ESP32 Forum

we are using the can interface, idf 3.3.5 release version.

We have a seperate recovery task to get CAN alerts ant to recover from BUS_OFF. Basically we followed the recovery example, contained in the idf.

we are get the alerts properly (eg if we shorten the bus for a short moment), also the bus recovers propperly from bus of by calling the function can_initiate_recovery().

Our problem is that the event "CAN_ALERT_BUS_ERROR" is only working until the first occurence of a bus recovery. After the first recovery, the system does not report alerts like CAN_ALERT_BUS_ERROR anymore.

Reading the counters by using can_get_status_info() sows the same: info.bus_error_count counts up in case of a bus error, but after a bus-recover the counter of bus_error_count stays at its last value before the recovery happened.

A reconfiguring of the needed alerts after a bus recovery does not help.

What is wrong? Why stays the bus error counter at its position when a bus off occures and the bus recovers (and stays there till a complete restart?)

thanks for your help.




Juergen





Code snippet:

void can_recovery_task(void *arg)
{
ESP_LOGI(tag, "Starting CAN recovery task");

while(1)
{
uint32_t alerts=0;
can_read_alerts(&alerts, portMAX_DELAY);
ESP_LOGI(tag, "---Alert Read: -- : %04x", alerts);

if (alerts & CAN_ALERT_ABOVE_ERR_WARN)
{
ESP_LOGI(tag, "Surpassed Error Warning Limit");
}

if (alerts & CAN_ALERT_ERR_PASS)
{
ESP_LOGI(tag, "Entered Error Passive state");
}

if (alerts & CAN_ALERT_ERR_ACTIVE)
{
ESP_LOGI(tag, "Entered Can Error Active");
}

if (alerts & CAN_ALERT_BUS_ERROR)
{
ESP_LOGI(tag, "Entered Alert Bus Error");
}

if (alerts & CAN_ALERT_BUS_OFF)
{
ESP_LOGE(tag, "Bus Off --> Initiate bus recovery");
can_initiate_recovery(); //Needs 128 occurrences of bus free signal
vTaskDelay(pdMS_TO_TICKS(1000));
}

if (alerts & CAN_ALERT_BUS_RECOVERED)
{
//Bus recovery was successful

// only for testing. Does not help !!
esp_err_t res = can_reconfigure_alerts(ALERTS_ENABLED, NULL);
ESP_LOGI(tag, "Bus Recovered %d--> restarting Can", res);

//put can in start state again and re-enable alert monitoring
can_start();
}
}
}

Additionally:

if I recover the situation by completely reinstalling the driver (can_driver_uninstall() / can_driver_install()) instead of using can_initiate_recovery(), the code works propperly and the bus error counters are working as before the recovery..

This is why I assume that this is a bug in the idf can driver. (or maybe I miss something..)

@ICONDev Could it be related to the Bus Off REC errata?

A workaround for that errata has been added v4.3 and later.

Since you are on v3.3.5, could you try modifying the can_intr_handler_err_warn() in components/driver/can.c as follows and see if the issue is resolved:

Thank you for the quick response, seems that this is the issue. I saw that there are further work arounds implemented in the current idf versions in terms of CAN.

Does Espressif intent to update the V3.x release idf with these CAN/TWAI component options (as done in the latest V3 release with the ISR IRAM option) ? Would appreciate it and would like that more than patching the component or using the current idf (which e.g means a lot of additional adaptions and testings of our complete system, also stuff like renaming can to twai and so on..).
Thank you

Juergen