Gate2,LOW);
  // Set gpio to output mode
  pinMode(Gate1,OUTPUT);
  pinMode(Gate2,OUTPUT);

}

void loop() {
  // Toggle the two channels in an alternating pattern
  digitalWrite(Gate1,!digitalRead(Gate1));
  digitalWrite(Gate2,!digitalRead(Gate1));
  delay(1000);  

}

8-Ch P-Mos Breakout

While prototyping our projects, we Makers often need to interface devices with a higher current draw, like motors, or RGB lights, to our microcontrollers. These typically are unsuitable for connecting directly to an Arduino, ESP32 or Raspberry Pi’s GPIO pins. This is usually the time when we start grabbing transistors or MOSFETs.

While I normally keep a few leaded transistors and MOSFETs in the lab, These are not always convenient to use, as they may be in big packages or have the wrong specifications for the task that we are trying to perform.

SMD versions are more common in my lab, but they come with the problem of being small, and also completely unfriendly to the breadboard environment.


I have thus been playing with an idea to make a series of dedicated breakout boards for just this purpose. Having an easy way to test a specific MOSFET for a design, and having more than one of them handy, without all the wiring issues, and using the bare minimum of those DuPont wires!

I came up with the following prototype, which, while not completely optimised yet, already makes things easier. The breakout board provides 8 P-Channel Mosfets, with a single source connection, and individually broken-out Drain and Gate pins.

LED indicators on each channel provide a visual indication of the status of each P-Mos device, and the breakout can also be mounted directly into an enclosure if needed.

What is on the PCB?

Each channel comprises a P-Channel Mosfet, in this case, a SI2301, which has a suitably low gate voltage, a pullup resistor on the gate, to keep it from floating, a status-indicating LED and a current-limiting resistor for the LED.

No gate resistor was added, as this would change depending on the actual MOSFET, as well as the microcontroller that you use. The Gate pullup resistor can also be left unpopulated, in case you need to do something specific there.

Two rows of 10-way, 2.54 header pins are at the top and bottom of the PCB, to make using the breakout on a breadboard possible.

The Pinouts are as follows

H2 – Top V+ D1 D2 D3 D4 D5 D6 D7 D8 GND
with Dx corresponding to the Drain pin of each MOSFET. All the Source pins are internally connected together, as I assumed that I will use the same source voltage on each channel anyway.

H1 – Bottom V+ G1 G2 G3 G4 G5 G6 G7 G8 GND
with Gx corresponding to the gate pin of each MOSFET.

V+ and GND for each header is internally connected, to make it possible to supply V+ and Gnd on any of the two headers.

PCB Top Layer

The Schematic

Schematic

Using the Breakout

Using the breakout is straightforward. Connect a source voltage to either of the V+ pins and Ground to either of the GND pins. ( the ground is used internally for the status LEDs)

Connect your load, with the positive to a drain pin, let us say D1, and the load ground to your breadboard, or power supply ground. Connect the corresponding gate pin, in our case G1, to the microcontroller pin of your choice, through a suitable gate resistor, and pull it high at setup, to ensure that the MOSFET stays off. Pull low to activate as needed.

Please note that you should not try to switch excessively large currents through a single MOSFET Channel, as the PCB traces can realistically only handle approximately 300 to 400mA per channel.

Note 2: If you are driving an inductive load, it is considered good practice to add a flywheel diode on the load as well. This will protect the MOSFET from back EMF when the MOSFET is switched off.

PCB Back

Manufacturing

The PCB for this project has been manufactured at PCBWay.
Please consider supporting them if you would like your own copy of this PCB, or if you have any PCB of your own that you need to have manufactured.

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Example code for using the breakout (Arduino)

// Declare Gate driving GPIO pins
int gate1 = 10; 
int gate2 = 11;


void setup() {
// Set the GPIO pins as outputs and drive them HIGH
// This keeps the channels switched "OFF"
  digitalWrite(gate1,HIGH);
  digitalWrite(gate2,HIGH);
  pinMode(gate1,OUTPUT);
  pinMode(gate2,OUTPUT);

// Writing to the GPIO's before setting their pin Mode,ensures that the
// GPIO's are in fact initiated in a know correct state.

