PWM Controller with R/E

Last month I spent quite a lot of time on expansion modules for use with the ESP-12E I2C Base Card. While the system worked exceptionally well as a prototyping and firmware testing platform ( as originally intended ), I immediately saw that the physical size of everything ( base board, with the cards) would be a problem inside any enclosure, when used with a real-world project.

At the same time, I have an ongoing need to design and manufacture a device for a friend, that will have very limited space inside the enclosure due to other essential components.

I have thus decided to combine the functionality of two of the IO Expander cards into a more compact design, on a single PCB ( Which I plan to use to power and control an Air Assist blower on my desktop CNC/Laser cutter, as well as function as a next step prototype for my other project.

The PCB

Let us take a quick look at the PCB.

Starting from the top left, we have the Blower/Fan Header.
This supplies 12v DC to the Blower/Fan motor, as well as the PWM signal to control the speed. ( Level converted up from 5v DC to 12V, and then reduced to 3.3v ) This may seem strange.

Let me explain for some more clarity…
The PWM input on the Blower/Fan is internally pulled HIGH to 12v ( by the motor driver circuitry – I can not change that, as it is a commercial unit.) The datasheet however calls for a 0v to 3.3v PWM signal to control the speed.

There is also a further input from the fan, which is a pulsed speed indicator (Fan RPM). This signal is 5v.

Next to that header, is a UART Header, with Rx, Tx and DTR signals, with a ground. I do no longer add USB-to-UART chips to my designs because they are not used a lot, take up unnecessary space, and I tend to program with ICSP anyway.

On the right of that, (Red/Blue/Yellow Header) are 5v, Gnd and 6 Analog inputs(A0-A3, A6,A7) [A4 and A5 being used for I2C]

The ICSP programming header is below that,
with a jumper to select PCF8574 interrupt on Pin D2 or not

This is followed by 6 GPIO (P2-P7) from the IO Expander, and
additional GPIO (D10, D11, D12, D13) , as well as (D7,D8,D9) [To be used with a Rotary Encoder]

Another 6way Ground header, as well as the 12v input (red), follows.

Finally, we have J1 and J2, which will switch 12v through BSS138 Mosfets to control static speed 12v cooling Fans (Only one of these is PWM capable)


The 2 Relays are optically isolated from the controller and mains isolation cutouts are provided to further keep DC and AC voltages well away from each other. [ they really don’t play well together, don’t they ?]

This wraps up the quick PCB description.

Schematic

The Schematic is below, along with a download link ( zip format, with PNG image files)

Some more pictures

I use stencils with almost all of my SMD assembly. It saves a lot of time, makes for even solder paste application, and prevents the mess associated with applying solder paste with a syringe, or even worse a skewer-stick or something similar. They do cost extra though, but I find it well worthwhile in comparison to the mess and time that they save.

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.

PCBWay

If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5 USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

4) Click on PCB Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

Using a Rotary Encoder

As part of an ongoing project, I recently designed an expander card for my ESP-12E I2C Base. I am referring to this device( Atmega 328P Base PWM Controller Card). At the time of writing that article, I have not released any of the code for the project. This is a very short post, showing one possible way to implement a rotary encoder onto that particular device. (It can also be adapted for other devices, of course)

Arduino Style Code for using a rotary encoder

// Constants and Variables
const int encFWD = 8;
const int encREV = 7;
int aState;
int aLastState;
int encDir;
int encTurned = LOW;
int encLastState;
int encValue = 0;
int lastEncValue;
const int encInc = 10;

unsigned long lastEncDebounce = 0;
unsigned encDebounceDelay = 50;
const int encBtn = 9;
int encButtonState;
int lastEncBtnState = LOW;
int EncBtnValue = LOW;
int encBtnState;

void setup() {
  //Rotary Encoder
  pinMode(encFWD,INPUT_PULLUP);
  pinMode(encREV,INPUT_PULLUP);
  pinMode(encBtn,INPUT_PULLUP);
  // Init the pins in UNPUT Pullup Mode
  encTurned = LOW; // Flag for encoder

  encLastState = digitalRead(encFWD);
  //Serial
  Serial.begin(115200);
  //Status LED on D13
  pinMode(13,OUTPUT);
  digitalWrite(13,LOW);
}

void loop() {
  lastEncValue = encValue;
 //Handle the Encoder Push Button
 encBtnState = digitalRead(encBtn);
 if (encBtnState != lastEncBtnState) {
    lastEncDebounce = millis();
 }
 if ((millis() - lastEncDebounce) > encDebounceDelay) {
    if (encBtnState != encButtonState) {
        encButtonState = encBtnState;
        if (lastEncBtnState == LOW) {
          EncBtnValue = !EncBtnValue; // Toggle the button Value
        }
    }
 }
 lastEncBtnState = encBtnState;
 // Handle the Rotary Encoder Dial
 aState = digitalRead(encFWD);
 if (aState != aLastState) {
    if (digitalRead(encREV) != aState) {
       if (encTurned == LOW) {
          encLastState = encTurned;
          encTurned = HIGH; // Set Flag
// Setting this flag will get rid of double value entries caused by contact
// bounce inside the encoder. I found it easier to implement this way
// as opposed to using software debouncing as with the button

       } else {
          encTurned = LOW; // Set Flag low
// This will ensure that the value is increased only once per "click"
       }
       if ((encValue < 300) && (encDir == 0)){
          if ((encLastState == LOW) && (encTurned == HIGH)){
            encValue = encValue + encInc;
            encDir = 1;
          }
       }
      
