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Fix issue with LPC17xx CAN baud calculation

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4269 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2012-01-06 15:58:30 +00:00
parent aa80eeff95
commit 6d6cf4daf8
1 changed files with 11 additions and 8 deletions
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19
arch/arm/src/lpc17xx/lpc17_can.c
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@ -157,10 +157,9 @@
#endif
/* Timing *******************************************************************/
/* CAN clocking is provided at CCLK/4 (hardcoded in lpc17_caninitialize()) */
/* CAN clocking is provided at CCLK divided by the configured divisor */
#define CAN_CCLK_DIVISOR 4
#define CAN_CLOCK_FREQUENCY (LPC17_CCLK / CAN_CCLK_DIVISOR)
#define CAN_CLOCK_FREQUENCY(d) ((uint32_t)LPC17_CCLK / (uint32_t)(d))
/****************************************************************************
* Private Types
@ -168,9 +167,10 @@
struct up_dev_s
{
uint8_t port; /* CAN port number */
uint32_t baud; /* Configured baud */
uint32_t base; /* CAN register base address */
uint8_t port; /* CAN port number */
uint8_t divisor; /* CCLK divisor (numeric value) */
uint32_t baud; /* Configured baud */
uint32_t base; /* CAN register base address */
};
/****************************************************************************
@ -235,6 +235,7 @@ static const struct can_ops_s g_canops =
static struct up_dev_s g_can1priv =
{
.port = 1,
.divisor = CONFIG_CAN1_DIVISOR,
.baud = CONFIG_CAN1_BAUD,
.base = LPC17_CAN1_BASE,
};
@ -250,6 +251,7 @@ static struct can_dev_s g_can1dev =
static struct up_dev_s g_can2priv =
{
.port = 2,
.divisor = CONFIG_CAN2_DIVISOR,
.baud = CONFIG_CAN2_BAUD,
.base = LPC17_CAN2_BASE,
};
@ -1020,7 +1022,8 @@ static int can_bittiming(struct up_dev_s *priv)
uint32_t ts2;
uint32_t sjw;
canllvdbg("CAN%d PCLK1: %d baud: %d\n", priv->port, CAN_CLOCK_FREQUENCY, priv->baud);
canllvdbg("CAN%d PCLK1: %d baud: %d\n", priv->port,
CAN_CLOCK_FREQUENCY(priv->divisor), 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.
@ -1039,7 +1042,7 @@ static int can_bittiming(struct up_dev_s *priv)
* PCLK1 = 42,000,000 baud = 700,000 nquanta = 14 : brp = 4
*/
canbtr = CAN_CLOCK_FREQUENCY / priv->baud;
canbtr = CAN_CLOCK_FREQUENCY(priv->divisor) / priv->baud;
if (canbtr < 14)
{
/* At the smallest brp value (1), there are already fewer bit times