  Serial.begin(115200);

}

void loop() {
// In the loop, we just toggle the GPIOs, thus
// alternatively switching the channels on or off
  digitalWrite(gate1,!digitalRead(gate1));
  digitalWrite(gate2,!digitalRead(gate1));
  delay(1000);
  }

RP2040 Scoppy Oscilloscope Analog Front End Shield

This post will look at my prototype Analog front-end for the Scoppy RP2040 Oscilloscope. It is important to state right from the beginning that this circuit is one of the 5 recommended designs from the Scoppy Website. I have only moved it from the breadboard design as published, onto a PCB.

The entire circuit, with all of the original designer’s writeups, is available here

So, why use someone else’s circuit? Well, the reason for this is two-fold.
1) The circuit designer also designed the firmware, so it stands to reason that his circuit will be optimised for use with the firmware.
2) Using his circuit provides a solid reference, making it possible to test the firmware for correct operation, and later on, providing a base for my own design – if and when I do decide it is worthwhile to actually design my own.

As I already have a proper oscilloscope as well as a logic analyser, this entire exercise is purely academic, I find the Scoppy project interesting, and as such, I would like to see how it compares with my commercial products ( while also knowing that it won’t be a very fair comparison ).

With all the limitations, I am however still quite impressed at the level of use that you can get out of this very simple device. It is definitely quite useful for a beginner.

What is on the PCB, and what did I change?

The PCB is a dual-layer shield that is designed to be used with the MakerIOT2020 Raspberry Pi Pico Carrier board. The shield is directly powered by the carrier board.

The original Analog Front-End #3 circuit featured a single channel input, capable of accepting a -18.0v to 18.0v signal input.

My changes were limited to doubling up on that circuit, to provide two channels.

The Schematic


I have redrawn the original schematic, partly to make it easier to understand for myself, as well as to help me with the design of the PCB.

Lets take a look at the schematic ( by using text from the original designer)

The author makes no warranty, representation or guarantees regarding the suitability of this design for any particular purpose. Nor does the author assume any liability arising out its use and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.


All text below is quoted from here

This design builds on Design 2 and adds over and under voltage protection to the analog front end. After all, we won’t have a cheap oscilloscope if we keep frying our components!

I’m assuming here that the minimum and maximum voltages that will be applied to the input of the scope will be -18V and +18V respectively. It has been tested from -18.5V to 18.5V (two of my 9V batteries in series) but of course If you decide to use this design you are doing so at your own risk. I personally wouldn’t use Scoppy with an expensive phone/tablet just in case something unexpected goes wrong (better to use an old, obsolete phone that is no longer used for anything else) – especially when dealing with higher voltages – but of course you can do what you like.

Protecting the Op-Amp input(s)

First of all we need to protect the op-amp. In this design we’ll be using an LM324 op-amp, which is very similar to the LM358 but contains four individual op-amps rather than two. We’ll be using three of these op-amps. The reason for this will be explained later.

According to the datasheet for the LM324 the allowed input voltage range goes from -0.3V to 32V. Of course 32V is above the maximum expected voltage (18V) and so we don’t need to worry about over-voltage protection. However we do need to ensure that the voltage at the input pins don’t go below -0.3V. A schottky diode can be used to clamp the voltage to something above -0.3V (D1 in the schematic).

One thing that needs to be considered when selecting the diode is its reverse current. The 1N5817 has a very low forward voltage but high reverse current and this results in a voltage drop at the input of the op-amp (in the order of 100mV). Presumably this is because it draws current through the high value input resistor (Rg1). The 1N5711 has a much lower reverse current specification and I couldn’t discern any voltage drop when this was inserted into the circuit. However, its forward voltage (at the current expected in this part of the circuit) is very close to the minimum allowed voltage of -0.3V. To be safer I prefer to use something like a BAT46. It does result in a voltage drop of a few millivolts but the clamped voltage is more like -0.23V.

Protecting the Pico/RP2040

The Pico datasheet states that:

the ADC capable GPIO26-29 have an internal reverse diode to the VDDIO (3V3) rail and so the input voltage must not exceed VDDIO plus about 300mV

The obvious way to protect the ADC inputs (GPIO26-29) then is to simply insert a schottky diode between the ADC input and VDDIO. However, the RP2040 datasheet says that:

the voltage on the ADC analogue inputs must not exceed IOVDD ...<snip>... Voltages greater than IOVDD will result in leakage currents through the ESD protection diodes

That suggests to me that we shouldn’t be allowing current to pass (leak) through our clamping diode and into IOVDD. I could be completely wrong here – if you think so then please share your thoughts in the forum (Discussions).

