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Restore functions lost due to inept merging, and refactor to take advantage of them.

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Address the following review feedback items:
 - use stdint types
 - avoid the use of magic numbers (define CYCCNTENA)
 - remove expository comment about sneakiness and corresponding code, replace with something simpler based on the API
 - remove commented/#if 0 code
This commit is contained in:
Mike Smith 2011-07-23 13:53:16 -07:00
parent dae4b44100
commit 0df3bb2c37
1 changed files with 37 additions and 32 deletions
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69
flight/PiOS/STM32F10x/pios_delay.c
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@ -33,9 +33,13 @@
/* Project Includes */
#include <pios.h>
#if defined(PIOS_INCLUDE_DELAY)
/* these should be defined by CMSIS, but they aren't */
#define DWT_CTRL (*(volatile unsigned long *)0xe0001000)
#define DWT_CYCCNT (*(volatile unsigned long *)0xe0001004)
#define DWT_CTRL (*(volatile uint32_t *)0xe0001000)
#define CYCCNTENA (1<<1)
#define DWT_CYCCNT (*(volatile uint32_t *)0xe0001004)
/* cycles per microsecond */
static uint32_t us_ticks;
@ -58,7 +62,7 @@ int32_t PIOS_DELAY_Init(void)
CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
/* enable the CPU cycle counter */
DWT_CTRL |= 1;
DWT_CTRL |= CYCCENTENA;
return 0;
}
@ -76,23 +80,13 @@ int32_t PIOS_DELAY_Init(void)
*/
int32_t PIOS_DELAY_WaituS(uint16_t uS)
{
uint32_t deadline;
uint16_t deadline;
/*
* This logic is mildly sneaky and depends on C's casting behaviour from
* unsigned to signed when the MSB is set.
*
* We also depend on the difference between the deadline and DWT_CYCCNT
* never starting off at more than half of the counter period. Since we
* can't be asked to wait more than 65.5ms, the counter would have to wrap
* in 131ms (approx 32THz for the 32-bit counter) for this to be a problem.
*
* If we are stopped by the debugger for more than half the counter period,
* and the cycle counter doesn't stop (it normally does), the delay will be
* protracted.
*/
deadline = DWT_CYCCNT + (uS * us_ticks);
while ((int32_t)(deadline - DWT_CYCCNT) > 0) {
/* calculate the time at which we should stop waiting */
deadline = PIOS_DELAY_GetuS() + uS;
/* and wait until that time has arrived */
while (PIOS_DELAY_DiffuS(deadline) < 0) {
}
/* No error */
@ -102,10 +96,6 @@ int32_t PIOS_DELAY_WaituS(uint16_t uS)
/**
* Waits for a specific number of mS
*
* If FreeRTOS is configured, and the delay is longer than a tick, wait whole
* ticks using the RTOS. Fractional remainders or periods shorter than a tick
* are busy-waited.
*
* Example:<BR>
* \code
* // Wait for 500 mS
@ -116,15 +106,7 @@ int32_t PIOS_DELAY_WaituS(uint16_t uS)
*/
int32_t PIOS_DELAY_WaitmS(uint16_t mS)
{
#if 0 // XXX cannot do this if the scheduler hasn't started yet...
#ifdef PIOS_INCLUDE_FREERTOS
if (mS > portTICK_RATE_MS) {
vTaskDelay(mS / portTICK_RATE_MS);
mS = mS % portTICK_RATE_MS;
}
#endif
#endif
for (int i = 0; i < mS; i++) {
while (mS--) {
PIOS_DELAY_WaituS(1000);
}
@ -132,6 +114,29 @@ int32_t PIOS_DELAY_WaitmS(uint16_t mS)
return 0;
}
/**
* @brief Query the Delay timer for the current uS
* @return A microsecond value
*/
uint16_t PIOS_DELAY_GetuS()
{
return DWT_CYCCNT / us_ticks;
}
/**
* @brief Compute the difference between now and a reference time
* @param[in] the reference time to compare now to
* @return The number of uS since the delay
*
* @note the user is responsible for worrying about rollover on the 16 bit uS counter
*/
int32_t PIOS_DELAY_DiffuS(uint16_t ref)
{
int32_t ret_t = ref;
return (int16_t) (PIOS_DELAY_GetuS() - ret_t);
}
#endif
/**
* @}