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.

VC-01 and VC-02 Offline Voice Module

In a recent article, I took a look at the new VC-01 and VC-02 Voice offline voice modules from AI-Thinker. I mentioned that I was working on a very simple prototype PCB to do some more tests, as well as make practical use of the module in real life.

In this very short post, I will show off the initial prototype that I came up with.
While I have to admit that it is still in an extremely basic stage, It is already definitely useful.

Part of the reason for this is that there is not a lot of information available on the VC-01 and VC-02 at this stage, as well as the fact that more exotic features like I2C and SPI are still not accessible in the current firmware. I thus had to work with what was available, as well as take into consideration what will work with the standard factory firmware as well.

The prototype carrier PCB will thus only have two optically isolated relays and their supporting circuitry. I intend to actually use the PCB in my EE LAb area to control some of the lights in the area.

The Schematic

The schematic shows the relay control circuitry, comprising of my standard optic isolator-based relay driver, as well as headers to accept the VC-01 or VC-02 offline voice module kit PCB.

Testing the PCB

The PCB was tested using the standard factory firmware, as well as my custom firmware, kindly provided by AI-Thinker. Below is a short video of that in action. Please note that the relays was not yet connected to any external devices at this stage.

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.

True OFFLINE Voice Assistant

Most of us are familiar with voice assistants these days; Google Assistant, Siri and Alexa are obviously the most well-known of these. They all share a common problem though: They are online, and can thus secretly record everything you say around them, for later use by their respective owners [ The Companies that created them ]. Having a true offline voice assistant can thus seem like the holy grail for privacy and security-minded people.

Introducing VC-01/VC-02

I was recently contacted by AI-Thinker and asked if I was interested to play with a new product of theirs, an offline voice module. I immediately jumped at the opportunity, as this was something that I wanted to get my hands on for a long time, providing it works of course…

AI-Thinker’s offline voice module is available in two models, the VC-01 and the VC-02.

My Sales Representative (Kat ) sent me both models, in a kit format, complete with speaker and microphone. The kit PCB also provides a USB port with a ch340 chip, as well as two push buttons (reset and wake-up) as well as 3 built-in LEDs ( White, Orange and Blue ).

These light up with the factory firmware, depending on what commands are issued to the device…

Let us take a look at how the factory firmware works; Thank you to Kat from Ai-Thinker for uploading the video, and sending the link to me 🙂

As we can see in the video above, the module seems to work very well… The question now arises if it can be customised to do what we want it to…

Custom Firmware – Do-able, but with a few caveats

Information in English on this module is very sparse. This is due to it being very new, and with AI-Thinker focusing most of their efforts for this module on the Chinese market for the time being. Which makes sense in one way, but also doesn’t in another.

After spending quite a bit of time trying to get information, my Sales Rep eventually gave me access to an online configuration utility, now be warned:
This is not for the faint of heart. The entire interface is in Chinese ( They are working on an English version, with time-to-completion between one (1) to four(4) weeks from starting the project. I can however not give any accurate dates at this stage, but was told that this development is underway).

Being no stranger to different languages, I thought to use google translate to translate the website. No, that didn’t work. Google refuses or the Chinese Website doesn’t allow it to? No answer as of yet. Any readers who do know any reasons for this, please comment below.

I was sort of successful in manually copy pasting line by line into google translate and got some translation back, but it was not very useful.

My next point to try was asking AI-Thinker to generate some firmware with the web tool. They gladly did that, and that works great. It is however not feasible in the long term to go that route every time.

This was possible because the AI-Thinker engineers, using the firmware development software, currently only available in Chinese, can set custom wake words and train voice commands with a 95% accuracy rate, before generating firmware and flashing it onto the respective module.


Write your own, someone will obviously say, and that was my next attempt. There is an API, and source code on GitHub, as well as Gitee ( The Chinese version of GitHub) The two sources are however not synced, and I was still not successful in getting anything useful from Gitee, once again due to a language issue, as well as the fact that some of the sources depend on 32bit dependencies for Ubuntu, whereas I am running a 64bit version… I did try it though, and can not report any success on that venture at all.

Once again, I will advice us all to wait for AI-Thinker to release an English version of the SDK and API for us all to use, which I am sure they will do at some stage in the near future.

