openpilot_comma/board/drivers/llcan.h

// this is needed for 1 mbps support
#define CAN_QUANTA 8U
#define CAN_SEQ1 6 // roundf(quanta * 0.875f) - 1;
#define CAN_SEQ2 1 // roundf(quanta * 0.125f);

#define CAN_PCLK 24000U
// 333 = 33.3 kbps
// 5000 = 500 kbps
#define can_speed_to_prescaler(x) (CAN_PCLK / CAN_QUANTA * 10U / (x))

#define GET_BUS(msg) (((msg)->RDTR >> 4) & 0xFF)
#define GET_LEN(msg) ((msg)->RDTR & 0xF)
#define GET_ADDR(msg) ((((msg)->RIR & 4) != 0) ? ((msg)->RIR >> 3) : ((msg)->RIR >> 21))
#define GET_BYTE(msg, b) (((int)(b) > 3) ? (((msg)->RDHR >> (8U * ((unsigned int)(b) % 4U))) & 0XFFU) : (((msg)->RDLR >> (8U * (unsigned int)(b))) & 0xFFU))
#define GET_BYTES_04(msg) ((msg)->RDLR)
#define GET_BYTES_48(msg) ((msg)->RDHR)

void puts(const char *a);

bool llcan_set_speed(CAN_TypeDef *CAN_obj, uint32_t speed, bool loopback, bool silent) {
  // initialization mode
  register_set(&(CAN_obj->MCR), CAN_MCR_TTCM | CAN_MCR_INRQ, 0x180FFU);
  while((CAN_obj->MSR & CAN_MSR_INAK) != CAN_MSR_INAK);

  // set time quanta from defines
  register_set(&(CAN_obj->BTR), ((CAN_BTR_TS1_0 * (CAN_SEQ1-1)) |
            (CAN_BTR_TS2_0 * (CAN_SEQ2-1)) |
            (can_speed_to_prescaler(speed) - 1U)), 0xC37F03FFU);

  // silent loopback mode for debugging
  if (loopback) {
    register_set_bits(&(CAN_obj->BTR), CAN_BTR_SILM | CAN_BTR_LBKM);
  }
  if (silent) {
    register_set_bits(&(CAN_obj->BTR), CAN_BTR_SILM);
  }

  // reset
  register_set(&(CAN_obj->MCR), CAN_MCR_TTCM | CAN_MCR_ABOM, 0x180FFU);

  #define CAN_TIMEOUT 1000000
  int tmp = 0;
  bool ret = false;
  while(((CAN_obj->MSR & CAN_MSR_INAK) == CAN_MSR_INAK) && (tmp < CAN_TIMEOUT)) tmp++;
  if (tmp < CAN_TIMEOUT) {
    ret = true;
  }

  return ret;
}

void llcan_init(CAN_TypeDef *CAN_obj) {
  // Enter init mode
  register_set_bits(&(CAN_obj->FMR), CAN_FMR_FINIT);
  
  // Wait for INAK bit to be set
  while(((CAN_obj->MSR & CAN_MSR_INAK) == CAN_MSR_INAK)) {}

  // no mask
  // For some weird reason some of these registers do not want to set properly on CAN2 and CAN3. Probably something to do with the single/dual mode and their different filters.
  CAN_obj->sFilterRegister[0].FR1 = 0U;
  CAN_obj->sFilterRegister[0].FR2 = 0U;
  CAN_obj->sFilterRegister[14].FR1 = 0U;
  CAN_obj->sFilterRegister[14].FR2 = 0U;
  CAN_obj->FA1R |= 1U | (1U << 14);

  // Exit init mode, do not wait
  register_clear_bits(&(CAN_obj->FMR), CAN_FMR_FINIT);

  // enable certain CAN interrupts
  register_set_bits(&(CAN_obj->IER), CAN_IER_TMEIE | CAN_IER_FMPIE0 |  CAN_IER_WKUIE);

  if (CAN_obj == CAN1) {
    NVIC_EnableIRQ(CAN1_TX_IRQn);
    NVIC_EnableIRQ(CAN1_RX0_IRQn);
    NVIC_EnableIRQ(CAN1_SCE_IRQn);
  } else if (CAN_obj == CAN2) {
    NVIC_EnableIRQ(CAN2_TX_IRQn);
    NVIC_EnableIRQ(CAN2_RX0_IRQn);
    NVIC_EnableIRQ(CAN2_SCE_IRQn);
#ifdef CAN3
  } else if (CAN_obj == CAN3) {
    NVIC_EnableIRQ(CAN3_TX_IRQn);
    NVIC_EnableIRQ(CAN3_RX0_IRQn);
    NVIC_EnableIRQ(CAN3_SCE_IRQn);
#endif
  } else {
    puts("Invalid CAN: initialization failed\n");
  }
}

void llcan_clear_send(CAN_TypeDef *CAN_obj) {
  CAN_obj->TSR |= CAN_TSR_ABRQ0;
  register_clear_bits(&(CAN_obj->MSR), CAN_MSR_ERRI);
  // cppcheck-suppress selfAssignment ; needed to clear the register
  CAN_obj->MSR = CAN_obj->MSR;
}