Ah sure.
Please allow me to provide you with more information: my project is simply to get some data from the host computer and then display it on the screen through the LVGL library. The peripherals used include SDRAM, an LTDC screen and some less important ICs (such as IO expansion). These peripherals are provided with ready-made driver files, so I did not initialize them manually in CubeMX, but directly used the functions provided by the driver files.
For the schematic diagram,: The CAN of the STM32F4 is connected to the SIT1042T/TPT1051V transceiver chip through the setting of P9 (a jumper cap), and then connected to the external CAN bus through the terminal block. CAN and USB share PA11 and PA12, so they cannot be used at the same time, and I have confirmed that the USB function is disabled and the jumper cap has been correctly connected externally.
Based on other people's advice, I did some more testing on my project this morning:
1. I disabled the interrupt function and used polling to get CAN messages in the while(1) loop in main.c. The corresponding function is:
uint8_t can_receive_msg(uint32_t id, uint8_t *buf)
{
if (HAL_CAN_GetRxFifoFillLevel(&hcan1, CAN_RX_FIFO0) == 0)
{
return 0;
}
if (HAL_CAN_GetRxMessage(&hcan1, CAN_RX_FIFO0, &RxHeader, buf) != HAL_OK)
{
return 0;
}
if (RxHeader.StdId != id || RxHeader.IDE != CAN_ID_STD || RxHeader.RTR != CAN_RTR_DATA)
{
return 0;
}
return RxHeader.DLC;
}
Then, I enabled the Loopback mode to confirm that CAN can send and receive data normally, stably and for a long time in Loopback mode
2. I used an oscilloscope to monitor the signal on the bus, connecting the X end of the oscilloscope to CANH and the Y end to CANL. The situation is very interesting:
2a: Without connecting the cable, start the host computer and start CAN transmission, the waveform on the bus is normal; then, connect the CAN cable to the STM32 board that has been powered on, the signal waveform on the CAN cable disappears, and even after unplugging the cable from the STM32 board, the signal cannot be reset
2b: Start the host computer and start CAN transmission, then connect the cable to the STM32 board that has not been powered on, the CAN bus signal displays normally; keep the cable connected, and then power on the STM32 board, the STM32 can read the data on the CAN normally and display it on the screen, but about 10s-45s later (this time is very random), the signal on the CAN bus suddenly disappears and cannot be restored
2c: If you connect the cable first, then power on the STM32 board, and then start the host computer and start CAN transmission, then the STM32 will only be able to read the first data frame, and then the bus signal disappears immediately and cannot be restored.
