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pull/932/head
Rohit Grover 2015-02-24 13:56:42 +00:00
parent 5906372a58
commit 8c21ef208c
1 changed files with 19 additions and 15 deletions
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34
libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/us_ticker.c
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@ -22,16 +22,16 @@
#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.
*/
/*
* 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 (uint32_t)(32768 / (CFG_TIMER_PRESCALER + 1))
@ -71,7 +71,8 @@ static __INLINE void rtc1_disableOverflowInterrupt(void)
NRF_RTC1->EVTENCLR = RTC_EVTEN_OVRFLW_Msk;
}
/**@brief Function for starting the RTC1 timer. The RTC timer is expected to
/**
* @brief Function for starting the RTC1 timer. The RTC timer is expected to
* keep running--some interrupts may be disabled temporarily.
*
* @param[in] prescaler Value of the RTC1 PRESCALER register. Set to 0 for no prescaling.
@ -90,7 +91,8 @@ static void rtc1_start(uint32_t prescaler)
nrf_delay_us(MAX_RTC_TASKS_DELAY);
}
/**@brief Function for stopping the RTC1 timer. We don't expect to call this.
/**
* @brief Function for stopping the RTC1 timer. We don't expect to call this.
*/
void rtc1_stop(void)
{
@ -106,7 +108,8 @@ void rtc1_stop(void)
}
/**@brief Function for returning the current value of the RTC1 counter.
/**
* @brief Function for returning the current value of the RTC1 counter.
*
* @return Current RTC1 counter as a 32-bit value (even though the underlying counter is 24-bit)
*/
@ -120,7 +123,8 @@ static __INLINE uint32_t rtc1_getCounter(void)
return overflowBits | NRF_RTC1->COUNTER;
}
/**@brief Function for handling the RTC1 interrupt.
/**
* @brief Function for handling the RTC1 interrupt.
*
* @details Checks for timeouts, and executes timeout handlers for expired timers.
*/
@ -190,6 +194,6 @@ void us_ticker_disable_interrupt(void)
void us_ticker_clear_interrupt(void)
{
NRF_RTC1->EVENTS_OVRFLW = 0;
NRF_RTC1->EVENTS_OVRFLW = 0;
NRF_RTC1->EVENTS_COMPARE[0] = 0;
}