See the video below of my custom firmware, once again demonstrated by Kat from AI-Thinker

Custom Firmware – Test 01

As we can see, it once again performs well, with a few issues, but quite acceptable…

Hardware access to the real world

As we have just seen in the video, there is also hardware access via pins, to the real world. There are however a few issues there as well…

Hardware pins are limited.
I2C and SPI, although advertised, are apparently not yet supported in any of the current firmware – Someone with information, please comment…

While there are 2 I2C interfaces, they can not be used at the same time
Information on the module

PCB Prototype – Of my own design

As a proof of concept, I have decided to design a quick prototype with relays to use as a more detailed test. I will update information on that soon…

My Conclusion

I definitely see potential here. This is a product which can be quite useful in the future, providing that the following is done:

Proper detailed documentation is provided in English as well as Chinese
API and SDK access is made available in English as well as Chinese
Firmware be updated to make all features available

Having said all of that, I do understand that development, and especially R&D do take a lot of time. Translating documents accurately does too.

I want to congratulate AI-Thinker on producing a very well-made unit, that will definitely bring the dream of a totally offline voice assistant a little bit closer to being a reality.

Voice recognition with my bastard South-African/British English Accent, heavily influenced by Afrikaans, went extremely well, even with the factory firmware.
I do thus not think anybody that can speak passable English will have a problem using the unit.


ESP-12E I2C Base Card

As a follow-up on the ESP-12E Card, today we will look at the prototype base card that this was designed to slot into – The ESP-12E I2c Base Card.

Initial Features ( To be expanded in future versions )

4 x 40Pin Expansion slots, with access to 12v, 3.3v and Gnd on each slot.
2 x “IRQ” pins per slot ( serviced by a single PCF8574 )
I2C bus access on each slot (3.3v )
UART Header
Reset and Flash Header
GPIO Header ( Direct access to the ESP-12E GPIO Pins )
Analog Input Header (a Single input – A0, as per ESP-12E limitation)
Buck Converter Power Supply Module, capable of up to 2A of current

ESP-12E I2C Base Card – Top view

The Schematic

Schematic

The PCB – some pictures

ESP 12-E Card with Base Board

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.

ESP-12E Card

A few months ago, I started working on an MCU Card design, which borrows from the idea of a standard desktop PC, in which there are a main-board, MCU and expansion slots, to add and remove peripherals as needed quickly.

The ESP-12E Card is a continuation of that project, with the ultimate goal to have a universal “main-board” that can accept various MCUs and standardised “expansion modules” that perform a specific task.

ESP-12E Card
ESP-12E Card

The PCB

The ESP-12E Card contains the bare minimum components to allow the chip to function. There are no power regulators or USB-to-TTL converters onboard. Code is flashed via an external USB-to-TTL converter, with Flash and Reset buttons on the actual PCB, or available in the 2×20 Pin female header at the bottom of the card.

Most of the GPIO is also broken out to the 2×20 pin header, with the exception of the 6 GPIO that is usually connected to the internal Flash on the ESP-12E module.

I have made provision for enough power and ground pins on the header as well.

As far as GPIO is concerned, They have been grouped together by function, as much as possible at least, to make interfacing with the base-board as easy as possible.

The Schematic

ESP-12E Card Schematic

The schematic is not complicated. It is a standard ESP-8266 configuration, with all non-essential components removed.

The “base-board” ( a sneak preview )

Sneak preview of the Base Card

In a future article, I will tell you more about this ( for the time being limited to I2C ) base card. [ a quick explanation: When I mean limited to I2C, it relates to the fact that at the moment, the base card, ( a prototype ) can only communicate back to the MCU via I2C protocol from each of the expansion slots, as well as via two dedicated IRQ lines from each slot ]Power is supplied via a small SMPS module.

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.

ESP32-S Card Module

ESP32-S Card Module

What is this?

This project is the result of a lot of prototyping, using different MCUs and wanting to find a way to get a standard interface to all the devices.

The idea is to eventually create similar card-type MCU breakout boards, with similar pins in the same position on the 2x20p breakout header,

for example, power, i2c bus, reset and flash will always be in the same position on the female header…

Step 2 from here on would be to design a baseboard, that is capable of providing power, as well as access to the various GPIO pins. I am thinking along the way of a PC motherboard style interface, with “slots” at regular intervals. These “slots” will have access to the SPI, and I2C bus, as well as various other GPIO.

Step 3 would be a series of commonly used input and output “cards” that will plug into the “slots”…

If successful, I plan to design various MCU cards, with various different processors, with the obvious criteria that they are 3v powered.

This could result in a very flexible development platform, where it is possible to reuse the base-board and IO “cards” with any one of the various MCU “cards”.

The Schematic

As seen on the schematic, almost all of the ESP32-S’s pins are broken out, with the exception of those used for internal flash. Reset and Flash circuitry is provided on the PCB, as well as on the 2x20pin female header.

It is worth noting that I did not include any UART to USB circuitry on the card. Flashing should be performed with an external USB-to-UART converter. It will however be included in the base-board.

There is also no power supply circuitry onboard. This was also intentional, as the card is intended to be powered from the base-board. It is however perfectly acceptable to power only the card from a suitable 3.3v DC power supply unit through the 3v and gnd pins on the 2x20pin header.

