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[LPC11U68, LPC1549] Fixed PwmOut SCT Bugs 

* Fixed period & pulse-width off-by-one errors
* Fixed 0% duty cycle output
* Improved duty cycle resolution at high frequencies
pull/1512/head
neilt6 2016-01-21 09:30:14 -07:00
parent 813874ee2b
commit 132f1e75a5
2 changed files with 62 additions and 42 deletions
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53
libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/pwmout_api.c
View File

@ -83,10 +83,6 @@ void pwmout_init(pwmout_t* obj, PinName pin) {
// halt and clear the counter
pwm->CTRL |= (1 << 2) | (1 << 3);
// System Clock -> us_ticker (1)MHz
pwm->CTRL &= ~(0x7F << 5);
pwm->CTRL |= (((SystemCoreClock/1000000 - 1) & 0x7F) << 5);
switch(pwm_mapped) {
case SCT0_0:
case SCT1_0:
@ -117,14 +113,6 @@ void pwmout_init(pwmout_t* obj, PinName pin) {
// Event 1 : MATCH and MATCHSEL=1
pwm->EV1_CTRL = (1 << 12) | (1 << 0);
pwm->EV1_STATE = 0xFFFFFFFF;
// Match reload register
pwm->MATCHREL0 = 20000; // 20ms
pwm->MATCHREL1 = (pwm->MATCHREL0 / 4); // 50% duty
// unhalt the counter:
// - clearing bit 2 of the CTRL register
pwm->CTRL &= ~(1 << 2);
// default to 20ms: standard for servos, and fine for e.g. brightness control
pwmout_period_ms(obj, 20);
@ -140,18 +128,25 @@ void pwmout_free(pwmout_t* obj) {
}
void pwmout_write(pwmout_t* obj, float value) {
LPC_SCT0_Type* pwm = obj->pwm;
if (value < 0.0f) {
value = 0.0;
} else if (value > 1.0f) {
value = 1.0;
}
uint32_t t_on = (uint32_t)((float)(obj->pwm->MATCHREL0) * value);
obj->pwm->MATCHREL1 = t_on;
uint32_t t_on = (uint32_t)((float)(pwm->MATCHREL0 + 1) * value);
if (t_on > 0) {
pwm->MATCHREL1 = t_on - 1;
pwm->CTRL &= ~(1 << 2);
} else {
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}
float pwmout_read(pwmout_t* obj) {
uint32_t t_off = obj->pwm->MATCHREL0;
uint32_t t_on = obj->pwm->MATCHREL1;
uint32_t t_off = obj->pwm->MATCHREL0 + 1;
uint32_t t_on = obj->pwm->MATCHREL1 + 1;
float v = (float)t_on/(float)t_off;
return (v > 1.0f) ? (1.0f) : (v);
}
@ -166,11 +161,20 @@ 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) {
uint32_t t_off = obj->pwm->MATCHREL0;
uint32_t t_on = obj->pwm->MATCHREL1;
LPC_SCT0_Type* pwm = obj->pwm;
uint32_t t_off = pwm->MATCHREL0 + 1;
uint32_t t_on = pwm->MATCHREL1 + 1;
float v = (float)t_on/(float)t_off;
obj->pwm->MATCHREL0 = (uint32_t)us;
obj->pwm->MATCHREL1 = (uint32_t)((float)us * (float)v);
uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
uint32_t pulsewidth_ticks = period_ticks * v;
pwm->MATCHREL0 = period_ticks - 1;
if (pulsewidth_ticks > 0) {
pwm->MATCHREL1 = pulsewidth_ticks - 1;
pwm->CTRL &= ~(1 << 2);
} else {
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}
void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
@ -182,7 +186,14 @@ void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
}
void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
obj->pwm->MATCHREL1 = (uint32_t)us;
LPC_SCT0_Type* pwm = obj->pwm;
if (us > 0) {
pwm->MATCHREL1 = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) - 1;
pwm->CTRL &= ~(1 << 2);
} else {
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}
#endif

51
libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/pwmout_api.c
View File

@ -89,14 +89,6 @@ void pwmout_init(pwmout_t* obj, PinName pin) {
// halt and clear the counter
pwm->CTRL |= (1 << 2) | (1 << 3);
// System Clock -> us_ticker (1)MHz
pwm->CTRL &= ~(0x7F << 5);
pwm->CTRL |= (((SystemCoreClock/1000000 - 1) & 0x7F) << 5);
// Match reload register
pwm->MATCHREL0 = 20000; // 20ms
pwm->MATCHREL1 = (pwm->MATCHREL0 / 4); // 50% duty
pwm->OUT0_SET = (1 << 0); // event 0
pwm->OUT0_CLR = (1 << 1); // event 1
@ -105,10 +97,6 @@ void pwmout_init(pwmout_t* obj, PinName pin) {
pwm->EV1_CTRL = (1 << 12) | (1 << 0);
pwm->EV1_STATE = 0xFFFFFFFF;
// unhalt the counter:
// - clearing bit 2 of the CTRL register
pwm->CTRL &= ~(1 << 2);
// default to 20ms: standard for servos, and fine for e.g. brightness control
pwmout_period_ms(obj, 20);
pwmout_write (obj, 0);
@ -127,13 +115,19 @@ void pwmout_write(pwmout_t* obj, float value) {
} else if (value > 1.0f) {
value = 1.0;
}
uint32_t t_on = (uint32_t)((float)(pwm->MATCHREL0) * value);
pwm->MATCHREL1 = t_on;
uint32_t t_on = (uint32_t)((float)(pwm->MATCHREL0 + 1) * value);
if (t_on > 0) {
pwm->MATCHREL1 = t_on - 1;
pwm->CTRL &= ~(1 << 2);
} else {
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}
float pwmout_read(pwmout_t* obj) {
uint32_t t_off = obj->pwm->MATCHREL0;
uint32_t t_on = obj->pwm->MATCHREL1;
uint32_t t_off = obj->pwm->MATCHREL0 + 1;
uint32_t t_on = obj->pwm->MATCHREL1 + 1;
float v = (float)t_on/(float)t_off;
return (v > 1.0f) ? (1.0f) : (v);
}
@ -149,11 +143,19 @@ 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) {
LPC_SCT0_Type* pwm = obj->pwm;
uint32_t t_off = pwm->MATCHREL0;
uint32_t t_on = pwm->MATCHREL1;
uint32_t t_off = pwm->MATCHREL0 + 1;
uint32_t t_on = pwm->MATCHREL1 + 1;
float v = (float)t_on/(float)t_off;
pwm->MATCHREL0 = (uint32_t)us;
pwm->MATCHREL1 = (uint32_t)((float)us * (float)v);
uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
uint32_t pulsewidth_ticks = period_ticks * v;
pwm->MATCHREL0 = period_ticks - 1;
if (pulsewidth_ticks > 0) {
pwm->MATCHREL1 = pulsewidth_ticks - 1;
pwm->CTRL &= ~(1 << 2);
} else {
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}
void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
@ -165,6 +167,13 @@ void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
}
void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
obj->pwm->MATCHREL1 = (uint32_t)us;
LPC_SCT0_Type* pwm = obj->pwm;
if (us > 0) {
pwm->MATCHREL1 = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) - 1;
pwm->CTRL &= ~(1 << 2);
} else {
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}