Hi, let me clarify more my situation … I am coding this from scratch i am using a CAN transciever…My problem is that the CAN_Start function always returns an Error and while debugging i noticed that my code is stuck in the CAN initialisation what i see is that the BIT INAK in the MSR register stayd always 1 when it should switch to 0…probably i have a problem in the config …This is my config code :

void can_gpio_init(void) {
/*1 Enable Clock Access to GPIOB*/
RCC->AHB1ENR |= GPIODEN;
/*2 Set PD0 and PD1 to alternate function mode*/
GPIOD->MODER &=~(1U<<0); GPIOD->MODER |=(1U<<1); GPIOD->MODER &=~(1U<<2); GPIOD->MODER |=(1U<<3); GPIOD->PUPDR |=(1U<<0); GPIOD->PUPDR &=~(1U<<1); GPIOD->PUPDR |=(1U<<2); GPIOD->PUPDR &=~(1U<<3); GPIOD->OTYPER &=~(1U<<0); GPIOD->OTYPER &=~(1U<<1); /*3 SET PD0 and PD1 alternate function to CAN1 RX and TX*/ GPIOD->AFR[0] = (CAN_AF<<0); GPIOD->AFR[0]= (CAN_AF<<4); /*4 Enable CAN RX0 Interrupt for message reception*/ NVIC_EnableIRQ(CAN1_RX0_IRQn); } void can_parms_init(uint8_t mode){ /*1 Enable Clock Access to CAN1*/ RCC->APB1ENR |= RCC_APB1ENR_CAN1EN;
/*2 Enter Initialization mode*/
CAN1->MCR |= CAN_MCR_INRQ;
/*3 Wait until CAN1 is in Initialization mode*/
while ((CAN1->MSR & CAN_MSR_INAK)==0) {}
/*4 Exit Sleep Mode*/
CAN1->MCR &=~ CAN_MCR_SLEEP;
/*5 Wait until CAN1 is OUT of Sleep Mode*/
while ((CAN1->MSR & CAN_MSR_SLAK)) {}
/*5 Configure timing parameters including baudrate by configuring time segment 1 and 2 and prescaler*/
CAN1->BTR = (11<< CAN_BTR_TS1_Pos) | (2 << CAN_BTR_TS2_Pos) | (5 << CAN_BTR_BRP_Pos); /*6 Select Mode*/ if (mode) { /*Normal Mode*/ CAN1->BTR &=~(1<<30); } else { //loopBack mode CAN1->BTR |=(1<<30); } }

there are the basic steps to configure
1. Leave sleep mode
2. Enter Initialization Mode
3. Configure BaudRAte
4. Configure other things as you need
5. Exit from Initialization mode