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[LPC1347] Fix PwmOut prescaler for 16-bit timer 

* Fix PwmOut prescaler for 16-bit timer
* Remove static variable pwm_clock_mhz
* Fix spike pulse issue when 0% duty
pull/2810/head
Toyomasa Watarai 2016-09-26 16:06:01 +09:00
parent 196584d571
commit ec406b1740
1 changed files with 18 additions and 5 deletions
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23
hal/targets/hal/TARGET_NXP/TARGET_LPC13XX/pwmout_api.c
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@ -66,8 +66,6 @@ static LPC_CTxxBx_Type *Timers[4] = {
LPC_CT32B0, LPC_CT32B1 LPC_CT32B0, LPC_CT32B1
}; };
static unsigned int pwm_clock_mhz;
void pwmout_init(pwmout_t* obj, PinName pin) { void pwmout_init(pwmout_t* obj, PinName pin) {
// determine the channel // determine the channel
PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM); PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
@ -91,7 +89,12 @@ void pwmout_init(pwmout_t* obj, PinName pin) {
/* Reset Functionality on MR3 controlling the PWM period */ /* Reset Functionality on MR3 controlling the PWM period */
timer->MCR = 1 << 10; timer->MCR = 1 << 10;
pwm_clock_mhz = SystemCoreClock / 1000000; if (timer == LPC_CT16B0 || timer == LPC_CT16B1) {
/* Set 16-bit timer prescaler to avoid timer expire for default 20ms
This can be also modified by user application, but the prescaler value
might be trade-off to timer accuracy */
timer->PR = 30;
}
// default to 20ms: standard for servos, and fine for e.g. brightness control // default to 20ms: standard for servos, and fine for e.g. brightness control
pwmout_period_ms(obj, 20); pwmout_period_ms(obj, 20);
@ -116,7 +119,14 @@ void pwmout_write(pwmout_t* obj, float value) {
LPC_CTxxBx_Type *timer = Timers[tid.timer]; LPC_CTxxBx_Type *timer = Timers[tid.timer];
uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value); uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
// to avoid spike pulse when duty is 0%
if (value == 0) {
t_off++;
}
timer->TCR = TCR_RESET;
timer->MR[tid.mr] = t_off; timer->MR[tid.mr] = t_off;
timer->TCR = TCR_CNT_EN;
} }
float pwmout_read(pwmout_t* obj) { float pwmout_read(pwmout_t* obj) {
@ -124,6 +134,9 @@ float pwmout_read(pwmout_t* obj) {
LPC_CTxxBx_Type *timer = Timers[tid.timer]; LPC_CTxxBx_Type *timer = Timers[tid.timer];
float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3); float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
if (timer->MR[tid.mr] > timer->MR3) {
v = 0.0f;
}
return (v > 1.0f) ? (1.0f) : (v); return (v > 1.0f) ? (1.0f) : (v);
} }
@ -138,11 +151,11 @@ void pwmout_period_ms(pwmout_t* obj, int ms) {
// Set the PWM period, keeping the duty cycle the same. // Set the PWM period, keeping the duty cycle the same.
void pwmout_period_us(pwmout_t* obj, int us) { void pwmout_period_us(pwmout_t* obj, int us) {
int i = 0; int i = 0;
uint32_t period_ticks = pwm_clock_mhz * us;
timer_mr tid = pwm_timer_map[obj->pwm]; timer_mr tid = pwm_timer_map[obj->pwm];
LPC_CTxxBx_Type *timer = Timers[tid.timer]; LPC_CTxxBx_Type *timer = Timers[tid.timer];
uint32_t old_period_ticks = timer->MR3; uint32_t old_period_ticks = timer->MR3;
uint32_t period_ticks = (SystemCoreClock / 1000000 * us) / (timer->PR + 1);
timer->TCR = TCR_RESET; timer->TCR = TCR_RESET;
timer->MR3 = period_ticks; timer->MR3 = period_ticks;
@ -166,9 +179,9 @@ void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
} }
void pwmout_pulsewidth_us(pwmout_t* obj, int us) { void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
uint32_t t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
timer_mr tid = pwm_timer_map[obj->pwm]; timer_mr tid = pwm_timer_map[obj->pwm];
LPC_CTxxBx_Type *timer = Timers[tid.timer]; LPC_CTxxBx_Type *timer = Timers[tid.timer];
uint32_t t_on = (uint32_t)((((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) / (timer->PR + 1));
timer->TCR = TCR_RESET; timer->TCR = TCR_RESET;
if (t_on > timer->MR3) { if (t_on > timer->MR3) {