    } else {
      if (encTurned == LOW) {
        encLastState = encTurned;
        encTurned = HIGH;  
      } else {
        encTurned = LOW;
      }
      if ((encValue > 0) && (encDir == 0)){
          if ((encLastState == LOW) && (encTurned == HIGH)){
            encValue = encValue - encInc;
            encDir = 2;
          }
      }
    }
    encLastState = encTurned;
}
aLastState = aState;
encDir = 0;
// Print Some Status
if (encValue != lastEncValue) {
  Serial.print("Encoder Value Changed from ");
  Serial.print(lastEncValue);
  Serial.print(" to ");
  Serial.println(encValue);
}
digitalWrite(13,EncBtnValue);



}

I hope that this will be useful to somebody.

ATMega 328P Based PWM controller Card

As part of my recent ESP-12E I2C Base Board project, I designed an ATMega 328P Based PWM controller card, that can be used as an add-on card with the existing project, or standalone as a custom Arduino Nano compatible development board.

What is on the PCB?

The PWM controller card contains standard Arduino Nano circuitry running at 16MHz, without the USB to Serial converter, as well as a 3v to 5v level converter on the I2C port ( A4 and A5 ), as well as another 12v to 5v level converter, with a build in resistor-divider circuit, used to drive a 12v blower with 3.3v PWM control circuitry.

All analog inputs are broken out to make attaching additional sensors easier.

All the other unused GPIO pins are also broken out, either directly to headers on the PCB (D6~,D7,D8,D9~), D11,D12,D12 (ISCP Header) and D3 ( Marked RPM on the Fan Header)

Most of these pins are also additionally broken out onto the 2x20p female header at the bottom of the card ( See schematic for more details)

The board is designed to be powered from 12v DC (via the VIN pins on the 2x20p header) which is internally regulated down to 5v via an LDO voltage regulator.


External 3.3v should also be supplied to the 2x20Pin header to enable the I2C level converters on the same header. I2C is not directly broken out onto the PCB in this version of the PCB.

A reset button, and power led, as well as the standard led on D13 is also provided.

Manufacturing the PCB


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.

PCBWay

If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5 USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

4) Click on PCB Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

A breadboard friendly MCP23017

I2C port extenders or expanders are extremely useful devices, and I use quite a lot of them in my projects. My go-to device is definitely the PCF8574, mainly because it is sort of “breadboard friendly”. The MCP23017, with the existing breakouts available locally, are not. I have thus decided to design my own version of a breadboard friendly MCP23017 breakout board.

The Breakout Module PCB and its features

A breadboard friendly MCP23017 breakout board – Front
a breadboard friendly MCP23017 breakout board – Back

While this was definitely one of my easier projects, It still took a bit of time to get it just right and add some essential components and features directly onto the PCB.

The main features of this breakout:
– DIP12 Layout – with all pins broken out, address pins to jumper headers…
– Proper decoupling capacitors, as close as possible to the MCP23017 chip.
I had to make use of the back layer of the PCB to do this, not exactly ideal, but with proper power and ground planes, and nice thick tracks, I believe they will be just fine.

– Address selector jumpers – The breakouts that are available locally, do not have these.
– Breadboard friendly layout – 33.020mm x 20.320mm [board size], with 15.240mm vertical spacing between the rows of pins, ensures that you can easily fit it onto your breadboard, while still having space to add jumper wires to the pins. Horizontal pin spacing is standard 2.45mm.

The Schematic

The schematic is plain and simple. A few points to note though:
– The address selection header, as well as the io pin headers are not shown on the schematic.
– I2C pullup resistors are set at 1k but can be replaced with more suitable values as required in your circuit

Using the breakout

I have previously written two very detailed articles on using this chip. They are linked below:
Using the MCP23017 with the standard Wire.h library
Using the MCP23017 with the Adafruit MCP23017 library

Manufacturing the PCB

The PCB for this project is currently on its way from China, after having 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 be manufactured.

PCBWay

If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

4) Click on PCB Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

Compact Remote Alarm Transceiver – Part 2

In part one of this series, I took a look at some of my experiments using different voltage regulators, to design and build the Remote Alarm Transceiver prototype, and also mentioned that I will be looking at a single chip logic converter solution. In this (hopefully short) post, I will take a detailed look at that logic converter chip, as well as show you how it is used.

The Logic Level Converter Chip

I have chosen the TXS0108E Bi-Directional 8-bit Logic-Level Voltage translator from Texas Instruments for this application.

Some of the features of the device is listed below:

• AEC-Q100 Qualified for Automotive Applications
– Device Temperature Grade 1: –40°C to 125°C
– Device HBM ESD Classification Level 2
– Device CDM ESD Classification Level C6
• No direction-control signal needed
• Maximum data rates
– 110 Mbps (push pull)
– 1.2 Mbps (open drain)
• 1.4 V to 3.6 V on A port and 1.65 V to 5.5 V on B
port (VCCA ≤ VCCB)
• No power-supply sequencing required – either
VCCA or VCCB can be ramped first
• Latch-up performance exceeds 100 mA per
JESD 78, Class II
• ESD protection exceeds JESD 22 (A Port)
– 2000-V human body model (A114-B)
– 1000-V charged-device model (C101)
• IEC 61000-4-2 ESD (B port)
– ±8 kV contact discharge
– ±6 kV Air-gap discharge

