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[LPC824] Add more comments for PwmOut fix

pull/1585/head
Toyomasa Watarai 2016-03-04 16:00:32 +09:00
parent 6ab159af26
commit a86504d205
1 changed files with 19 additions and 8 deletions
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27
libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC82X/pwmout_api.c
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@ -120,16 +120,21 @@ void pwmout_write(pwmout_t* obj, float value)
value = 1.0f;
}
uint32_t t_on = (uint32_t)((float)(obj->pwm->MATCHREL[obj->pwm_ch * 2] + 1) * value);
if (t_on > 0) {
if (value != 1.0f) {
if (t_on > 0) { // duty is not 0%
if (value != 1.0f) { // duty is not 100%
obj->pwm->MATCHREL[(obj->pwm_ch * 2) + 1] = t_on - 1;
// unhalt the counter
obj->pwm->CTRL &= ~(1 << 2);
} else {
} else { // duty is 100%
// halt and clear the counter
obj->pwm->CTRL |= (1 << 2) | (1 << 3);
// output level tied to high
obj->pwm->OUTPUT |= (1 << obj->pwm_ch);
}
} else {
} else { // duty is 0%
// halt and clear the counter
obj->pwm->CTRL |= (1 << 2) | (1 << 3);
// output level tied to low
obj->pwm->OUTPUT &= ~(1 << obj->pwm_ch);
}
}
@ -155,15 +160,19 @@ void pwmout_period_ms(pwmout_t* obj, int ms)
// Set the PWM period, keeping the duty cycle the same.
void pwmout_period_us(pwmout_t* obj, int us)
{
// The period are off by one for MATCHREL, so +1 to get actual value
uint32_t t_off = obj->pwm->MATCHREL[(obj->pwm_ch * 2) + 0] + 1;
uint32_t t_on = obj->pwm->MATCHREL[(obj->pwm_ch * 2) + 1] + 1;
float v = (float)t_on/(float)t_off;
obj->pwm->MATCHREL[(obj->pwm_ch * 2) + 0] = (uint32_t)us - 1;
if (us > 0) {
if (us > 0) { // PWM period is not 0
obj->pwm->MATCHREL[(obj->pwm_ch * 2) + 1] = (uint32_t)((float)us * (float)v) - 1;
// unhalt the counter
obj->pwm->CTRL &= ~(1 << 2);
} else {
} else { // PWM period is 0
// halt and clear the counter
obj->pwm->CTRL |= (1 << 2) | (1 << 3);
// output level tied to low
obj->pwm->OUTPUT &= ~(1 << obj->pwm_ch);
}
}
@ -180,11 +189,13 @@ void pwmout_pulsewidth_ms(pwmout_t* obj, int ms)
void pwmout_pulsewidth_us(pwmout_t* obj, int us)
{
if (us > 0) {
if (us > 0) { // PWM peried is not 0
obj->pwm->MATCHREL[(obj->pwm_ch * 2) + 1] = (uint32_t)us - 1;
obj->pwm->CTRL &= ~(1 << 2);
} else {
} else { //PWM period is 0
// halt and clear the counter
obj->pwm->CTRL |= (1 << 2) | (1 << 3);
// output level tied to low
obj->pwm->OUTPUT &= ~(1 << obj->pwm_ch);
}
}