STM32F7 CAN Stuck in Normal Mode Acknowledge After Baudrate Change

[ramji]

Hello,

I’m using STM32F746 with CAN1 peripheral in Normal mode, and facing an issue during runtime:

• when the master and slave device communicate at baud rate of 1Mbps and if I change the baud rate of master device to any other baud rate then then gets stuck in a while loop waiting for Normal Mode acknowledgment:

// Enter Normal Mode
CAN1->MCR &= ~CAN_MCR_INRQ;
while ((CAN1->MSR & CAN_MSR_INAK) == CAN_MSR_INAK); // stuck here

What I've Done:

• I perform a software reset before reinitializing CAN:

  RCC->APB1RSTR |= RCC_APB1RSTR_CAN1RST;

  RCC->APB1RSTR &= ~RCC_APB1RSTR_CAN1RST;

• I cleared the BUS-OFF condition manually:

  if (CAN1->ESR & CAN_ESR_BOFF)

  { CAN1->ESR = 0; }

• I enabled auto bus-off recovery:

  CAN1->MCR |= CAN_MCR_ABOM;

• CAN is configured in Normal mode, with filters set and interrupts enabled.

Problem:

After the master changes its baud rate, the STM32 re-initializes, but hangs at the wait for Normal mode acknowledge.

Question:

• Is there something else needed to recover cleanly from this situation?

• Do I need to delay or detect bus idle before exiting INIT mode?

• Any additional register I should clear or sequence to follow?

Any suggestions or official guidance would be appreciated.