Update Sensor Parameters over CAN Bus

[SamrutGadde]

Currently, the sensor boards require a re-flash whenever changes are made to their CAN ID, and sensor frequency rates. This is quite annoying to do, and wastes a lot of time. Instead, it would be nice to define a communication protocol where the board could look for specific messages on the CAN bus and updates variables in their code dynamically from the values sent!

I would like this to be independent of the sensor boards themselves, and act as a library that any of our CAN-enabled boards can use to do parameter updates.

Requirements:

• A way to update a specific memory location on a board
  • This is defined by the board itself - the board should expose certain values that this library can update
• Should be a full message protocol, containing request and response frames, which include success and error cases.
  • Think about how different boards can use the same CAN ID to listen for updates
• The specific details of the boards should be abstracted away - the library should contain the ability to expose updatable values and it should be clear from the protocol how those values can be updated.

Think about how this message protocol should look. Once you come up with an initial solution, feel free to bring the ideas to others to get feedback.

Once you get a working design, create a new repo to add this library into, then once it works, create a pull request here to close this issue.

[SamrutGadde]

Come up with an initial solution by the end of the workday, 09/27

[kjn01]

Here's our initial design:

Exposed fields:

• CAN ID
• Frequency rates

CAN Frame format:

• Has specific CAN ID for reflashing
• Data:
  • 0: Device ID
  • 1: Field we want to change (CAN ID, sensor frequency rate), same as offset from start of buffer
  • 2-5: New data to set the field to (32 bits)
  • 6-7: Extra data (unused for now)

Each device has flag for ‘if we can write to this device’ and ‘device id’

Each device has a set list of fields that can be changed

When board is first turned on or car is turned on request flash data (return device id, or error if writing flag is false) and store in a list within the library

Separate file (text or something) has a mapping of all data of all devices you can update to the size

Workflow:

1. List all available devices in library, each device will return id or CAN message with error if write flag is false
2. List all field locations for each device (each device has a specific buffer)
3. To set field in a specific device (device id), device with device id locates field specified in byte 1 with list from step 2 and set to data from bytes 2-5:
   a. Device sends new CAN message saying operation is done

[SamrutGadde]

Looks good to me! A question though: Will the device ID be the device's CAN ID, or something else? I'm thinking about how these commands will get added to the DBC for documentation.

[SamrutGadde]

Looks good to me! A question though: Will the device ID be the device's CAN ID, or something else? I'm thinking about how these commands will get added to the DBC for documentation.

Discussed, think this will be best with a hard-coded device ID on each board that uses the library, since CAN IDs are subject to change.