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second round of changes at replacing app_timer with RTC

pull/932/head
Rohit Grover 2015-02-13 09:07:24 +00:00
parent e6a7c6f648
commit 2ee04fde1f
1 changed files with 24 additions and 34 deletions
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58
libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/us_ticker.c
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@ -22,11 +22,25 @@
#include "nrf_delay.h"
#include "app_util_platform.h"
/*
* Note: The micro-second timer API on the nRF51 platform is implemented using
* the RTC counter run at 32kHz (sourced from an external oscillator). This is
* a trade-off between precision and power. Running a normal 32-bit MCU counter
* at high frequency causes the average power consumption to rise to a few
* hundred micro-amps, which is prohibitive for typical low-power BLE
* applications.
* A 32kHz clock doesn't offer the precision needed for keeping u-second time,
* but we're assuming that this will not be a problem for the average user.
*/
#define MAX_RTC_COUNTER_VAL 0x00FFFFFF /**< Maximum value of the RTC counter. */
#define RTC_CLOCK_FREQ (32768 / (CFG_TIMER_PRESCALER + 1))
#define RTC_CLOCK_FREQ (uint32_t)(32768 / (CFG_TIMER_PRESCALER + 1))
#define RTC1_IRQ_PRI APP_IRQ_PRIORITY_LOW /**< Priority of the RTC1 interrupt (used for checking for timeouts and executing timeout handlers). */
#define MAX_RTC_TASKS_DELAY 47 /**< Maximum delay until an RTC task is executed. */
#define RTC_UNITS_TO_MICROSECONDS(RTC_UNITS) (((RTC_UNITS) * (uint64_t)1000000) / RTC_CLOCK_FREQ);
#define MICROSECONDS_TO_RTC_UNITS(MICROS) (((uint64_t)(MICROS) * RTC_CLOCK_FREQ) / 1000000)
static bool m_rtc1_running = false; /**< Boolean indicating if RTC1 is running. */
static bool us_ticker_inited = false;
@ -84,7 +98,7 @@ static void rtc1_start(uint32_t prescaler)
m_rtc1_running = true;
}
/**@brief Function for stopping the RTC1 timer.
/**@brief Function for stopping the RTC1 timer. We don't expect to call this.
*/
static void rtc1_stop(void)
{
@ -112,16 +126,10 @@ static void rtc1_stop(void)
*/
static __INLINE uint32_t rtc1_getCounter(void)
{
/* TODO: finish this review */
// uint32_t overflowed = 0;
// uint32_t counter = NRF_RTC1->COUNTER;
// if (NRF_RTC1->EVENTS_OVRFLW && (counter < MAX_RTC_COUNTER_VAL / 2)) {
// overflowed = (1 << 24);
// }
if (NRF_RTC1->EVENTS_OVRFLW) {
overflowBits += (1 << 24);
NRF_RTC1->EVENTS_OVRFLW = 0;
NRF_RTC1->EVTENCLR = RTC_EVTEN_OVRFLW_Msk;
}
return overflowBits | NRF_RTC1->COUNTER;
}
@ -135,38 +143,19 @@ void RTC1_IRQHandler(void)
if (NRF_RTC1->EVENTS_OVRFLW) {
overflowBits += (1 << 24);
NRF_RTC1->EVENTS_OVRFLW = 0;
NRF_RTC1->EVTENCLR = RTC_EVTEN_OVRFLW_Msk;
}
/* TODO review */
#define WINDOW 10000 /* 10ms window; hopefully all interrupt storms subside by then. */
if (NRF_RTC1->EVENTS_COMPARE[0] &&
us_ticker_callbackPending &&
(((int32_t)rtc1_getCounter() - (int32_t)us_ticker_callbackTimestamp) < WINDOW)) {
((int)(us_ticker_callbackTimestamp - rtc1_getCounter()) <= 0)) {
NRF_RTC1->EVENTS_COMPARE[0] = 0;
NRF_RTC1->EVTENCLR = RTC_EVTEN_COMPARE0_Msk;
us_ticker_callbackPending = false;
rtc1_disableCompareInterrupt();
us_ticker_irq_handler();
}
}
/**@brief Function for setting the RTC1 Capture Compare register 0, and enabling the corresponding
* event.
*
* @param[in] value New value of Capture Compare register 0.
*/
static __INLINE void rtc1_compare0_set(uint32_t value)
{
if (us_ticker_callbackPending) {
return;
}
NRF_RTC1->CC[0] = value & MAX_RTC_COUNTER_VAL;
rtc1_enableCompareInterrupt();
us_ticker_callbackTimestamp = value;
us_ticker_callbackPending = true;
}
void us_ticker_init(void)
{
if (us_ticker_inited) {
@ -186,7 +175,7 @@ uint32_t us_ticker_read()
/* Return a pseudo microsecond counter value. This is only as precise as the
* 32khz low-freq clock source, but could be adequate.*/
return ((rtc1_getCounter() * (uint64_t)1000000) / (uint32_t)APP_TIMER_CLOCK_FREQ);
return RTC_UNITS_TO_MICROSECONDS(rtc1_getCounter());
}
void us_ticker_set_interrupt(timestamp_t timestamp)
@ -199,8 +188,9 @@ void us_ticker_set_interrupt(timestamp_t timestamp)
return;
}
NRF_RTC1->CC[0] = timestamp & MAX_RTC_COUNTER_VAL;
us_ticker_callbackTimestamp = timestamp;
uint32_t callbackTime = MICROSECONDS_TO_RTC_UNITS(timestamp);
NRF_RTC1->CC[0] = callbackTime & MAX_RTC_COUNTER_VAL;
us_ticker_callbackTimestamp = callbackTime;
us_ticker_callbackPending = true;
rtc1_enableCompareInterrupt();
}