Datasheet description:

This device is an 8-bit non-inverting level translator
that uses two separate configurable power-supply
rails. The A port tracks the VCCA pin supply voltage.
The VCCA pin accepts any supply voltage between 1.4
V and 3.6 V. The B port tracks the VCCB pin supply
voltage. The VCCB pin accepts any supply voltage
between 1.65 V and 5.5 V. Two input supply pins
allows for low Voltage bidirectional translation
between any of the 1.5 V, 1.8 V, 2.5 V, 3.3 V, and 5
V voltage nodes.
When the output-enable (OE) input is low, all outputs
are placed in the high-impedance (Hi-Z) state.
To ensure the Hi-Z state during power-up or power-down periods, tie OE to GND through a pull-down
resistor. The minimum value of the resistor is
determined by the current-sourcing capability of the
driver.

Typical Application:

Reference Design / Typical Application for the TXS0108E

My Thoughts:

I really like the tri-state (high impedance) mode of the chip, as it allows for isolation between the different voltage level circuits, for example, If I were to communicate on a 5v SPI bus, to another device, I can for instance put the chip in Tri-state mode, and not worry about stray signals interfering from the 3v side.

On the downside, the chip is very small, which makes it a real challenge to solder by hand. On the speed side, It is also not quite as fast as my usual MOSFET based circuitry. It does however do the job it was designed for quite well.

Updated Circuit

Integrating the chip into the existing Remote Alarm Transceiver circuit is very easy, allowing us to replace almost all of the Mosfet-based Logic level converters. We do still need a few of them, as we have only 8 bidirectional channels on the TXS0108.

Schematics

Some Notes on the schematics:

A battery level monitor is connected through a voltage divider, with a MOSFET as a switch to the A0 pin. The voltage divider is set up for a 12v DC input source. The MOSFET is controlled from the D6 Pin.

The reason that I did this is, that I found some parasitic voltage leakage through the A2D converter in a previous design, reducing battery life. My hope is that by only reading battery level when the MOSFET is on, there can be an increase in battery life ( Taking into consideration that the Voltage regulators are not very efficient, it won’t really amount to a big gain unless I switch to an SMPS in the future. )

The PCB

Remote Alarm Transceiver PCB
The PCB

In the picture above, we can see the completed PCB (The relay and buzzer were not populated yet)

Manufacturing the PCB

PCBWay

This PCB was manufactured at PCBWAY. The Gerber files and BOM, as well as all the schematics, will soon be available as a shared project on their website. If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

4) Click on PCB Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

Compact Remote Alarm Transceiver – Part 1

As part of my experiments with LoRa and the easy to use ATMega328P, I have recently designed quite a few LoRa based projects. In this final 2 part series, I will look at two additional projects, part of a Remote Alarm Transceiver, where I experimented with a changing a few things:

– Using LM317G adjustable voltage regulators.
– Replacing my standard N-MOS based logic level converters with a dedicated chip.

Remote Alarm Transmitter
LoRa Remote Alarm Transmitter – with Onboard Relay putout and two sensor inputs

How does this differ from my other LoRa Based projects?

The PCB presented above does in fact not really differ a lot from any of my existing LoRa based projects.
However, there are a few subtle changes, mainly experimental changes, brought on by factors such as component availability and an attempt to reduce component counts and board size.

The first of these changes is using the LM317G voltage regulator, in the place of my usual LM1117 3.3 and 5.0 LDO regulators.

The LM317 is an old device, It has been on the market for a long time. It can supply up to 1.5A of current, and a single device can be configured to supply a wide range of different voltages by just changing two resistors. This seemed quite attractive to me, as it is getting quite difficult to reliably get quite a few components on time, and with decent pricing in the post-Covid-19 world.

The second major change would be moving away from my existing N-Mos based Logic converter setup, where I used the BSS138 and 10K resistors as logic converters. This setup works perfectly, but it has the drawback of requiring quite a lot of components. for example:

To provide logic conversion to an RA-02 module, with access to all the IO Lines (GPIO0-5 included) required 12 BSS138 Mosfets and 24 10k resistors. This is quite a lot of components. A dedicated logic converter chip would thus be a much more attractive solution.

Driver circuitry for sensor Inputs, consisting of a simple transistor input, and an optically isolated Relay output completes the circuit.

Using the LM317

LM317 Typical use circuit - Fixed Voltage

The output voltage of the LM317 is typically set using two resistors, with a suitable current rating, using the following Formula

VOUT = 1.25 * ( 1 + R2/R1 )

It is also common to use a variable resistor at R2, to have fine control over the output voltage. This is due to the fact that stock resistor values do not always give you the exact voltage you require. You should also take into account that using a 5% resistor will be less accurate than a 1% resistor.

The grid below is a list of common stock resistor values for R1/R2, with the resulting voltage produced.

