Getting problems with CAN on a NUCLEO-F207ZG Board

[ChristianNo]

Hello everyone,

for a project I try to build a small CAN Bus with several Nucleo 144F207 Boards. Sadly, I have a really hard time to get it to work even though it should be rather simple. The minimum setup consists of two boards and two CAN Tranciever PCB's:

https://www.amazon.de/AZDelivery-CAN-Bus-Transceiver-Breakout-Board-Hochgeschwindigkeits-Physische-kompatibel-Standard/dp/B0CBKLH6SS/ref=sr_1_3?keywords=can%2Btransceiver&qid=1701683744&sr=8-3&th=1

Code is configured/generated via the CubeIDE. The Main Funktion looks like this:

Spoiler

int app_main(void)

{

CAN_TxHeaderTypeDef txHeader;

uint8_t txData[8] = {0};

uint32_t txMailbox;

txHeader.IDE = CAN_ID_STD;

txHeader.StdId = 0x2AA;

txHeader.RTR = CAN_RTR_DATA;

txHeader.DLC = 2;

txData[0] = 50;

txData[1] = 0xAA;

CAN_RxHeaderTypeDef rxHeader; //CAN Bus Transmit Header

uint8_t canRX[8] = {0,0,0,0,0,0,0,0}; //CAN Bus Receive Buffer

HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, 0);

// Actual main loop.

while(1)

{

HAL_CAN_AddTxMessage(&hcan1, &txHeader, txData, &txMailbox);

HAL_CAN_GetRxMessage(&hcan1, CAN_RX_FIFO0, &rxHeader, canRX);

if(canRX[1]>0){

HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin); // Toggle LED

}

}

The Identifier is different for each Board.The configuration in CubeIDE looks as follows:

CAN configuration

Both Boards use CAN1. When I run it in Debugging mode and set a Breakpoint at AddTxMessage and then execute the command I get the following Scope Picture:

Rx(yellow),Tx(blue) BUS(Green/Purple))The Tx/Rx lines are at the sending Board in debugging mode. The Rx at the recieving Board gets the signal at the Pin after the Tranciever, but no Arbitration seems to start. I get no other Signals on the bus even with a bigger sampling Window. Does anyone have an Idea why?

[SofLit]

Hello,

These are not correct parameters for CAN bitrate. 

BS1 =1, B2 = 1, Prescaler = 200! -> very low values for BS1 and BS2 and very High prescaler value!

What is the bitrate you're looking for?

[ChristianNo]

Hi,

for testing I was aiming at 50kbit/s. The finished system would be closer to 500kBit/s.

[SofLit]

Ok, first you need to change BS1, BS2 and prescaler values as I've already suggested: maximize BS1 and BS2 values and minimize the prescaler with BS1 ~=75% (BS1+BS2)

[SofLit · Accepted solution]

Attached a proposal of CAN bitrate communication @500Kb/s

[ChristianNo]

The Provided configuration worked! Thanks for your help!