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STM-can-api: Added usage of prescaler 

- This enables more frequencies, but without regard to the accuracy.
May still require manual clock setup, to remain in tolerance window
pull/13565/head
m-ecry 2020-09-14 16:29:12 +02:00
parent 35c9e7a5ad
commit 13b663397f
1 changed files with 26 additions and 1 deletions
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27
targets/TARGET_STM/can_api.c
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@ -135,12 +135,24 @@ static void _can_init_freq_direct(can_t *obj, const can_pinmap_t *pinmap, int hz
int ntq = 10000000 / hz;
#endif
int nominalPrescaler = 1;
// !When the sample point should be lower than 50%, this must be changed to
// !IS_FDCAN_NOMINAL_TSEG2(ntq/nominalPrescaler), since
// NTSEG2 and SJW max values are lower. For now the sample point is fix @75%
while (!IS_FDCAN_NOMINAL_TSEG1(ntq/nominalPrescaler)){
nominalPrescaler ++;
if (!IS_FDCAN_NOMINAL_PRESCALER(nominalPrescaler)){
error("Could not determine good nominalPrescaler. Bad clock value\n");
}
}
ntq = ntq/nominalPrescaler;
obj->CanHandle.Init.FrameFormat = FDCAN_FRAME_CLASSIC;
obj->CanHandle.Init.Mode = FDCAN_MODE_NORMAL;
obj->CanHandle.Init.AutoRetransmission = ENABLE;
obj->CanHandle.Init.TransmitPause = DISABLE;
obj->CanHandle.Init.ProtocolException = ENABLE;
obj->CanHandle.Init.NominalPrescaler = 1; // Prescaler
obj->CanHandle.Init.NominalPrescaler = nominalPrescaler; // Prescaler
obj->CanHandle.Init.NominalTimeSeg1 = ntq * 0.75; // Phase_segment_1
obj->CanHandle.Init.NominalTimeSeg2 = ntq - 1 - obj->CanHandle.Init.NominalTimeSeg1; // Phase_segment_2
obj->CanHandle.Init.NominalSyncJumpWidth = obj->CanHandle.Init.NominalTimeSeg2; // Synchronization_Jump_width
@ -278,6 +290,19 @@ int can_frequency(can_t *obj, int f)
int ntq = 10000000 / hz;
#endif
int nominalPrescaler = 1;
// !When the sample point should be lower than 50%, this must be changed to
// !IS_FDCAN_DATA_TSEG2(ntq/nominalPrescaler), since
// NTSEG2 and SJW max values are lower. For now the sample point is fix @75%
while (!IS_FDCAN_DATA_TSEG1(ntq/nominalPrescaler)){
nominalPrescaler ++;
if (!IS_FDCAN_NOMINAL_PRESCALER(nominalPrescaler)){
error("Could not determine good nominalPrescaler. Bad clock value\n");
}
}
ntq = ntq/nominalPrescaler;
obj->CanHandle.Init.NominalPrescaler = nominalPrescaler;
obj->CanHandle.Init.NominalTimeSeg1 = ntq * 0.75; // Phase_segment_1
obj->CanHandle.Init.NominalTimeSeg2 = ntq - 1 - obj->CanHandle.Init.NominalTimeSeg1; // Phase_segment_2
obj->CanHandle.Init.NominalSyncJumpWidth = obj->CanHandle.Init.NominalTimeSeg2; // Synchronization_Jump_width