diff options
Diffstat (limited to 'nuttx/arch/arm/src/stm32/stm32_can.c')
| -rwxr-xr-x | nuttx/arch/arm/src/stm32/stm32_can.c | 38 |
1 files changed, 21 insertions, 17 deletions
diff --git a/nuttx/arch/arm/src/stm32/stm32_can.c b/nuttx/arch/arm/src/stm32/stm32_can.c index 9cd6c5712..8f5a6b8b1 100755 --- a/nuttx/arch/arm/src/stm32/stm32_can.c +++ b/nuttx/arch/arm/src/stm32/stm32_can.c @@ -74,6 +74,10 @@ #define CAN_ALL_MAILBOXES (CAN_TSR_TME0 | CAN_TSR_TME1 | CAN_TSR_TME2) +/* Bit timing ***************************************************************/ + +#define CAN_BIT_QUANTA (CONFIG_CAN_TSEG1 + CONFIG_CAN_TSEG2 + 1) + /* Debug ********************************************************************/ /* Non-standard debug that may be enabled just for testing CAN */ @@ -1259,14 +1263,13 @@ static int can_bittiming(struct stm32_can_s *priv) canllvdbg("CAN%d PCLK1: %d baud: %d\n", priv->port, STM32_PCLK1_FREQUENCY, priv->baud); - /* Try to get 14 quanta in one bit_time. That is based on the idea that the ideal - * would be ts1=6 nd ts2=7 and (1 + ts1 + ts2) = 14. + /* Try to get CAN_BIT_QUANTA quanta in one bit_time. * - * bit_time = Tq*(1 +ts1 + ts2) - * nquanta = bit_time/Tq - * nquanta = (1 +ts1 + ts2) + * bit_time = Tq*(ts1 + ts2 + 1) + * nquanta = bit_time / Tq + * nquanta = (ts1 + ts2 + 1) * - * bit_time = brp * Tpclk1 * (1 + ts1 + ts2) + * bit_time = brp * Tpclk1 * (ts1 + ts2 + 1) * nquanta = bit_time / brp / Tpclk1 * = PCLK1 / baud / brp * brp = PCLK1 / baud / nquanta; @@ -1277,11 +1280,11 @@ static int can_bittiming(struct stm32_can_s *priv) */ tmp = STM32_PCLK1_FREQUENCY / priv->baud; - if (tmp < 14) + if (tmp < CAN_BIT_QUANTA) { - /* At the smallest brp value (1), there are already fewer bit times - * (PCLCK1 / baud) is already smaller than our goal. brp must be one - * and we need make some reasonalble guesses about ts1 and ts2. + /* At the smallest brp value (1), there are already too few bit times + * (PCLCK1 / baud) to meet our goal. brp must be one and we need + * make some reasonable guesses about ts1 and ts2. */ brp = 1; @@ -1290,23 +1293,24 @@ static int can_bittiming(struct stm32_can_s *priv) ts1 = (tmp - 1) >> 1; ts2 = tmp - ts1 - 1; - if (ts1 == ts2 && ts1 > 1 && ts2 < 16) + if (ts1 == ts2 && ts1 > 1 && ts2 < CAN_BTR_TSEG2_MAX) { ts1--; ts2++; } } - /* Otherwise, nquanta is 14, ts1 is 6, ts2 is 7 and we calculate brp to - * achieve 14 quanta in the bit time + /* Otherwise, nquanta is CAN_BIT_QUANTA, ts1 is CONFIG_CAN_TSEG1, ts2 is + * CONFIG_CAN_TSEG2 and we calculate brp to achieve CAN_BIT_QUANTA quanta + * in the bit time */ else { - ts1 = 6; - ts2 = 7; - brp = tmp / 14; - DEBUGASSERT(brp >=1 && brp < 1024); + ts1 = CONFIG_CAN_TSEG1; + ts2 = CONFIG_CAN_TSEG2; + brp = (tmp + (CAN_BIT_QUANTA/2)) / CAN_BIT_QUANTA; + DEBUGASSERT(brp >=1 && brp <= CAN_BTR_BRP_MAX); } canllvdbg("TS1: %d TS2: %d BRP: %d\n", ts1, ts2, brp); |