pi3hat firmware and python release 2021-11-29

There’s an updated release out for the mjbots pi3hat which features a useful bug fix and a minor feature.

First, the configuration of automatic retransmission was broken in several ways. The symptoms for previous versions would be that any attempt to change the CAN configuration for a bus would result in all channels attached to that controller having auto-retransmit turned off. Since it was by default on, that would typically result in a decrease in transmission reliability, and in some particular cases with arbitration conflicts, could result in frequent packet loss. Fixing this requires updating both the firmware on the device and the C++ and python libraries. Fortunately, this would only come up if you were communicating with non-moteus devices using the pi3hat, which likely isn’t that common.

Upgrading the firmware of existing pi3hats is not trivial, since it requires use of the external stm32 programmer and an openocd version that is not yet packaged in any major Linux distribution.

Second, the python packages have been updated to support the newly released Raspberry Pi OS “bullseye” 11.0 out of the box.