R1 vs R2 Grid for use in selecting fixed output voltage

R2\R1150180220240270330370390470
681.821.721.641.601.561.511.481.471.43
821.931.821.721.681.631.561.531.511.47
1002.081.941.821.771.711.631.591.571.52
1202.252.081.931.881.811.701.661.631.57
1502.502.292.102.031.941.821.761.731.65
1802.752.502.272.192.081.931.861.831.73
2203.082.782.502.402.272.081.991.961.84
2403.252.922.612.502.362.162.062.021.89
2703.503.132.782.662.502.272.162.121.97
3304.003.543.132.972.782.502.362.312.13
3704.333.823.353.182.962.652.502.442.23
3904.503.963.473.283.062.732.572.502.29
4705.174.513.923.703.433.032.842.762.50
5605.925.144.434.173.843.373.143.042.74
6806.925.975.114.794.403.833.553.433.06
8208.086.945.915.525.054.364.023.883.43
10009.588.196.936.465.885.044.634.463.91
120011.259.588.077.506.815.805.305.104.44
150013.7511.679.779.068.196.936.326.065.24
180016.2513.7511.4810.639.588.077.337.026.04
220019.5816.5313.7512.7111.449.588.688.307.10
270023.7520.0016.5915.3113.7511.4810.379.908.43
330028.7524.1720.0018.4416.5313.7512.4011.8310.03

As you can see from the table above, using stock resistors, the output voltage is reasonably accurate, but it is quite obvious that you will need a potentiometer to get exact values.
Another issue will definitely be heat dissipation. In my PCB design, I have used the SOT-223 package of the component, with a PCB heatsink, built directly into the layers. With the LM1117 LDO regulators, these work extremely well.

Logic Level Conversion

In this design, I used my standard Logic Level conversion circuit, comprised of a BSS138 N-Mos with two 10 k resistors. This circuit, although a bit cumbersome with lots of components if you need many logic converters, is very stable, and functions extremely well.

Conclusion

This circuit was designed as a two-part prototype, with the goal of experimenting with different voltage regulators, and in part 2, with a single chip 8 channel logic converter. As such, I do not feel comfortable releasing the full schematics to you at this stage, do so anyway in the interest of learning. The circuit works, but there are many issues with the regulators:



– Overheating at input voltages above 8.0v
The PCB heatsink will have to be improved, or even a different package for the LM317 with the possibility to attach an external heatsink.

– The voltages do not seem stable, especially on the 3.3-volt side.

Manufacturing the PCB

PCBWay

This PCB was manufactured at PCBWAY. The Gerber files and BOM, as well as all the schematics, will soon be available as a shared project on their website. If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

4) Click on PCB Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

Easy to Use RA-02 Breakout Module

Original RA-02 breakout Module, next to improved RA-02 breakout Module

Most Makers and electronics enthusiasts may already know of the RA-02 LoRa Module. Many of them might own an RA-02 Breakout module or two… For those who do, they will surely know about the problems encountered with using this particular breakout module…

The RA-02 module, in itself, is a great piece of kit, and when used on a custom PCB, which was designed with all the little secrets of this module taken into consideration, is a pleasure. Using the RA-02 breakout module, in its existing form factor, does however present quite a few unique challenges, which, if you are unaware of them, can cause quite a few frustrating moments, or even result in permanent damage to the module…

In this post, we will focus on :
1) The Challenges of the existing commercially available RA-02 Breakout Module
2) My Solution to above mentioned Challenges
3)Testing the Module
Maker Uno – An Arduino Uno Clone
Maker Nano RP2040
Maker Pi Pico – Raspberry Pi Pico breakout module


What are these challenges:

1) The module is based on the SX1278 chip from Semtech and is a 3v device. The IO pins are NOT 5v compatible but seem to work for a few hours or so when used with 5v… This causes many people, especially on Youtube, to assume that it is ok to send 5v logic signals to this module…

I have still not seen any Youtube video telling viewers to at least use a resister divider or logic converter… People just don’t know, and those that know seem to be keeping quiet!

Adding logic converters is in fact specified by the datasheet.

2) Adding logic converters means adding additional wiring, and for a breadboard based project, that adds to the complexity.

3) You have a total of 4 ground pins that need to be connected. not connecting all of them, causes funny things to happen, from overheating down to failure… ( My personal experience while researching this project)

4) The existing breakout module is not breadboarding compatible, resulting in a floating assembly with wires going everywhere, which results in unstable connections etc…

Basically something similar to the picture below:

RA-02 breakout Module (original) with Maker Uno and Level converter module

In this picture, I have an existing RA-02 Breakout Module, with an 8 channel Logic converter and an Arduino Uno clone, along with all the needed wiring to make this setup possible… Quite a lot of wires indeed…

My solution:

I design and use quite a few LoRa PCBs and on all of them, I implement logic conversion using the BSS138 N-MOS Mosfet and 10k resistors. It is a cheap and reliable solution, but it can take up quite a lot of space on a PCB, as this means 11 Mosfets and 22 10k resistors if I were to provide level conversion to all of the RA-02’s GPIO and IO pins…

I also have the constant problem of many unnecessary wires, many of which sometimes fail straight out of the box, when prototyping something. I partly solved that by designing a few dedicated PCB solutions, but that is not always ideal,

Using a dedicated Logic Converter IC, and Mosfet based converters to make up the difference, on a breadboard compatible module, seemed like a good idea, so I went ahead and designed the following solution:

RA-02 breakout Module on a breadboard

The breakout board module is breadboard compatible, and also has clearly marked pins to indicate the 3v and 5v sides of the module.

Testing the Module:

Using a 5v device ( Cytron’s Maker Uno )

For my first test, I decided to test with an Arduino Uno Clone, since that is what most Makers and students will have access to. I used Cytron’s Maker Uno platform, which is equipped with some added goodies, in the form of diagnostic LED etc to make prototyping a lot easier.

RA-02 breakout Module, connected to Maker Uno

As we can clearly see, It is only necessary to connect to the 5v logic side of the module, as well as provide 3v and 5v + GND to the module

In this test, I used Sandeep Mistry’s LoRa Library, with the Arduino IDE to do a quick test sketch.

