djsundog/circuitpython
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

mimxrt1011: pwmout: Add prescaler, fix duty_cycle=65535

Browse Source
This commit is contained in:
Jeff Epler 2021-04-01 13:04:06 -05:00
parent 489163b74e
commit 89fc0298ce
2 changed files with 45 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
ports/mimxrt10xx/common-hal/pwmio/PWMOut.c
View File

@ -149,6 +149,21 @@ void pwmout_reset(void) {
#define PWM_SRC_CLK_FREQ CLOCK_GetFreq(kCLOCK_IpgClk)
static int calculate_pulse_count(uint32_t frequency, uint8_t *prescaler) {
if (frequency > PWM_SRC_CLK_FREQ/2) {
return 0;
}
for(int shift = 0; shift<8; shift++) {
int pulse_count = PWM_SRC_CLK_FREQ/(1<<shift)/frequency;
if (pulse_count >= 65535) {
continue;
}
*prescaler = shift;
return pulse_count;
}
return 0;
}
pwmout_result_t common_hal_pwmio_pwmout_construct(pwmio_pwmout_obj_t *self,
const mcu_pin_obj_t *pin,
uint16_t duty,
@ -196,18 +211,18 @@ pwmout_result_t common_hal_pwmio_pwmout_construct(pwmio_pwmout_obj_t *self,
// pwmConfig.reloadLogic = kPWM_ReloadPwmFullCycle;
pwmConfig.enableDebugMode = true;
self->pulse_count = calculate_pulse_count(frequency, &self->prescaler);
if (self->pulse_count == 0) {
return PWMOUT_INVALID_FREQUENCY;
}
pwmConfig.prescale = self->prescaler;
if (PWM_Init(self->pwm->pwm, self->pwm->submodule, &pwmConfig) == kStatus_Fail) {
return PWMOUT_INVALID_PIN;
}
if (frequency == 0 || frequency > PWM_SRC_CLK_FREQ/2) {
return PWMOUT_INVALID_FREQUENCY;
}
if (PWM_SRC_CLK_FREQ / frequency >= 65536) {
return PWMOUT_INVALID_FREQUENCY;
}
pwm_signal_param_t pwmSignal = {
.pwmChannel = self->pwm->channel,
.level = kPWM_HighTrue,
@ -228,7 +243,6 @@ pwmout_result_t common_hal_pwmio_pwmout_construct(pwmio_pwmout_obj_t *self,
PWM_StartTimer(self->pwm->pwm, 1 << self->pwm->submodule);
self->pulse_count = PWM_SRC_CLK_FREQ/frequency;
common_hal_pwmio_pwmout_set_duty_cycle(self, duty);
@ -253,7 +267,11 @@ void common_hal_pwmio_pwmout_set_duty_cycle(pwmio_pwmout_obj_t *self, uint16_t d
// * it works in integer percents
// * it can't set the "X" duty cycle
self->duty_cycle = duty;
self->duty_scaled = ((uint32_t)duty * self->pulse_count + self->pulse_count/2) / 65535;
if (duty == 65535) {
self->duty_scaled = self->pulse_count + 1;
} else {
self->duty_scaled = ((uint32_t)duty * self->pulse_count + self->pulse_count/2) / 65535;
}
switch (self->pwm->channel) {
case kPWM_PwmX:
self->pwm->pwm->SM[self->pwm->submodule].VAL0 = 0;
@ -271,27 +289,37 @@ void common_hal_pwmio_pwmout_set_duty_cycle(pwmio_pwmout_obj_t *self, uint16_t d
}
uint16_t common_hal_pwmio_pwmout_get_duty_cycle(pwmio_pwmout_obj_t *self) {
if (self->duty_cycle == 65535) {
return 65535;
}
return ((uint32_t)self->duty_scaled * 65535 + 65535/2) / self->pulse_count;
}
void common_hal_pwmio_pwmout_set_frequency(pwmio_pwmout_obj_t *self,
uint32_t frequency) {
if (frequency > PWM_SRC_CLK_FREQ/2) {
int pulse_count = calculate_pulse_count(frequency, &self->prescaler);
if (pulse_count == 0) {
mp_raise_ValueError(translate("Invalid PWM frequency"));
}
if (PWM_SRC_CLK_FREQ / frequency >= 65536) {
mp_raise_ValueError(translate("Invalid PWM frequency"));
}
self->pulse_count = pulse_count;
self->pulse_count = PWM_SRC_CLK_FREQ/frequency;
// a small glitch can occur when adjusting the prescaler, from the setting
// of CTRL just below to the setting of the Ldok register in
// set_duty_cycle.
uint32_t reg = self->pwm->pwm->SM[self->pwm->submodule].CTRL;
reg &= ~(PWM_CTRL_PRSC_MASK);
reg |= PWM_CTRL_PRSC(self->prescaler);
self->pwm->pwm->SM[self->pwm->submodule].CTRL = reg;
self->pwm->pwm->SM[self->pwm->submodule].VAL1 = self->pulse_count;
// we need to recalculate the duty cycle. As a side effect of this
common_hal_pwmio_pwmout_set_duty_cycle(self, self->duty_cycle);
}
uint32_t common_hal_pwmio_pwmout_get_frequency(pwmio_pwmout_obj_t *self) {
return PWM_SRC_CLK_FREQ/self->pulse_count;
return PWM_SRC_CLK_FREQ/self->pulse_count/(1 << self->prescaler);
}
bool common_hal_pwmio_pwmout_get_variable_frequency(pwmio_pwmout_obj_t *self) {

1
ports/mimxrt10xx/common-hal/pwmio/PWMOut.h
View File

@ -37,6 +37,7 @@ typedef struct {
const mcu_pin_obj_t *pin;
const mcu_pwm_obj_t *pwm;
bool variable_frequency;
uint8_t prescaler;
uint16_t duty_cycle, duty_scaled, pulse_count;
} pwmio_pwmout_obj_t;