Anyway, to be safe we’re going to avoid that situation by sending the current to the output of one of our op-amps (LM324-sink on the schematic). The LM324 is able to sink up to ~10mA so this should work fine if we limit the current from the main op-amp (LM324-amp in the schematic). Given that the maximum voltage expected at the output of LM324-amp is around 4.5V (Vcc – 1V) then we need a resistor of at least 120R to limit the current to 10mA (4.5-3.3 / 0.010 = 120). A 220R resistor should do fine (Rout).

And of course the reason we are using an LM324 rather than the LM358 of the previous designs is that three op-amps are required.

A 1N5817 diode (D2) is used here (rather than a BAT46 – used on the input of LM354-amp) because at the expected maximum current of 10mA the forward voltage drop of the BAT46 is higher than 300mV. The high reverse current of the 1N5817 is not such an issue here because Rout has a low value and so there will only be a small voltage drop across Rout when D2 is reverse biased.

Construction

Schematic
Breadboard

Here are some instructions for assembling this front end on a breadboard. The pin numbers refer to the LM324 PDIP package. Refer to the schematic and breadboard image above. NB. The rail labelled 5V on the schematic is actually VSYS which of course is not necessarily 5V because it depends on how charged the battery is on your Android device.

Connect 3V3 of the Pico to the top red power rail of the breadboard. Connect VSYS to the bottom red power rail. Connect both ground rails of the breadboard to one of the GND pins of the Pico. The fuse as shown in the breadboard image is optional.

Connect the Vcc pin of the LM324 to the VSYS rail. Connect the GND pin of the LM324 to the GND rail. Don’t connect anything to the ADC pin(s) of the Pico yet.

Now we’ll configure each of the 4 op-amps of the LM324 in turn.

Op-amp 2 – Unused
Op-amp 2 (pins 5, 6 and 7 of the PDIP package) is not used so we’ll wire it up as recommended in the TI tech note – How to Properly Configure Unused Operational Amplifiers.

The voltage at the non-inverting input should be approximately VSYS/2 and the output should be the same.

Op-amp 4 – Vref
Wire up this op-amp as shown in the schematic. The voltage at the output should be approximately 1.65V.

Op-amp 3 – sink
Wire up this op-amp as shown in the schematic. The voltage at the output should be 3.3V.

Op-amp 1 – amp
Wire up this op-amp as shown in the schematic, including the under-voltage protection diode on the input (D1) and the current limiting resistor (Rout) and over-voltage protection diode (D2) on the output. Don’t connect the output to the Pico yet.

Testing and initial operation

You should now be able to safely apply any voltage at Vin1/Vin2 of between -18V and +18V. Test that the voltage at the input of the LM324 (Vampin) doesn’t go below -.3V and the voltage at the output of op-amp 2 after Rout (Vadc) doesn’t go above 3.6V.

Once you’ve confirmed that all of the op-amps have been wired correctly you can connect the output of Rout to the ADC pin of the Pico.


The author makes no warranty, representation or guarantees regarding the suitability of this design for any particular purpose. Nor does the author assume any liability arising out its use and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.

Designing the PCB

PCB Design and Layout

Manufacturing the PCB

The PCB for this project has been manufactured at PCBWay.
Please consider supporting them if you would like your own copy of this PCB, or if you have any PCB of your own that you need to have manufactured.

PCBWay

Assembly

The PCB was assembled with help of a stencil to ease and speed up the solder paste application. The components were then hot-air soldered.
As this is only a prototype, I chose to only place 2.54mm header pins on pins that are required for operation, as well as all the ground pins, to ensure a proper ground plane.

SMD Stencil to speed up assembly

Conclusion

This was quite an interesting project. While everything works as expected, resolution and frequency are limited. ( of course, it is…) The project is however still useful, and will definitely give you some useful results in a pinch.

The logic analyser is by far more useful, but once again, a commercial device will be way more accurate and useful for professional use. Hopefully, the designer will add some protocol filters etc in future.

This device will not replace a proper oscilloscope or logic analyser, but it will definitely give enough accuracy and resolution on low-frequency applications to satisfy some of the basic needs of a beginner or student just starting out with electronics.

