Research CAN Filtering

[Koloss0]

🗒️ Task Description

Summary
Research whether CAN filtering at the hardware level would be applicable to our current CAN protocol.

Details
You may have noticed this fancy-looking struct in the main file for the CAN Wrapper Module.

This struct defines a bunch of settings for CAN filtering, which refers to the filtering of messages received on the CAN bus based on the value of the standard ID (also known as the StdID).

For this task, do some research into what all those fancy values mean, and figure out if we can use them to our advantage and avoid processing messages we don't care about. To do this, you will need an intimate understanding of how CAN works, how the HAL API functions, and how our custom protocol (it sits on top of CAN) works.

✅ Completion Criteria

• Identified how the HAL API works. That is, what all the values mean
• Determined if there is a way to configure the struct to filter out messages that aren't relevant to the subsystem receiving them.
• Defined a clear plan on what changes would need to be made to support the filtering behaviour, without disrupting the functionality of the system.

🚧 Notes / References

Here are some links that might aid your research:

• Page 123 of the HAL STM32L4 API documents the CAN filtering struct fairly well.
• CAN Bus on Wikipedia explains CAN and how it works.
• This document explains our custom CAN protocol on a high level.
• This document explains how ACKs work, which are an essential component of our protocol.