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cpu/efm32: improve PWM driver #22665

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Merged
crasbe merged 2 commits into from
Sep 6, 2026
+14 −3
Merged

cpu/efm32: improve PWM driver #22665

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ef8634c
cpu/efm32: add support for PWM center mode
basilfx Sep 5, 2026
5edac95
cpu/efm32: fix PWM_RIGHT being inverted
basilfx Sep 5, 2026
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2 changes: 1 addition & 1 deletion cpu/efm32/include/periph_cpu.h
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Original file line number Diff line number Diff line change
Expand Up @@ -455,7 +455,7 @@ typedef struct {
typedef enum {
PWM_LEFT = timerModeUp, /**< use left aligned PWM */
PWM_RIGHT = timerModeDown, /**< use right aligned PWM */
PWM_CENTER = timerModeUp /**< not supported, use left aligned */
PWM_CENTER = timerModeUpDown /**< use center aligned PWM */
} pwm_mode_t;
/** @} */
#endif /* ndef DOXYGEN */
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15 changes: 13 additions & 2 deletions cpu/efm32/periph/pwm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,9 +37,12 @@ uint32_t pwm_init(pwm_t dev, pwm_mode_t mode, uint32_t freq, uint16_t res)
CMU_ClockEnable(cmuClock_HFPER, true);
CMU_ClockEnable(pwm_config[dev].cmu, true);

/* in up/down counting mode a full period takes twice the number of ticks */
uint32_t ticks = (mode == PWM_CENTER) ? ((uint32_t)res * 2) : (uint32_t)res;

/* calculate the prescaler by determining the best prescaler */
uint32_t freq_timer = CMU_ClockFreqGet(pwm_config[dev].cmu);
TIMER_Prescale_TypeDef prescaler = TIMER_PrescalerCalc(freq * res,
TIMER_Prescale_TypeDef prescaler = TIMER_PrescalerCalc(freq * ticks,
freq_timer);

if (prescaler > timerPrescale1024) {
Expand All @@ -62,6 +65,14 @@ uint32_t pwm_init(pwm_t dev, pwm_mode_t mode, uint32_t freq, uint16_t res)

init_channel.mode = timerCCModePWM;

if (mode == PWM_RIGHT) {
/* down counting sets the output at the start of the period and clears
* it on compare match, so the output has to be inverted to obtain a
* right aligned pulse with the requested duty cycle. */
init_channel.coist = true;
init_channel.outInvert = true;
}

for (int i = 0; i < pwm_config[dev].channels; i++) {
pwm_chan_conf_t channel = pwm_config[dev].channel[i];

Expand All @@ -84,7 +95,7 @@ uint32_t pwm_init(pwm_t dev, pwm_mode_t mode, uint32_t freq, uint16_t res)
/* enable peripheral */
TIMER_Enable(pwm_config[dev].dev, true);

return freq_timer / TIMER_Prescaler2Div(prescaler) / res;
return freq_timer / TIMER_Prescaler2Div(prescaler) / ticks;
}

uint8_t pwm_channels(pwm_t dev)
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