CAN Log Library

Overview

The CAN Log library provides a log backend for logging messages over a CAN bus.

It is enabled by default for the ARDEP boards.

Configuration

To enable the CAN Log library, setup logging in your project and enable the CAN log backend by adding the following to your prj.conf:

CONFIG_CAN=y
CONFIG_LOG=y

CONFIG_CAN_LOG=y
CONFIG_CAN_LOG_ID=0x100

# Setup the preferred log mode and processing strategy
CONFIG_LOG_MODE_DEFERRED=y
CONFIG_LOG_PROCESS_THREAD=y

If your project does not start CAN itself, you also need to autostart it by adding CONFIG_CAN_LOG_AUTOSTART_BUS=y which will start CAN on the default bus during initialization.

Dynamic CAN ID

For the ardep boards, the can id is provided by the Gearshift Address Providers module by default.

You can disable this module by setting CONFIG_GEARSHIFT_CAN_LOG_ADDRESS_PROVIDER=n

Custom Address Provider

If the gearshift can log address provider is disabled, you can provide your own CAN log ID by setting CONFIG_CAN_LOG_ADDRESS_PROVIDER_EXTERNAL=y and implementing the can_log_get_id() function in your code:

#include <ardep/can_log.h>

uint16_t can_log_get_id() {
    // Return dynamically determined CAN ID
    // For example, read from hardware pins or configuration
    return my_calculated_id;
}

When this function is implemented, it overrides the CONFIG_CAN_LOG_ID configuration value. The function is called during CAN log initialization to determine the CAN ID to use for log messages.

This is particularly useful in multi-node systems where each node needs a unique logging ID, or when the ID needs to be determined based on external factors like gearshift position or other methods of device addressing.

Receiving Logs

The CAN frames that are sent via the ID configured with CONFIG_CAN_LOG_ID contain the raw log message data, 8 bytes per frame maximum. To receive and decode these log messages, you can use the provided can_log_receiver.py script located in scripts/ or use the west ardep can-log-receiver command. There you can setup your CAN interface via -i can0 and the CAN ID to listen to via -id.