容错率计算就是把这个函数做了lua的实现,此函数来自CMSIS-Driver
[C] 纯文本查看 复制代码 /**
\fn int32_t CANx_SetBitrate (ARM_CAN_BITRATE_SELECT select, uint32_t bitrate, uint32_t bit_segments, uint8_t x)
\brief Set bitrate for CAN interface.
\param[in] select Bitrate selection
- ARM_CAN_BITRATE_NOMINAL : nominal (flexible data-rate arbitration) bitrate
- ARM_CAN_BITRATE_FD_DATA : flexible data-rate data bitrate
\param[in] bitrate Bitrate
\param[in] bit_segments Bit segments settings
\param[in] x Controller number (0..1)
\return execution status
*/
static int32_t CANx_SetBitrate (ARM_CAN_BITRATE_SELECT select, uint32_t bitrate, uint32_t bit_segments, uint8_t x) {
FDCAN_GlobalTypeDef *ptr_CAN;
uint32_t cccr, sjw, prop_seg, phase_seg1, phase_seg2, pclk, brp, brp_max, tq_num;
if (x >= CAN_CTRL_NUM) { return ARM_DRIVER_ERROR; }
if ((select != ARM_CAN_BITRATE_NOMINAL) && (select != ARM_CAN_BITRATE_FD_DATA) ) { return ARM_CAN_INVALID_BITRATE_SELECT; }
if (can_driver_powered[x] == 0U) { return ARM_DRIVER_ERROR; }
prop_seg = (bit_segments & ARM_CAN_BIT_PROP_SEG_Msk ) >> ARM_CAN_BIT_PROP_SEG_Pos;
phase_seg1 = (bit_segments & ARM_CAN_BIT_PHASE_SEG1_Msk) >> ARM_CAN_BIT_PHASE_SEG1_Pos;
phase_seg2 = (bit_segments & ARM_CAN_BIT_PHASE_SEG2_Msk) >> ARM_CAN_BIT_PHASE_SEG2_Pos;
sjw = (bit_segments & ARM_CAN_BIT_SJW_Msk ) >> ARM_CAN_BIT_SJW_Pos;
if (select == ARM_CAN_BITRATE_NOMINAL) {
if (((prop_seg + phase_seg1) < 2U) || ((prop_seg + phase_seg1) > 256U)) { return ARM_CAN_INVALID_BIT_PROP_SEG; }
if (( phase_seg2 < 1U) || ( phase_seg2 > 128U)) { return ARM_CAN_INVALID_BIT_PHASE_SEG2; }
if (( sjw < 1U) || ( sjw > 128U)) { return ARM_CAN_INVALID_BIT_SJW; }
brp_max = 512U;
} else {
if (((prop_seg + phase_seg1) < 2U) || ((prop_seg + phase_seg1) > 32U)) { return ARM_CAN_INVALID_BIT_PROP_SEG; }
if (( phase_seg2 < 1U) || ( phase_seg2 > 16U)) { return ARM_CAN_INVALID_BIT_PHASE_SEG2; }
if (( sjw < 1U) || ( sjw > 8U)) { return ARM_CAN_INVALID_BIT_SJW; }
brp_max = 32U;
}
tq_num = 1U + prop_seg + phase_seg1 + phase_seg2;
pclk = CAN_GetClock (); if (pclk == 0U) { return ARM_DRIVER_ERROR; }
brp = pclk / (tq_num * bitrate); if (brp > brp_max) { return ARM_CAN_INVALID_BITRATE; }
if (pclk > (brp * tq_num * bitrate)) {
if ((((pclk - (brp * tq_num * bitrate)) * 1024U) / pclk) > CAN_CLOCK_TOLERANCE) { return ARM_CAN_INVALID_BITRATE; }
} else if (pclk < (brp * tq_num * bitrate)) {
if (((((brp * tq_num * bitrate) - pclk) * 1024U) / pclk) > CAN_CLOCK_TOLERANCE) { return ARM_CAN_INVALID_BITRATE; }
}
ptr_CAN = ptr_regs_CANx[x];
cccr = ptr_CAN->CCCR;
if ((cccr & (FDCAN_CCCR_CCE | FDCAN_CCCR_INIT)) != (FDCAN_CCCR_CCE | FDCAN_CCCR_INIT)) {
ptr_CAN->CCCR = FDCAN_CCCR_CCE | // Configuration change enable
FDCAN_CCCR_INIT ; // Initialization
while ((ptr_CAN->CCCR & FDCAN_CCCR_INIT) == 0U);
}
if (select == ARM_CAN_BITRATE_NOMINAL) {
ptr_CAN->NBTP = ((brp - 1U) << 16) | ((prop_seg + phase_seg1 - 1U) << 8) | (phase_seg2 - 1U) | ((sjw - 1U) << 25);
} else {
ptr_CAN->DBTP = ((brp - 1U) << 16) | ((prop_seg + phase_seg1 - 1U) << 8) | ((phase_seg2 - 1U) << 4) | (sjw - 1U);
}
ptr_CAN->CCCR = cccr;
return ARM_DRIVER_OK;
}
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