Difficulty enabling CAN on ESP32

Question

I am currently trying to implement CAN on an ESP32. Here is my code:

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/twai.h"
#include "esp_err.h"

#define TAG "CAN_TX"

// Define CAN pins
#define CAN_TX_PIN GPIO_NUM_5
#define CAN_RX_PIN GPIO_NUM_4

void app_main(void)
{
    // Configurations
    const twai_general_config_t g_config = TWAI_GENERAL_CONFIG_DEFAULT(CAN_TX_PIN, CAN_RX_PIN, TWAI_MODE_NORMAL);
    const twai_timing_config_t t_config = TWAI_TIMING_CONFIG_500KBITS();
    const twai_filter_config_t f_config = TWAI_FILTER_CONFIG_ACCEPT_ALL();

    // Install and start driver
    if (twai_driver_install(&g_config, &t_config, &f_config) != ESP_OK) {
        printf("Failed to install TWAI driver: %s\n", esp_err_to_name(twai_driver_install(&g_config, &t_config, &f_config)));
        return;
    }

    if (twai_start() != ESP_OK) {
        printf("Failed to start TWAI driver: %s\n", esp_err_to_name(twai_start()));
        return;
    }

    printf("TWAI driver started. Beginning transmission...\n");

    // Create message
    twai_message_t message = {
        .identifier = 0x123,
        .data_length_code = 8,
        .data = {0, 1, 2, 3, 4, 5, 6, 7},
        .flags = 0
    };

    while (1) {
        esp_err_t result = twai_transmit(&message, pdMS_TO_TICKS(1000));
        if (result == ESP_OK) {
            //printf("Message sent\n"); // Remove or slow down this print.
        } else {
            printf("Failed to send message: %s\n", esp_err_to_name(result));
        }

        vTaskDelay(pdMS_TO_TICKS(1000)); // Send every 1 second
    }
}

Here is what the terminal returns:

TWAI driver started. Beginning transmission...
Failed to send message: ESP_ERR_TIMEOUT
Failed to send message: ESP_ERR_TIMEOUT
Failed to send message: ESP_ERR_TIMEOUT

And it continues with this error, and I'm not sure what to do about it. If it’s a hardware issue or software issue. How can I fix it?

Thank you for the quick response back. To clarify this is my second day of utilizing examples, an oscilloscope and esp32 documentation to try and get this working. I have had no luck yet. If you know of any projects that do function with can that are not Arduino based please send the link. Thank you again! — Antonio Ristevski
– Antonio Ristevski, Commented Apr 7 at 8:36
Is there activity on the Tx pin of the MCU? Are there ACK bits getting set on the live bus CANH/CANL? — Lundin
– Lundin, Commented Apr 7 at 10:36

Peter Mortensen · Accepted Answer · 2025-10-19 16:38:17Z

0

This is most likely a hardware issue. Make sure that

Your CAN transceiver has power and is correctly wired up (RX/TX might be mixed up)
Your CAN bus has proper termination (120 ohm at both ends)
Your CAN bus has at least one additional participant (to send the ACKs)
Your CAN bus participants agree on the bus bitrate.

edited Oct 19 at 16:38

Peter Mortensen

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answered May 6 at 16:27

DrMickeyLauer

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