It is also important to note that you should be safe, and not try to connect this to high voltages etc. Also, don’t connect this to your expensive phone or tablet, use an old one instead, as accidents may happen, and we don’t want to damage our valuable handheld devices…

An Easy RP2040 Logic Analyzer Shield – Scoppy Scope Part 2

Scoppy Scope Logic analyser Shield with Logic Probes

As part two out of a series of three articles (part 1), This is the Scoppy RP2040 Logic analyzer shield, for use with our Raspberry Pi Pico Carrier board and the Scoppy Oscilloscope firmware for the RP2040.

In Part one, we took a very quick look at the installation of the firmware, as well as the basic limitations for use of this very useful project.

In this part, I want to take a quick look at my Logic Analyser shield, for use with this project, as well as the Raspberry Pi Pico Carrier Board. In part one, we saw that the logic analyzer inputs are limited to 3.3v by the RP2040 GPIO pins. This shield is a prototype attempt to overcome those limitations by using logic-level conversion.

What is on the PCB ?

The PCB is designed to be an add-on shield for the Makeriot2020 Raspberry Pi Pico Carrier Board. (Get your own here) It is in the same form factor as the Arduino Uno shields, but with pinputs specific to the RP2040 and Raspberry Pi Pico.

8 Ch Logic analyser Shield for use with Scoppy and MakerIOT2020 Pico Carrier Board

All Raspberry Pi Pico pins are broken out and labelled, as well as all of the pins specific to the Scoppy App have been clearly labelled. The board are stackable onto the Pico Carrier board, via standard 2.54mm Male Headers, or extra long, stackable female 2.45mm headers, similar to those found on common Arduino shields.

The use of stackable headers will allow simultaneous use of the logic analyser shield and the Analog frontend shield, introduced in part 3 of this series.

In addition to that, a 2×8-way 2.54mm Male header provides access to the 8 logic converted logic analyser inputs.

Logic conversion is done with a simple circuit, comprising a Bss138 N-Channel Mosfet and two 10K resistors per channel.

The shield is powered directly from the Pico Carrier board, which is in turn powered from the OTG cable to the Android Phone or tablet used to display the captured data. ( see Part 1 for installation instructions and other details regarding the Scoppy Project)

The logic level converters allow the use of a 5v logic signal, which is an improvement over the original design, which allowed only 3.3v inputs.

The Schematic and PCB Layout

Logic analyser shield schematic


PCB Layout

Manufacturing

The PCB for this project has been manufactured at PCBWay.
Please consider supporting them if you would like your own copy of this PCB, or if you have any PCB of your own that you need to have manufactured.

PCBWay

Some more pictures of the device

Installation instructions (repeated from Part 1)

Scoppy Scope Installation

All credits for the development of the Scoppy firmware goes to fhdm-dev. This shield is a modification made by MakerIOT2020, and thus belongs to me. In the spirit of the original project, It will however be released to the public as a free open-source project ( free as in free download, free schematic, free design ). The PCB manufacturing files will be made available for free at a later stage, or can be ordered from PCBWay from this link

RP2040 Oscilloscope and Logic Analyser

Oscilloscopes and Logic analysers are essential instruments for every serious electronics hobbyist. They are however quite expensive, and thus beyond the reach of many people starting out with electronics. Today, I will show you a cheap solution, an RP2040 Oscilloscope and Logic analyser…

Before we get started, we need to clear up a few things first:
1). This is not my own project. It was designed and built by someone else.
2). This is not a professional grade Oscilloscope or Logic analyser
3). The range of input voltages, as well as the frequencies that you can measure, are limited.

What is this, and why do I bother with it?

This post is about the Scoppy Occiloscope Firmware, designed by fhdm-dev. I have no affiliation with him/her, I came across this recently and found it useful in the sense that it may help others gain access to instrumentation to greatly help them with electronics.

I did design some derived pcb components that works with this project, in order to take care of some limitations that I saw in the original project. More on that in two follow-up posts, in which I will show you two PCB’s that I designed to use with this project, and analog Frontend ( based on a public design by fhdm-dev, as well as a Logic analyser shield, of my own design

before we do this, we need to look at the basic Scoppy design and its firmware.

Getting Started

You will need a few things to make use of this project, the most important will be the Scoppy App ( available from the Google Playstore ), and an Android Phone.
You will also need a USB OTG Cable/hub for the phone, as well as a Raspberry Pi Pico or Pico W

The Installation and Getting Started Guide is very well documented, and as such, I will not spend a lot of time on that.

