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Extend range of PWM and minor code optimisations 

Corrected minor bug that prevented the use of long periods (beyond 500ms).
Updated timer instance to be const to allow compiler optimisation
minor code cleanups
master microbit_hfclk+mb6
Joe Finney 2016-10-24 15:56:05 +01:00
parent be51bd33c1
commit 03f4fbc253
1 changed files with 6 additions and 8 deletions
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14
targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/pwmout_api.c
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@ -31,7 +31,7 @@
#define TIMER_PRESCALER_MIN 4
#define TIMER_PRESCALER_MAX 9
static NRF_TIMER_Type *timer = NRF_TIMER2;
static NRF_TIMER_Type* const timer = NRF_TIMER2;
// PWM levels, both in absolute microseconds, and TIMER ticks (we cache both for simplicity and performance).
static uint32_t pwm_us[PWM_CHANNELS] = {0};
@ -66,13 +66,10 @@ void TIMER2_IRQHandler(void)
// Disable this interrupt - it is needed only when PWM values change.
timer->SHORTS = TIMER_SHORTS_COMPARE3_CLEAR_Msk;
timer->INTENCLR = TIMER_INTENCLR_COMPARE3_Msk;
timer->PRESCALER = pwm_prescaler;
timer->CC[TIMER_PERIOD_CC] = pwm_period_ticks;
timer->TASKS_START = 1;
timer->EVENTS_COMPARE[TIMER_PERIOD_CC] = 0;
}
#ifdef __cplusplus
@ -270,6 +267,7 @@ void pwmout_period_us(pwmout_t *obj, int us)
{
uint32_t p = 0x10000;
int prescaler = TIMER_PRESCALER_MIN;
uint32_t old_period_us = pwm_period_us;
// Quick validation - do nothing if the frequency is identical to it's current value.
if (us == pwm_period_us)
@ -288,6 +286,7 @@ void pwmout_period_us(pwmout_t *obj, int us)
// Update global frequency timestamps.
pwm_prescaler = prescaler;
pwm_period_us = us;
pwm_period_ticks = PWM_US_TO_TICKS(us);
pwmout_t pwm;
@ -296,15 +295,14 @@ void pwmout_period_us(pwmout_t *obj, int us)
// Update all PWM channel values to maintin the same duty cycle (mbed standard behaviour).
for (int i=0; i<PWM_CHANNELS; i++)
{
if (pwm_ticks[i] != PWM_VALUE_INVALID)
{
pwm.pin = pwm_pins[i];
pwmout_pulsewidth_us(&pwm, (uint32_t) ((float)pwm_us[i] * ((float)us / (float)pwm_period_us)));
pwmout_pulsewidth_us(&pwm, (uint32_t) ((float)pwm_us[i] * ((float)us / (float)old_period_us)));
pwm.pin = NC;
}
// cache our new period in microseconds for later use
pwm_period_us = us;
}
}
void pwmout_pulsewidth(pwmout_t *obj, float seconds)