stm32f4 discovery CAN transmit - c

Question

This is my program for CAN transmit. I just want to see through the
oscilloscope wether something is being sent or not. I am using stm32f407
and attolic true studio for it, but i am unable to see any signal on my
tx pin. Kindly tell me where is my mistake. Do i need to connect the transciever externally and also how can i access CAN_H and CAN_L pins.
#include "stm32f4xx.h"
int main(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
RCC_ClocksTypeDef RCC_Clocks;
CAN_InitTypeDef CAN_InitStructure;
CAN_FilterInitTypeDef CAN_FilterInitStructure;
CanTxMsg TxMessage;
RCC_GetClocksFreq(&RCC_Clocks);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);`
GPIO_PinAFConfig(GPIOD, GPIO_PinSource0, GPIO_AF_CAN1);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource1, GPIO_AF_CAN1);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
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(GPIOD, &GPIO_InitStructure);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_CAN1, ENABLE);
CAN_DeInit(CAN1);
CAN_StructInit(&CAN_InitStructure);
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_InitStructure.CAN_BS1 = CAN_BS1_6tq;
CAN_InitStructure.CAN_BS2 = CAN_BS2_7tq;
CAN_InitStructure.CAN_Prescaler = 4;
CAN_Init(CAN1, &CAN_InitStructure);
CAN_FilterInitStructure.CAN_FilterNumber = 0;
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 = CAN_FIFO0;
CAN_FilterInitStructure.CAN_FilterActivation = ENABLE;
CAN_FilterInit(&CAN_FilterInitStructure);
// transmit */
TxMessage.StdId= 0x123;
TxMessage.ExtId= 0x00;
TxMessage.RTR= CAN_RTR_DATA;
TxMessage.IDE= CAN_ID_STD;
TxMessage.DLC= 4;
TxMessage.Data[0]= 0x02;
TxMessage.Data[1]= 0x11;
TxMessage.Data[2]=0x11;
TxMessage.Data[3]=0x11;
while(1)
{
volatile uint_t i;
unit8_t TransmitMailbox= 0;
//sprintf(TxMessage.Data, "Imran\n");
TransmitMailbox= CAN_Transmit(CAN1,&TxMessage);
i=0;
while((CAN_TransmitStatus(CAN1,TransmitMailbox) !=CANTXOK)&& (i !=0xFFFFFF))
{
i++;
}
}
}

Answer 1

Try to turn on the Automatic Wake Up by changing to the following line:
CAN_InitStructure.CAN_AWUM = ENABLE;
The stm32f407 has only the CAN Controller without the internal transciever, so you need to connect it externaly. Also you have to connect another device into your CAN Bus to see something (remember about the terminators).
Please explain what do you mean by saying that:
how can i access CAN_H and CAN_L pins
PS. You should not put each functionality into one routine because it is unreadable.