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[LPC812] Fixed PwmOut SCT bugs #1656

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Merged
merged 2 commits into from
Apr 8, 2016
Merged

[LPC812] Fixed PwmOut SCT bugs #1656

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109f93f
[LPC812] Fixed PwmOut SCT bugs
toyowata Apr 8, 2016
b7942a7
[LPC812] Fix incorrect duty cycle
toyowata Apr 8, 2016
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54 changes: 34 additions & 20 deletions libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/pwmout_api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,6 @@ static int get_available_sct() {
// Find available output channel 0..3
// Also need one Match register per channel
for (i = 0; i < CONFIG_SCT_nOU; i++) {
// for (i = 0; i < 4; i++) {
if ((sct_used & (1 << i)) == 0)
return i;
}
Expand All @@ -47,7 +46,7 @@ static int get_available_sct() {
// Any Port pin may be used for PWM.
// Max number of PWM outputs is 4
void pwmout_init(pwmout_t* obj, PinName pin) {
MBED_ASSERT(pin != (uint32_t)NC);
MBED_ASSERT(pin != (PinName)NC);

int sct_n = get_available_sct();
if (sct_n == -1) {
Expand All @@ -72,8 +71,6 @@ void pwmout_init(pwmout_t* obj, PinName pin) {
LPC_SYSCON->PRESETCTRL |= (1 << 8);

// Two 16-bit counters, autolimit (ie reset on Match_0)
//pwm->CONFIG &= ~(0x1);
//pwm->CONFIG |= (1 << 17);
pwm->CONFIG |= ((0x3 << 17) | 0x01);

// halt and clear the counter
Expand All @@ -90,9 +87,6 @@ void pwmout_init(pwmout_t* obj, PinName pin) {
// - clearing bit 2 of the CTRL register
pwm->CTRL_U &= ~(1 << 2);

// Not using IRQs
//NVIC_SetVector(PWM_IRQn, (uint32_t)pwm_irq_handler);
//NVIC_EnableIRQ(PWM_IRQn);
}

// LPC81x has only one SCT and 4 Outputs
Expand Down Expand Up @@ -157,6 +151,14 @@ void pwmout_write(pwmout_t* obj, float value) {
// Match_0 is PWM period. Compute new endtime of pulse for current channel
uint32_t t_off = (uint32_t)((float)(obj->pwm->MATCHREL[0].U) * value);
obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = t_off; // New endtime

if (value == 0.0f) { // duty is 0%
// Set CLR event to be same as SET event, makes output to be 0 (low)
obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << 0);
} else {
// Use normal CLR event (current SCT ch + 1)
obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << ((obj->pwm_ch) + 1));
}
}

// Get dutycycle (0.0 .. 1.0)
Expand Down Expand Up @@ -190,20 +192,26 @@ void pwmout_period_us(pwmout_t* obj, int us) {
uint32_t t_period = obj->pwm->MATCHREL[0].U; // Current PWM period
obj->pwm->MATCHREL[0].U = (uint32_t)us; // New PWM period

//Keep the dutycycle for the new PWM period
//Should really do this for all active channels!!
//This problem exists in all mbed libs.

//Sanity check
// Sanity check
if (t_period == 0) {
return;
// obj->pwm->MATCHREL[(obj->pwm_ch) + 1].L = 0; // New endtime for this channel
return;
}
else {
int cnt = sct_used;
int ch = 0;
// Update match period for exising PWM channels
do {
// Get current pulse width
uint32_t t_off = obj->pwm->MATCHREL[ch + 1].U;
// Get the duty
float v = (float)t_off/(float)t_period;
// Update pulse width for this channel
obj->pwm->MATCHREL[ch + 1].U = (uint32_t)((float)us * (float)v);
// Get next used SCT channel
cnt = cnt >> 1;
ch++;
} while (cnt != 0);
}
else {
uint32_t t_off = obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U;
float v = (float)t_off/(float)t_period;
obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = (uint32_t)((float)us * (float)v); // New endtime for this channel
}
}


Expand All @@ -219,7 +227,13 @@ void pwmout_pulsewidth_ms(pwmout_t* obj, int ms){

//Set pulsewidth
void pwmout_pulsewidth_us(pwmout_t* obj, int us) {

if (us == 0) { // pulse width is 0
// Set CLR event to be same as SET event, makes output to be 0 (low)
obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << 0);
} else {
// Use normal CLR event (current SCT ch + 1)
obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << ((obj->pwm_ch) + 1));
}
//Should add Sanity check to make sure pulsewidth < period!
obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = (uint32_t)us; // New endtime for this channel
}
Expand Down