Updating an Arduino and a PI with single git push

Micro-controllers are simple boards that can run C/C++ programs. Owing to this simplicity they are easy to use and amazingly power efficient conversely this simplicity makes them incompatible with resin.io :( This is because the resin.io service relies on moving Linux containers around and these boards can't run Linux. However a couple weeks ago one of our users explained how he was using resin to update his Raspberry pi and an attached Arduino.

I've expanded his explanation slightly to create this guide an Arduino update mechanism within the resin.io ecosystem.

The basic workflows is this:

• Connect your Arduino to a resin device via USB-serial.
• Change some Arduino code.
• Push your your project to resin.io. This uses a Makefile to build your Arduino binary(from blink.ino) on our builders and ship everything to the resin device in container.
• When the container lands on the device check if there is a difference between the new version of Arduino code and previous version (which is stored in /data to persist through resin updates)
• If there is a difference raise a flag to signal the uploading of the binary to the Arduino via the serial cable.
• Arduino is updated with new code (a longer delay in the blink sequence).

Let's take a look at some code

Because the Makefile and resin.io abstract all of the tricky stuff the logic is actually very simple.

The basis for all resin projects is a Dockerfile so lets start there. Firstly we need to install some native dependencies.

# DockerfileRUN apt-get update && apt-get install -y --no-install-recommends \      arduino \    g++ \    gcc \    usbutils \    make

Next we trigger a build of our Ardiuno firmware from our Arduino source file using this "all-in-one" Makefile. It allows you to pass build configurations via environment variables. As you can see we are building for the leonardo board. Full documentation on the make file can be found here.

# Dockerfile# build the Arduino binaryWORKDIR /appENV ARDUINODIR /usr/share/arduino  ENV BOARD leonardoRUN cd blink && make 

Once the container hits the device we'll need to run a script to compare the code in blink.ino against the previous version. We declare our entry point like so:

# run start.sh when the container startsCMD ["bash","start.sh"] 

In start.sh we have a flag PROGRAMMER which indicates whether there is an update for our Arduino. If the flag is raised we run make upload which uploads the binary via serial connection. We then store our new blink.ino in /data. This is important because resin.io treats /data similar to Docker sub-volumes, in that its contents survive container updates, which is of coarse crucial to making the comparison between new and old code.

# start.shdiff /app/blink/blink.ino /data/blink.ino || PROGRAMMER=1  if [ "${PROGRAMMER:-}" == "1" ]; then    echo $PROGRAMMER  pushd /app/blink  make upload && cp blink.ino /data/  popdfi 

You can view the write progress from the resin logs.

* *Note: I've stripped out a few extraneous details. **

12.01.16 13:04:58 [+0000] Connecting to programmer: .  12.01.16 13:04:58 [+0000] Programmer supports the following devices:  12.01.16 13:04:58 [+0000] Device code: 0x44  12.01.16 13:04:59 [+0000] avrdude: AVR device initialized and ready to accept instructions  12.01.16 13:04:59 [+0000] Reading | | 0% 0.00s Reading | ################################################## | 100% 0.01s  12.01.16 13:04:59 [+0000] avrdude: Device signature = 0x1e9587  12.01.16 13:04:59 [+0000] avrdude: reading input file "blink.hex"  12.01.16 13:04:59 [+0000] avrdude: writing flash (4756 bytes):  12.01.16 13:04:59 [+0000] Writing || ################################################## | 100% 0.59s  12.01.16 13:04:59 [+0000] avrdude: 4756 bytes of flash written  12.01.16 13:04:59 [+0000] avrdude done. Thank you. 

And there you have it. Updating an Arduino using resin.io. You can find all the code here.

Theres a ton of interesting use cases to apply this to for instance using the Arduino as an ADC like Emonpi has done. Let us know where you take this. Programming the Arduino via bluetooth would be a great fork ;)

If you have any questions, the team will be hanging out in our gitter room.

Note

If you want to pin the programmer to specific port e.g /dev/ttyACM0 then you'd add another environment variable, like so: ENV SERIALDEV /dev/ttyACM0.