cone10
Is there a better way to send tweaks to elixir source to RPi than burning firmware?
I’m new to both Elixir and RPi, so forgive me if I am missing something totally obvious.
After burning the firmware on the SD card, say I want to simply tweak one source file. Is there a simple way to do it? I don’t want to re-burn the SD card … that’s so 1980’s!
How does one do dynamic deployment at dev time?
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axelson
Welcome to the forum 
!
Assuming you created your project with nerves.new then nerves_ssh should be enabled by default: GitHub - nerves-project/nerves_ssh: Nerves SSH support · GitHub
The gist of it is to run mix firmware, then mix firmware.push (possibly providing the nerve’s device ip address). So that will upload the new firmware to the device and then it will automatically restart. If want to revert to the previous firmware you can ssh to the device and run Nerves.Runtime.revert.
elcritch
You’ll probably use both methods.
Nerves builds a “firmware” in that it contains everything to run the RPi, including the Linux kernel and your elixir code. Assuming you’re using Nerves for this. That firmware image is readonly.
However, since Elixir is an interpreted language you can upload code into a running Elixir VM (called the BEAM) via the Elixir shell (basically IEx). You can paste a module and it’ll then recompile the code and run it. Super handy for trying out i2c devices, html tweaks. It only takes a few seconds usually.
The copy/paste method gets tedious for big changes or lots of modules. Also any changes will be lost on reboot since it’s read-only. So you’ll want to make an updated firmware and push it regularly. It’s a bit slower to build the firmware since it’s rebuilding the entire rpi system, but not too bad (only a minute or two).
I tend too try several small changes via ssh and then upload a new firmware once I’m done. It’s sort of like connecting to a running docker container, tweaking code, and then building a new docker container with the changes and re-booting the container instance.
Sebb
Nerves is not meant for “compile-edit-run-debug” (on the hardware).
Build the system on your workstation (write tests) and only occasionally do an integration test on the hardware.
Even if you are heavily using hardware peripherals, its normally not too hard to write tests.
If you don’t want to / can’t do that, you could just not use nerves for development and set up sth like this:
This could also be worth a look:
https://github.com/nerves-project/nerves/blob/main/docs/Experimental%20Features.md#firmware-patches
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