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Merge pull request #133 from xiongyihui/master 

fix 16bit timer pwm output
pull/135/head
Bogdan Marinescu 2013-12-19 00:54:16 -08:00
parent b74e0c8b39 6501b16213
commit f56cbfa53e
1 changed files with 10 additions and 6 deletions
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16
libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/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);
@ -92,8 +90,6 @@ 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;
// 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);
pwmout_write (obj, 0); pwmout_write (obj, 0);
@ -141,12 +137,19 @@ 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; uint32_t period_ticks = (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 old_period_ticks = timer->MR3; uint32_t old_period_ticks = timer->MR3;
// for 16bit timer, set prescaler to avoid overflow
uint16_t high_period_ticks = period_ticks >> 16;
if ((high_period_ticks) && (timer == LPC_CT16B0 || timer == LPC_CT16B1)) {
timer->PR = high_period_ticks;
period_ticks /= (high_period_ticks + 1);
}
timer->TCR = TCR_RESET; timer->TCR = TCR_RESET;
timer->MR3 = period_ticks; timer->MR3 = period_ticks;
@ -169,13 +172,14 @@ 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) {
pwmout_period_us(obj, us); pwmout_period_us(obj, us);
t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
} }
uint32_t t_off = timer->MR3 - t_on; uint32_t t_off = timer->MR3 - t_on;
timer->MR[tid.mr] = t_off; timer->MR[tid.mr] = t_off;