Connections are as follows:

RA-02 Module Maker Uno

MISO D12

MOSI D11

SCK D13

NSS D10

RST D9

DIO0 D2

OE D8

Full code download

Let us look at some important sections though, to thoroughly understand how to use the module:

Pin Declaration

#include <SPI.h>       // include libraries

#include <LoRa.h> // I used Sandeep Mistry’s LoRa Library, as it is easy to use and understand

const int csPin = 10;     // LoRa radio chip select

const int resetPin = 9;    // LoRa radio reset

const int irqPin = 2;     // change for your board; must be a hardware interrupt pin

const int OEPin = 8;     // Output Enable Pin, to enable the Logic Converter

In the Setup function, we need to do a bit of extra work, since our Maker Uno ( or your Arduino Uno ) is a 5v device…

void setup() {

 Serial.begin(115200); // initialize serial

 pinMode(OEPin,OUTPUT); // Setup the OE pin as an Outout

 digitalWrite(OEPin,HIGH); // and Pull it High to enable the logic converter

 while (!Serial);

 Serial.println(“LoRa Duplex – Set spreading factor”);

 // override the default CS, reset, and IRQ pins (optional)

 LoRa.setPins(csPin, resetPin, irqPin); // set CS, reset, IRQ pin

 if (!LoRa.begin(433E6)) {       // initialize ratio at 433 MHz

  Serial.println(“LoRa init failed. Check your connections.”);

  while (true);            // if failed, do nothing

 }

 LoRa.setSpreadingFactor(8);      // ranges from 6-12,default 7 see API docs

 Serial.println(“LoRa init succeeded.”);

}

A comparison, using the standard RS-02 Breakout module, together with one of my own “Arduino type PCB”

ATMEGA328P with 8 Channel Logic Converter.

Original RA-02 Breakout Module, connected to an ATMEGA328P PCB with onboard Level converters

As we can see, you need quite a lot more wires to make this work. It is also worth noting that we have only 8 level converters on this ATMEGA328P PCB, in order to use all of the RA-02’s GPIO, we will need to add an additional external logic converter as well.

Using a 3v Device:

Cytron’s Maker Nano RP2040

For my second test, I decided to be a bit brave, and try to use the new Raspberry Pi Pico ( RP2040 Microprocessor ). I have quite a few of them lying around and have never really done a lot with them, due to the fact that I do not really like using MicroPython or CircuitPython, and also because the recently released Arduino Core for the RP2040 still being quite new… I decided to use a development board that I recently bought from Cytron, the Maker Nano RP2040, as it has all the added diagnostic features to make my life a bit easier, I will also include a test with an original Pi Pico board, to make it more accessible to everyone out there.

RA-02 Breakout Module, connected to Maker Nano RP2040

Once again, I used Sandeep Mistry’s LoRa Library, with the exact same Arduino sketch, used for the Maker Uno test. (I obviously needed to change the pin numbers though, as the RP2040 uses different pins for its SPI interface).

Maker Nano RP2040 RA-02 Breakout Module

NSS 17

MOSI 19

MISO 16

SCK 18

RST 9

DIO0 8

In this case, we DO NOT need the OE pin, as the RP2040 is a native 3v device. The level converter can thus stay disabled, with its pins in tri-state ( high impedance ) mode.

If we look at the code, it is similar to the Maker Uno’s code, with only the Pin declarations needing a change

#include <SPI.h>       // include libraries

#include <LoRa.h>

const int csPin = 17;     // LoRa radio chip select

const int resetPin = 9;    // LoRa radio reset

const int irqPin = 8;     // change for your board; must be a hardware interrupt pin

byte msgCount = 0;      // count of outgoing messages

int interval = 2000;     // interval between sends

long lastSendTime = 0;    // time of last packet send

// Note that SPI has different names on the RP2040, and it has 2 SPI ports. We used port 0

// CIPO (Miso) is on pin 16

// COPI (Mosi) is on pin 19

// SCK is on pin 18

// CE/SS is on pin 17, as already declared above

I did not use a breadboard, in order to make things as easy as possible.

Cytron’s Maker Pi Pico – A Pi Pico on a breakout PCB

RA-02 Breakout Module, connected to Maker Pi Pico

To make things a bit easier, without having to resort to using a breadboard, I decided to do the Original Pi Pico test using the Maker Pi Pico PCB. This PCB is basically a big breakout module, with detailed pin numbers and some diagnostic LEDs, but it also uses a native Pi Pico, soldered directly to the PCB, by means of the castellated holes… So, While technically not being a true standalone Pico, It makes my life easier and was thus used for the test, as I can be sure that the pins are labelled exactly the same as on the original Pico.

The code used for the Maker Nano RP2040 works perfectly, with no changes required.

This post is getting quite long by now, so I have decided not to include my tests of the ESP-12E ( NodeMCU ) or ESP32 development boards here as well… They also function as expected.

In Summary

When I started this project, I set out to solve a problem ( personal to me ), that could potentially help a lot of other people use the RA-02 Module for more projects and tasks. The Breakout module in its current form can also be used with the RA-01h module (915Mhz Module) without any changes. All GPIO pins are broken out, and accessible through full logic converted pins on both sides of the breakout module.

I hope that this will be useful to someone. I am also not releasing the full schematics at this stage, as I may decide to make some minor cosmetic changes in the near future.