Where can I get my own version of this module?

This module will be exclusively available from PCBWay for the foreseeable future. Click on this link to order your own, and help support a great company that produces very high-quality PCBs for a very affordable price.

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.

CAN-to-LoRa gateway using RA-02, MCP2515 and ATMEGA328P

ATMEGA328P Module with integrated LoRa and CAN-BUS

INTRODUCTION

In my quest to perfect my LoRa telemetry system, I have gone through quite a few prototypes by this time. This post will focus on the next node design. Due to the fact that the area where I will deploy the system is quite large, but with roughly square boundary fence-lines, I decided to try and reduce the number of LoRa Radio nodes needed to cover the entire area. This opened up the opportunity to utilise CAN-BUS to attach sensor-only nodes to a Radio node and have them report status on exception as well as on requests from the radio node.

The device will thus function as a LoRa-to-CAN-BUS Gateway, with some local automation to control the transmission of data to the master station. This concept can also be adapted for use in other areas, such as home -automation, or an industrial setting.

At the heart of the device, I have stuck with the versatile ATMEGA328P, which, current chip shortages excluded, and current high prices excluded, are a very inexpensive chip, with lots of well-tested libraries, and a relatively low learning curve, largely due to its very wide use in the Arduino ecosystem.

The LoRa component is handled by the RA-02 or even RA-01H module, from AI-Tinker (not sponsored). This device, as we have seen in the previous prototypes, requires the use of logic level converters, due to the fact that it only accepts 3.3v logic levels. While I could get rid of those if I powered the ATMEGA328P from 3.3v, it would give rise to two problems, of which one will still force the use of level converters…

I chose to run the ATMEGA328P at 16Mhz, which basically forces me to use 5v to power the chip. The second reason is not so obvious unless you read a few datasheets very thoroughly…

The CAN-Bus component is handled by the MCP2515 Standalone SPI-to-CAN Controller, as well as the TJA1050 CAN Bus transceiver.

This is where things get interesting… The MCP2515 can operate on 3.3v, but the TJA1050 is a 5v only device. I could thus in theory use logic level converters only between the MCP2515 and the TJA1050, while running the rest of the circuit on 3.3v…

Given that I would rather run the ATMEGA328P on 16Mhz, as well as the fact that my LoRa Radio Module circuit, with its logic level converter circuitry, works extremely well, I decided not to change that, and keep the CAN Bus running at 5v all the way through, as I would still have to use a 5v regulator on the PCB anyway just for that purpose.

IO connections for LoRa and CAN BUS modules

You can order this PCB directly from PCBWay, by clicking here

Both of the two integrated components ( Lora and CAN ) are SPI devices. This means that they share common SCK, MISO and MOSI lines ( provided on the ATMEGA328P by pins D13, D12 and D11 respectively. The individual SPI device is then further selected for operation by the use of a CE pin, one unique pin per device, which is pulled low by the MCU to indicate to the device that it should pay attention to the data being transmitted on the SPI bus…

Both LoRa and CAN makes use of other pins as well, LoRa needs a Reset pin, connected to D9, a CS/CE Pin on D10 as well as a hardware interrupt pin, connected to D2. ( Note that this is for use with Sandeep Mistry’s LoRa Library. The Radiolib library would require an additional pin, usually connected to DIO1 on the LoRa module. The device does not provide access to those pins in its current layout, so you can only use it with the Sandeep Mistry library, for now at least… )

The CAN module uses a CE/CS pin at D4, with an IRQ pin on D6, which, although not a hardware interrupt pin, does have PCINT functionality.

Pins D10, D9 and D2 are not broken out for user access. although I decided to give access to D4 and D6, as well as the SPI bus, D11, D12, D13, to allow interfacing with logic analysers, or adding other SPI devices to the bus…

This brings us to a very interesting point… Does the two SPI devices actually play nice together? and what do I mean by “playing nice together”?

To answer that question, we are forced to first look at a bit of theory, as well as understand the fundamental differences between SPI and I2C…

The Difference between SPI and I2C

Most of us will be quite familiar with I2C, as it is a very common protocol used to connect sensors to a microcontroller. It consists of only two IO lines, SDA for data, and SCL for the clock. Each device on the bus has its own built-in address, like in the case of a PCF8574 IO expander, this address can be selectable between 0x20h and 0x27h. All of the devices share these common data lines, and will only respond when specifically addressed by the master controller… Unless you accidentally put two devices with the same address on the same bus, (if that would even work), there is no way that the wrong device would respond to any request for data…

SPI on the other hand, operates on a completely different principle, making it quite a few times faster than I2c, with data being simultaneously sent and received by the active device… SPI is also known as a four-wire protocol. Each device has a minimum of 4 data lines, namely SCK ( clock), MOSI ( for data transmitted FROM the Master TO the slave device ), MISO ( for data transmitted TO the master FROM the slave device) and a CE or CS ( Chip select ) pin.

