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Leverage some bit timing logic from LPC17xx to the STM32 CAN driver

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4317 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2012-01-20 03:37:29 +00:00
parent e27023f7b1
commit a6d160ea4b
5 changed files with 57 additions and 21 deletions
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8
arch/arm/src/lpc17xx/lpc17_can.c
View File

@ -151,6 +151,10 @@
# define CONFIG_CAN_TSEG2 7
#endif
#if CONFIG_CAN_TSEG2 < 1 || CONFIG_CAN_TSEG2 > CAN_BTR_TSEG2_MAX
# errror "CONFIG_CAN_TSEG2 is out of range"
#endif
#define CAN_BIT_QUANTA (CONFIG_CAN_TSEG1 + CONFIG_CAN_TSEG2 + 1)
/* Debug ********************************************************************/
@ -1127,7 +1131,7 @@ static int can_bittiming(struct up_dev_s *priv)
{
/* At the smallest brp value (1), there are already too few bit times
* (CAN_CLOCK / baud) to meet our goal. brp must be one and we need
* make some reasonalble guesses about ts1 and ts2.
* make some reasonable guesses about ts1 and ts2.
*/
brp = 1;
@ -1153,7 +1157,7 @@ static int can_bittiming(struct up_dev_s *priv)
ts1 = CONFIG_CAN_TSEG1;
ts2 = CONFIG_CAN_TSEG2;
brp = (nclks + (CAN_BIT_QUANTA/2)) / CAN_BIT_QUANTA;
DEBUGASSERT(brp >=1 && brp < 1024);
DEBUGASSERT(brp >=1 && brp <= CAN_BTR_BRP_MAX);
}
sjw = 1;

5
arch/arm/src/lpc17xx/lpc17_can.h
View File

@ -370,9 +370,10 @@
#define CAN_BTR_TSEG2_MASK (7 << CAN_BTR_TSEG2_SHIFT)
#define CAN_BTR_SAM (1 << 23) /* Bit 23: Sampling */
/* Bits 24-31: Reserved */
#define CAN_BTR_BRP_MAX (1024) /* Maximum BTR value (without decrement) */
#define CAN_BTR_TSEG1_MAX (16) /* Maximum TSEG value (without decrement) */
#define CAN_BTR_TSEG2_MAX (8) /* Maximum TSEG value (without decrement) */
#define CAN_BTR_TSEG1_MAX (16) /* Maximum TSEG1 value (without decrement) */
#define CAN_BTR_TSEG2_MAX (8) /* Maximum TSEG2 value (without decrement) */
/* Error Warning Limit */

4
arch/arm/src/stm32/chip/stm32_can.h
View File

@ -358,6 +358,10 @@
#define CAN_BTR_LBKM (1 << 30) /* Bit 30: Loop Back Mode (Debug) */
#define CAN_BTR_SILM (1 << 31) /* Bit 31: Silent Mode (Debug) */
#define CAN_BTR_BRP_MAX (1024) /* Maximum BTR value (without decrement) */
#define CAN_BTR_TSEG1_MAX (16) /* Maximum TSEG1 value (without decrement) */
#define CAN_BTR_TSEG2_MAX (8) /* Maximum TSEG2 value (without decrement) */
/* TX mailbox identifier register */
#define CAN_TIR_TXRQ (1 << 0) /* Bit 0: Transmit Mailbox Request */

38
arch/arm/src/stm32/stm32_can.c
View File

@ -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);

23
arch/arm/src/stm32/stm32_can.h
View File

@ -73,6 +73,29 @@
# error "CONFIG_CAN2_BAUD is not defined"
#endif
/* User-defined TSEG1 and TSEG2 settings may be used.
*
* CONFIG_CAN_TSEG1 = the number of CAN time quanta in segment 1
* CONFIG_CAN_TSEG2 = the number of CAN time quanta in segment 2
* CAN_BIT_QUANTA = The number of CAN time quanta in on bit time
*/
#ifndef CONFIG_CAN_TSEG1
# define CONFIG_CAN_TSEG1 6
#endif
#if CONFIG_CAN_TSEG1 < 1 || CONFIG_CAN_TSEG1 > CAN_BTR_TSEG1_MAX
# errror "CONFIG_CAN_TSEG1 is out of range"
#endif
#ifndef CONFIG_CAN_TSEG2
# define CONFIG_CAN_TSEG2 7
#endif
#if CONFIG_CAN_TSEG2 < 1 || CONFIG_CAN_TSEG2 > CAN_BTR_TSEG2_MAX
# errror "CONFIG_CAN_TSEG2 is out of range"
#endif
/************************************************************************************
* Public Types
************************************************************************************/