The PCB can however be ordered from PCBWay in its current form and works 100% as expected. The BOM file is available with the ordered PCB as usual.

PCBWay Banner

This PCB was manufactured at PCBWAY. The Gerber files and BOM, as well as all the schematics, will soon be available as a shared project on their website. If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

PCBWay Start Quotation Page

4) Click on PCB Instant Quote

PCBWay Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

Quick order PCB from PCBWay

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

PCBWay PCB parameters
PCBWay PCB Parameters - Page 2

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

PCBWay Stencil
PCBWay Checkout

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

Easy to use CAN-BUS Module with Relay, LiPo Battery Backup

Can Relay Module running on battery power

CAN-Bus allows us to add a lot of devices to a single bus (theoretically up to 127, with a practical limit of about 110). It was logical to decide to use CAN-BUS for communication between my LoRa-CAN Module and remote nodes in my ongoing farm telemetry system. In a previous project, I introduced the LoRa-CAN Gateway, which will be used to send/receive messages from the master control unit, the SX127x-RA-02-Module.

Today, I will focus on the design of the node device, an Arduino compatible CAN Relay Module PCB, with a built-in, CAN Controller and Transceiver ( MCP2515 and TJA1050 ), and the option to be powered from a LiPo battery (18650 or Single 3.7v Lipo cell), with charging provided by an MH-CD42 Module, similar to that used in the SX128x project mentioned above. The Module can also be powered directly from up to 12v DC by placing Jumper H2 in the V-REG position…

As mentioned in a previous project, the MH-CD42 module can provide up to 2A of current to charge a battery and provide 5V DC on a direct bypass circuit to power the rest of the circuit while the battery is being charged. This feature makes it ideal for my intended use, as I would only be needing battery power at night when the off-grid solar powered inverter is not actively charging the main batteries, and providing 220v AC.

Can Relay Module Top view

The CAN Relay Module PCB was designed to be as compact as possible, with a total footprint of the standard Arduino UNO. As space was at a premium, and to ensure that there are the absolute minimum additional components that will consume power when operating from the battery, I have not included any USB-to-Serial converters onboard. Firmware can be uploaded with an AVRASp, USBASP, Arduino as ISP or even an external USB-to-Serial converter ( providing that you load a bootloader into the Atmega Chip).

Can Relay Module side view

All of the unused GPIO pins on the ATMEGA chip is broken out into headers, with the exception of D10 ( which is used as CE/SS on the MCP2515 CAN controller), D9 which is connected to the Interrupt from the MCP2515, and D4, which is used to control the onboard Relay.

Can Relay Module with LiPo cell and MH-CD42 Module

The MH-CD42 Module, and LiPo or 18650 Battery are completely optional, The device can function without these, by moving the H2 jumper to the VREG position as already mentioned above. This will divert the DC Voltage(Up to 12v) from the DC input adapter to the build-in 5v LDO voltage regulator to power the device.

If you place the H2 Jumper in the VBAT position, you need to install the MH-CD42 module to provide power to the rest of the PCB, as well as keep the LiPo battery or 18650 Cell charged…

Please NOTE:

When the MH-CD42 module is in use, the total DC input voltage through the DC input adapter SHOULD NOT exceed 5.5v DC! This is a limitation in the operating parameters of the MH-CD42 module. Not paying attention to this will result in damage to the MH-CD42 Module.

You could also power the module with REGULATED 5v DC, directly from any 5v header pin. Please note that in this case,

1) The battery won’t be charged.

2) The LDO regulator will not be in operation.

The Microcontroller

The CAN Relay Module can use any of the ATMEGA8a/88/168/328 AVR microcontrollers, as the pinout is identical. I believe this is an advantage, especially with the current chip prices, where my last quote for an ATMEGA328P-AU was 69$USD!!!! This is in comparison to the 4 to 5 USD each for an ATMEGA8a or ATMEGA168 ( We must also remember though that the 328p is very well known, and thus have higher demand. The 8a/88 or 168 are less well known, have much less memory and flash area, and will thus be cheaper. A word of action though, I had strange issues with I2C on the Atmega8a with Mini core, to such an extent that I2C does not work at all?

If you plan to use I2C on this board, install a 328p right from the start, and save yourself a lot of headaches!

Can Relay Module Schematic Page 1

This is the Relay driver circuit. As you can see, it is optically isolated, and active LOW. This means that you have to pull D4 LOW to energise the relay. Also note that, although the relay is optically isolated from the microcontroller, the coil is NOT galvanically ISOLATED. The load, which is magnetically switched, will be truly galvanically isolated, providing of course that you don’t do something silly like using a common ground to the PCB as a common on the relay…

Can Relay Module Schematic Page 2

This is the Processor and Power-supply schematic. The circuit is basically a standard Arduino Nano, with modifications for the CAN Controller on the next schematic page. Note that the MH-CD42 is not shown on the schematic. The VBAT net connects directly to the VIN pin on the unit, with the BAT net connecting to the positive of the battery. VOUt-5v from the module goes directly to the 5v net. All grounds are commoned.

This is the CAN Controller and Transceiver circuitry. The MCP2515 connects directly to the SPI bus on the microcontroller via D13, D12 and D11, with D10 as CE/SS and D9 as Interrupt or IRQ. It is important to note that although the MCP2515 is a 3v capable device, the TJA1050 Can transceiver is 5v only. This prevents us from running the PCB at 3v unless, of course, we change the TJA1050 out for a 3v capable device…

CODE

The board has been extensively tested with Cory J Fowler’s mcp_can Arduino Library. It works very well indeed.