SCK, MISO and MOSI are COMMON to all devices, meaning it is shared between all of them. CE/CS is a unique pin for EACH device, meaning that if you had four SPI devices on a bus, you would have to have four individual CE/CS pins!

A device will, or rather should only respond to data on the SPI-BUS IF the master pulls its respective CE/CS pin LOW. It should now very quickly become clear to you that this can become a very very complex mess, very quickly.

Let us take a very good example. the ST7789 SPI display module, has a cheap version, commonly sold on Ali-express, as we ll as other online stores. This particular module, I assume in a bid to make it easier to use, has the CE/CS pin internally pulled down to ground by default… So what about that, you may ask? What is wrong with that, as it saves you an IO pin?

It is in fact very wrong, a fact that you will very quickly discover if you ever tried using one of those displays on an SPI bus together with other SPI devices… Nothing will work, or only the display will work ( if you are lucky)

But why?

Pulling CE/CS LOW, signals to the chip that it should respond to instructions on the common SCK, MISO and MOSI lines. having the pin internally pulled LOW, thus forces that chip to always respond, even when it should not. Thus contaminating the entire SPI-BUS with garbage…

The answer to the question

After that very long-winded explanation, which is still extremely basic, it is time that we get back to our original question:

Does the Sx127x ( RA-02 ) Module and the MCP2515 Can Controller play nice on the same bus? The answer is not straightforward, as it comes down to which libraries you use…

Remember that the library must pull down the CE/CS pin of the device that it wants to communicate with. Some libraries wrongly assume that they are the only ones in use, and ignores the simple fact, that they should release the CE/CS pin AFTER EVERY transaction, to free up the bus for other devices to use it as well…

After extensive testing, I can however say that Sandeep Mistry’s LoRa Library, as well as the mcp_can library, does indeed play nice together. These two libraries do not keep the individual CE/CS pins pulled LOW, and allows the spi bus to be shared.

This is not the case with the ST7789 Module discussed above, where the hardware actually pulls the pin ow the entire time…

Taking a closer look at the PCB

Let us take a closer look at the PCB. The Ra-02 Module ( LoRa ) dominates most of the left-hand side of the PCB, with the ATMEGA328P on its right. The RA-02 is surrounded by the level converters, using the BSS138 N-Channel Mosfet, and 10k resistors (Q1 to Q6, R1, R2, R3, R4, R5, R6, R8, R9, R10, R11, R12, R13)

C1 and C2 are bypass capacitors for the Ra-02 module

In the bottom left corner, we have a hardware reset button, to reset the ATMEGA328P, with a yellow jumper (H1) next to it. This jumper controls the 120ohm ballast resistor (R17) for the CAN bus. Removing the jumper will remove the ballast. Directly below that is the CAN connecter, marked as U5, with CH as CAN-H, and CL as CAN-L ports.

U3 and U4, together with R18, R19, X2, C16, C17 make up the CAN components on the PCB. Decoupling is provided by C6, C7, C8 as well as C9 and C12 ( Includes the ATMEGA328P’s decoupling as well )

An ICSP programming header is provided above U1 ( ATMEGA328P) for use with USPASP, AVRASP or Arduino as ISP and similar.

No USB to serial converter is provided on the board, Serial upload is possible is loaded with an Arduino bootloader for the Arduino NANO ( to make use of all the analog inputs). RxD, TxD and DTR pins are broken out on opposite sides of the PCB, as well as access to 3.3v, 5v and GND pins.

A DC power socket is provided. it can accept up to 12v DC, although I would recommend not to go over 7.2 volts, to not stress the LDO regulators, at the back of the PCB ( LDO1, and LDO2) too much.

You can order this PCB directly from PCBWay, by Clicking here

in the picture above, I have connected a USB-to Serial converter, as well as CAN-BUS to the device.

Schematic Diagram

The detailed schematic diagrams are provided below:

Sheet 1 (above) takes care of the ATMEGA328p and it supporting circuitry, as well as the power supply via LDO regulators.

Sheet 2 (below) takes care of the Logic Level converters, RA-02 (Sx1278) LoRa Module, and CAN-BUS controller and transceiver circuitry.

Software and Firmware

In order to test this module, I made use of the mcp_can library by Cory J Fowler, for the CAN-Bus part,

as well as Arduino-LoRa by Sandeep Mistry

A combined example utilising both LoRa and CAN at the same time, will be released with the next part of the project, namely the CAN-Relay Module

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.