The CAN Unit is not the problem. If I hook up a logic analyzer at the connection between Core and CAN Unit the data is fine.

#include <M5Core2.h>
#include "CAN_config.h"
#include "ESP32CAN.h"

CAN_device_t CAN_cfg; // CAN Config
unsigned long previousMillis = 0; // will store last time a CAN Message was send
const int interval = 1000; // interval at which send CAN Messages (milliseconds)
const int rx_queue_size = 10; // Receive Queue size

uint8_t count = 0;

void setup() {
M5.begin(false,false,true,false); //(LCDEnable, SDEnable, SerialEnable, I2CEnable)
CAN_cfg.speed = CAN_SPEED_250KBPS;
CAN_cfg.tx_pin_id = GPIO_NUM_32;
CAN_cfg.rx_pin_id = GPIO_NUM_33;
CAN_cfg.rx_queue = xQueueCreate(rx_queue_size, sizeof(CAN_frame_t));
ESP32Can.CANInit();
}

void loop() {
CAN_frame_t rx_frame;
unsigned long currentMillis = millis();

// Receive next CAN frame from queue
if (xQueueReceive(CAN_cfg.rx_queue, &rx_frame, 3 * portTICK_PERIOD_MS) == pdTRUE) {

if (rx_frame.FIR.B.RTR == CAN_RTR) {
  Serial.printf("RTR from 0x%08X, DLC %d\r\n", rx_frame.MsgID,  rx_frame.FIR.B.DLC);
}
else {
  Serial.printf("from 0x%08X, DLC %d, Data \r\n", rx_frame.MsgID,  rx_frame.FIR.B.DLC);
  for (int i = 0; i < rx_frame.FIR.B.DLC; i++) {
    Serial.printf("0x%02X ", rx_frame.data.u8[i]);
  }
  Serial.println("\n");
}

}
}

sorry, I am out of ideas and I don't have the CAN-bus unit so I cannot test myself.

Good luck!
Felix

I checked my code and it is false.
M5.begin(true,false,true,false);

It doesn't work even if all are false...
M5.begin(false,false,false,false);

It is the same even if all are true
M5.begin(true,true,true,true);

Thanks your reply.
hide4849

you also need to make sure external I2C (using 32 and 33) does not get initialized, e.g. fourth parameter of M5.begin() should to be false (which is the default).

Thanks
Felix

Is there any more other place to reconfigure?

Thanks your reply.
hide4849

the CAN bus unit uses a serial connection which by default is available on M5Stack Groove Port B. However M5Core2 (w/o M5GO battery bottom 2) only has a Port A which by default is used for I2C.

So you either can try to reconfigure M5Core2 Port A from I2C to serial or stack an M5GO battery bottom 2 to your M5Core2 which then gives you Port B (and C).

Thanks
Felix