As I am currently working on the final integration of the two modules, I am not yet ready to publish my final code, showing the operation between the CAN-Bus and LoRa-to-CAN Gateway device in this post. Once I am happy that all issues are definitively sorted out, I will publish my code.

This PCB was manufactured at PCBWAY. The Gerber files and BOM, as well as all the schematics, will soon be available as a shared project on their website. If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

4) Click on PCB Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

I2C IO Module with 4 Relay Outputs and 4 Galvanic Isolated Inputs

Sometimes we need extra Inputs or Outputs on a device, or for use with a project. To implement it properly we also need a lot of additional electronic components to properly isolate these inputs and outputs, with the signals they switch, from our own project, because, let us be real, electronics and electrical devices in the real world do not all work with Arduino or ESP32/ESP8266 save voltages ( 5v and 3.3v ).

I will also tell you about a very special deal to get PCBs of your own made for only one (1) USD ( Including shipping with DHL )! No, I am not joking, and I am not crazy either… More on that later in the post…


It is thus extremely important to have a module that can effectively interface with inputs of 5.5v up to 32v DC ( optically Isolated up to 3000v ), and relay outputs, also optically isolated at 3000v. ( Note that the optical isolation voltage does not mean you can input that voltage level into the chip! It means that it can isolate the electronics on the safe side of the isolator from a voltage spike of up to that voltage!).

I also love using I2C, as it allows me to add modules onto an existing data bus while using only 2 GPIO lines on the MCU!

The module I am presenting to you today was designed to be operated from 5v DC. That includes the I2C data lines (SDA and SCL). If you need to interface to a 3.3v microprocessor, like an ESP32 or ESP8266, or even the new RP2040 or an STM32, you need to use a logic level converter.

The PCB uses the popular PCF8574 8 channel IO expander, which is extremely easy to use, and where you can connect up to 8 devices in a chain ( 16 if you use the PCF8574AT variant as well.. Meaning eight of each variant) This surely adds up to quite a lot of IO lines at a cost of only 2 GPIO on your MCU!

The Circuit diagram is below, and I will discuss each part briefly.

Schematic – Page 1

This is the Galvanic Isolated Input schematic. Each input operates at a voltage of 5.5v to 32v DC. Complete Galvanic Isolation between the Module and the remote input is in effect. Please note that you have to supply a remote ground from the device that provides the input. DO NOT connect the PCB Module ground to an isolated ground pin. This may still work but renders the galvanic Isolation for that input completely useless.


Relay Driver Schematic

This is the Relay driver schematic. Each relay output is driven through an optocoupler, as well as a transistor. Although this arrangement does not provide complete galvanic Isolation of the relay coil, it does protect your MCU from any voltage spikes caused by back-emf when the relay is de-energised. The Relay contacts themselves, being magnetically actuated by the coil, are in themselves Galvanically Isolated from the rest of the PCB.

I2C Control Schematic

Finally, we have the I2C IO Expander schematic, with a 5v LDO regulator, capable of providing up to 600mA of current to the PCB. The PCF8574 Chip’s address is selectable with DipSwitch SW1 so that you can use multiple PCBs at the same time if you should choose to do so. The only note on that is that you should not connect the 5v lines of each individual PCB together. You should also only connect the GND and SDA, SCL lines back to the MCU.

Raw PCB Layout

Earlier on in the post, I promised to tell you about a very special deal…

Well, here it is, as well as some details about the sponsor of this very exciting deal…

PCBPartner.com is owned and operated by Kinji Group, which was established in 1997. We have over 20 years of experience in PCB manufacturing, PCB design, component manufacturing and distribution, PCB assembly and PCB cam software development.

While Kinji Group has 3 PCB factories in China, we have also developed strategic partnerships with more than 15 other factories around Asia. We, therefore, have a large group of specialists in PCB manufacturing, quality control, technical support and part sourcing to support your innovative ideas and products.

Our over 500 employees are spread across 8 branches in Mainland China (Shenzhen, Dongguan, Shanghai, Wuxi, Chengdu, Xiamen), Hong Kong SAR, and Taiwan. And we’re still growing!


We’re confident once you try us out, we’ll become your PCB Partner. And if not? Well, you’ll have scored some free PCB! So why not take us for a spin, you’ve got nothing to lose.

We, MakerIoT2020.com, have decided to give it a go and send this particular PCB to PCBPartner.com for manufacturing. So far, while we are still waiting to receive the PCB, ( Weekends happen 🙂 ), We are very happy with the ease of use of the online ordering system provided.

We would also like to point out that this special order will only be available until the end of March 2022,
as well as that there are a few conditions:

Promotion ends  March 31st 2022
Each new customer can enjoy free PCB on their first order
This promotion applies to
1-2 layers of FR4 PCB, up to 100x100mm, 10pcs, with Green Solder Mask
4 layer of FR4 PCB, up to 50x50mm, 10pcs, with Green Solder Mask
1 layer Aluminum PCB, up to 100x100mm, 10pcs
This PCB promotion cannot be used with other discounts or other promotional activities



For a full list of conditions, and countries that may participate in this offer, please click on the link here

Let us have a look at the entire ordering process..

