Posted on July 13, 2012 at 15:57Hi all,
I am trying to get the CAN interface working on the STM32F4DISCOVERY board.
After calling the configuration functions from the peripheral library, when I tried to transmit message with just a oscilloscope connected to the TX and RX pins it does not work. I tried usng CAN_TransmitStatus() to see the status of the mailbox and it returned ''pending''. Then I tracked down the register in the CAN controller, the error flag is up and further more it says ''BIT DOMINANT error''...
I don't know if I need to connect to a transceiver first and hook this board onto a CAN bus before I test it out? Or is it just something wrong with the configuration.
Here is the code I had for the configuration part:
---(I just used GPIOE pin0 to see if the program is running, nothing else)
/* Enable GPIO clock */
RCC_AHB1PeriphClockCmd(CAN_GPIO_CLK|RCC_AHB1Periph_GPIOE, ENABLE);
/* Connect CAN pins to AF9 */
GPIO_PinAFConfig(CAN_GPIO_PORT, CAN_RX_SOURCE, CAN_AF_PORT);
GPIO_PinAFConfig(CAN_GPIO_PORT, CAN_TX_SOURCE, CAN_AF_PORT);
/* Configure CAN RX and TX pins */
GPIO_InitStructure.GPIO_Pin = CAN_RX_PIN | CAN_TX_PIN;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(CAN_GPIO_PORT, &GPIO_InitStructure);
//RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
//configure a pin for debug
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOE, &GPIO_InitStructure);
/* CAN configuration ********************************************************/
/* Enable CAN clock */
RCC_APB1PeriphClockCmd(CAN_CLK, ENABLE);
/* CAN register init */
CAN_DeInit(CANx);
/* CAN cell init */
CAN_InitStructure.CAN_TTCM = DISABLE;
CAN_InitStructure.CAN_ABOM = DISABLE;
CAN_InitStructure.CAN_AWUM = DISABLE;
CAN_InitStructure.CAN_NART = DISABLE;
CAN_InitStructure.CAN_RFLM = DISABLE;
CAN_InitStructure.CAN_TXFP = DISABLE;
CAN_InitStructure.CAN_Mode = CAN_Mode_Normal;
CAN_InitStructure.CAN_SJW = CAN_SJW_1tq;
/* CAN Baudrate = 1 MBps (CAN clocked at 30 MHz) */
CAN_InitStructure.CAN_BS1 = CAN_BS1_6tq;
CAN_InitStructure.CAN_BS2 = CAN_BS2_8tq;
CAN_InitStructure.CAN_Prescaler = 2;
CAN_Init(CANx, &CAN_InitStructure);
/* CAN filter init */
#ifdef USE_CAN1
CAN_FilterInitStructure.CAN_FilterNumber = 0;
#else /* USE_CAN2 */
CAN_FilterInitStructure.CAN_FilterNumber = 14;
#endif /* USE_CAN1 */
CAN_FilterInitStructure.CAN_FilterMode = CAN_FilterMode_IdMask;
CAN_FilterInitStructure.CAN_FilterScale = CAN_FilterScale_32bit;
CAN_FilterInitStructure.CAN_FilterIdHigh = 0x0000;
CAN_FilterInitStructure.CAN_FilterIdLow = 0x0000;
CAN_FilterInitStructure.CAN_FilterMaskIdHigh = 0x0000;
CAN_FilterInitStructure.CAN_FilterMaskIdLow = 0x0000;
CAN_FilterInitStructure.CAN_FilterFIFOAssignment = 0;
CAN_FilterInitStructure.CAN_FilterActivation = ENABLE;
CAN_FilterInit(&CAN_FilterInitStructure);
/* Transmit Structure preparation */
TxMessage.StdId = 0x321;
TxMessage.ExtId = 0x01;
TxMessage.RTR = CAN_RTR_DATA;
TxMessage.IDE = CAN_ID_STD;
TxMessage.DLC = 1;
/* Enable FIFO 0 message pending Interrupt */
CAN_ITConfig(CANx, CAN_IT_FMP0, ENABLE);
Any help is very appreciated. Thanks!
Keybo