My own Setup

I have decided to use my own Raspberry Pi Pico Carrier board for this project, as it will allow me to get away from the breadboard, as well as serve as a platform for easily expanding on the project via expansion shields, as you will see in later articles.

Makeriot2020 Raspberry Pi Pico Carrier Board

This PCB, in Arduino Uno form Factor, will make putting the entire project into a case quite easy, as well as hopefully keep the number of floating hookup wires to a minimum. ( hopefully reducing some notice and other stray signals from interfering too much with our signals)

After installing the application, which is quite easy, we need to load the firmware onto the RP2040. This is also extremely easy is you follow the guide at the top.

Please note that the Android app has two modes, a freeware mode, limited to one channel, and a paid version, with no limitations. I recommend that you consider buying the paid version, as it only costs a few dollars ( I paid $USD2), and will motivate the developer to keep working on the project, and improving it.

Scoppy Application, Main Interface – Oscilloscope
Scoppy Menu
Scoppy Logic Analyser Screen

As we can see, the interface is quite clean, and easy to use.

What are the limitations?

There are quite a few limitations, namely frequency and voltage input.
From what I can understand, the frequency limit seems to be around 25Khz, with the voltage level limit being 0.0v to 3.3v ( as per the limit of the RP2040 ADC

Please make sure that you follow all instructions on the original page, as you can very easily damage your Android device as well as the Pico if you apply a voltage outside of the allowed range.

On the logic analyser side, It is also important to note that you should stay in the 0.0v to 3.3v range of the Pico GPIO’s.

While these limited ranges will definitely limit what you can do and measure, It will still be a very useful project. In the next part of this article, I will show you how I have solved the logic analyser voltage range issue… Allowing you to analyse 5v signals as well.

RaspberryPi Pico Carrier PCB

The Rp2040 chip from the RaspberryPi foundation should be quite well known to everybody by now. Many companies have also released their own development boards based on it. The original Raspberry Pi Pico is popular, based on its small size.


For myself, there is however a serious drawback, its small size, while perfect for breadboard, made it necessary for the developers to place the pinouts on the back of the board. This makes it necessary to either memorise the pinouts or always have a pinout diagram handy when working with it.

The module also comes with castellated holes, making it ideal to place onto a custom PCB as a “component”. This got me thinking, I can easily design a custom RP2040-based PCB, but manually assembling the tiny RP2040 is something that my poor eyesight will make a bit challenging (staring at computer screens for many years does really take its toll as you get older).


Finding components in stock (excluding the RP2040) is also a challenge in my area.

This made me think about taking a popular footprint ( like the Arduino Uno ), and placing a Pico module directly onto the board, labelling all the pins clearly on the front, and installing female headers to access them.

While it is obviously not a very complicated PCB, it will definitely help me to utilise the fantastic little chip more effectively.

Assembling the PCB should only take a few minutes, as you only have to solder the pico and female header pins to the board. When completed, it should look like this:

If you have already soldered headers to your Pico, you can still use this PCB as well. You can also use the new Pico W with this board, the only difference is that the Pico W does not have castellated holes on the pins, so you would have to use header-pins. Also, the debug port now has a connector, so you will have to use the port directly on the Pico for that.

A good introduction to the new Pico-W can be found here. I have not bought any yet, so have no pictures to show, or comments to make on its operation.

What is next

I have plans to start designing a series of add-on shields with specific functions for this platform, since being freed from the breadboard, the Raspberry Pi Pico suddenly became much more interesting to me.

While smaller seems to be better in the electronics world of today, breadboarding, in my humble opinion, is quite aged, and can be extremely unreliable, due to poor connections etc. It is however very quick and fast, without requiring you to solder anything.

I am thus attempting to get the best of both worlds, by not being tied down to a breadboard, but with the freedom to go there if I choose, or just designing and using a custom shield of my choosing.

Manufacturing

Over the past eight years, PCBWay has continuously upgraded their MANUFACTURING plants and equipment to meet higher quality requirements, and now THEY also provide OEM services to build your products from ideas to mass production and access to the market.


The PCB for this project has been manufactured at PCBWay.
Please consider supporting them if you would like your own copy of this PCB, or if you have any PCB of your own that you need to have manufactured.

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