Once you click on the PCBPartner.com link, you will be taken to their website, where you should sign up, which is free and easy… We used our Google.com account details and were ready to order in seconds…

PCBPartner Start Page

You can now Login with your new credentials ( after registering using this special link ). Then click on the FR4 button to start the order process…

FR4 PBC Quote Form – Before uploading your Gerber Files

Enter the specific details for the manufacturing of your PCB, and upload your Gerber files.

After uploading your Gerber Files.

Continue selecting options for your PCB order…
Make sure to select DHL shipping, to take advantage of the special 1USD option, and click on the ADD to Cart Button…

Quote added to your shopping cart.

You will now get a message that your enquiry has been submitted successfully.

Click on the “Under review” button, to see your quote status… In my case, it took about 5 minutes for the review to pass, and be able to checkout and pay for the order…

PCB order under review

Once the review has passed, you will see a pending payment,

Payment Pending

You may now click on the “Proceed to Payment” option

Add your shipping address, and choose your payment option.

At this moment in time, only two payment options are supported, Paypal ( as well as Debit and Credit cards) and Direct Bank Transfer. I believe more options will be made available in future..
Checkout with Paypal

In my case, I chose Paypal and paid by Debit card.

Enter your card details
After Payment.

After payment was made successfully, you can also check on the status of your order…

Review your order status

You can also review your order at any stage before or after payment, as well as get progress reports of the manufacturing process.

PCB Order Status.

In conclusion, I would like to say that it was quite easy to order and make payment. The Website is easy to use, and everything is clear and easy to understand. The PCB was well manufactured and seems to be quite good quality

IO Shield for LoRa Base Module

INPUT And Monitor Shield for LoRa Base Module

Introduction

This is a straightforward project compared to my usual PCB projects. It is one of a series of designs towards completing my LoRa monitoring system, that I plan to use on the farm to monitor various areas, such as intrusion detection, battery levels etc.

The shield was designed to fit on top of the first LoRa Base Module. It was designed to allow easy, neat connections to Infrared Beam sensors, XYC-WB-DC Motion Detector, as well as to monitor the battery levels at the Solar power inverter (the farm is completely off-grid).

The Motion Sensor provides a +3v signal that goes high on motion detection, while the Infrared Beam Sensor provides a relay contact that can be used to provide a similar voltage signal. As I prefer to use pull-up logic on my inputs, I decided to implement a simple transistor circuit where the input will switch the base of the transistor, which in turn will pull the input to signal ground when switched on. This circuit uses the S8050 transistor, with the base pulled down to signal ground via a 10k resistor to prevent floating, and a current limiting resistor of 1k to 1k8 on the base. The collector, as well as the D7 and D8 GPIO pins on the LoRa Base Module, is pulled High to Vcc5v via a 10k resistor.

Voltage monitoring is done with the ADC on the LoRa Base Module, with each of the 4 battery levels ( 12v, 24v,36v, and 56v) being connected to the relevant ADC channel via a resister-divider network to lower the respective voltage to a level between 0 and 5v. ( This was done as the ADC on the ATMEGA328p can only handle a maximum voltage of 5.0v )

The resistors were chosen to give a slightly bigger input voltage range, to accommodate for fluctuations from the solar charger ( It can sometimes go up to 65v on a very bright sunny day ). I decided to not add any current limiting resistors directly onto the PCB, as they are definitely going to be bulky. They will instead be attached externally, to suitable heatsinks, etc…

As this PBC is still in the prototype stage, and my LoRa Monitoring device will definitely go through quite a few modifications in future, I provided access to all unused GPIO pins via separate headers on the shield. Most notably the SPI Header, used for programming the ATMEGA328P MCU, or connecting other SPI devices ( I am working on a CAN bus addon for the device, to save on the number of physical radio nodes that needs to be installed), The UART Header, as well as I2C, A6, A7 and additional Digital IO Pins (D3~, D4, D5~).

In the photo above you will notice an additional header on the UART pins, This was added to assist me with debugging on the logic analyser, as I had a slight issue with waking up the ATMEGA328P, and getting it to send events via LoRa. It would wake up, print status messages through the UART, but never do the actual LoRa part! That has now been fixed, and the header removed…

The schematic diagram for the shield is below. As you will see, it is very uncomplicated indeed.

Software and Libraries

The LoRa Base Module has been designed to use the LoRa Library from Sandeep Mistry. Further versions of this PCB will also directly support the RadioLib Library from JGromes.

A reminder :

The RA-02 Module (SX1278) connections to the ATMEGA328p is as follows:

NSS to D10 (CE)

MOSI to D11 (MOSI)

MISO to D12 (MISO)

SCK to D13 (SCK)

RESET to D9

DIO0 to D2 ( We need a hardware Interrupt pin ).

DIO1 to DIO5 was not broken out on the current version of the LoRa Base Module

There is also no direct access to pins D10, D9 and D2 either on the LoRa Base Module or on the Input and Monitor Shield.

If you do decide to hack the device and add access to any of the non broken out pins, please remember to use a logic level converter between the ATMEGA328 and the SX1278, as they operate at different voltages, and the SX1278 is not 5v tolerant on any of the IO Pins!

You can order this shield from PCBWay by clicking here

This PCB was manufactured at PCBWAY. The Gerber files and BOM, as well as all the schematics, will soon be available as a shared project on their website. If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…
1) Click on this link
2) Create an account if you have not already got one of your own.
If you use the link above, you will also instantly receive a $5USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
3) Once you have gone to their website, and created an account, or login with your existing account,

4) Click on PCB Instant Quote

5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.