Over-the-air updates

[philputman]

The page in PyCubed Resources for over-the-air updates says coming soon... Is there any information available? We're preparing to work on that and would like to avoid repeating work unnecessarily.

[maholli]

hi @philputman

In my mind, over-the-air (OTA) updates fall into two categories:

1. OTA software updates (changing the python flight software)
2. OTA firmware updates (changing the low-level firmware)

A mechanism for OTA software updates is introduced near the end of the PyCubed Beep-Sat Advanced example. OTA software demos are further expanded in the Beep-Sat "Advanced-2" example I started putting together (note that link is a branch of the beep-sat example repo). "Advanced-2" is still a bit rough around the edges, but it demonstrates deep sleep functionality via the alarm module, which enables things like wake-from-radio (aka "hot start") and improved low battery behavior. It also provides a working example of multi-message OTA command mode which allows you to chain OTA commands together by setting a flag within the packet. I've successfully used these OTA techniques in prior on-orbit missions and plan to do so in the future as well.

As for OTA firmware updates, I had a working proof of concept as of a year or so ago. However, this requires significant changes to the underlying CircuitPython and MicroPython framework and my quick implementation is likely indecipherable for anyone but me. Compounded by the ongoing chip shortage and inability to supply folks with PyCubed boards, chose not to develop this any further.

Hopefully this illustrates where things stand. If you end up working on your own OTA firmware implementation, please report back with a link to the repo! I know myself and others would love to see it.

[polygnomial]

Curious about your OTA firmware update proof of concept—did you implement dual bank support on SAMD51? I half heartedly wandered around that part of the data sheet for an hour or so and then decided to focus on OTA software updates instead.

[polygnomial]

I am working on OTA software updates for updating any file (except boot.py). I will share my code once I get it working how I'd like and have tested it to some degree.

My general strategy is:

1. Automated test software runs on an engineering model on the ground and manual data/log review on the ground before uploading any code
2. Make a complete complete backup copy of all source files in MRAM
3. Leverage supervisor.set_next_code_file for the actual software update configured to try the new main file only once. Upon reboot, revision happens automatically. (Might change this to increment a counter so that PyCubed makes some number of try's with the new code before reverting).
4. Enable the (software) watchdog timer from CircuitPython, and make a feeder task for it. This way, in case I accidentally introduce some code that hangs in an edge case that wasn't caught in ground testing, it will reboot itself. This is a separate watchdog timer from the. This task will only be scheduled when PyCubed is attempting a software update.
5. Additionally, increment an MRAM timer within the watchdog feeder task and check for a "verification" flag in MRAM that is set by a regular OTA command from the ground.