atmel-samd: Fix sharing TCCs by statically storing the current period.

A previous fix improved the duty_cycle channel value computation by
removing the reliance on the PER register which gave old values. It
saved the period on the object but failed to set anything for reused
timers. So, this breaks it out into a separate array that can be
shared across all object regardless of whether it used a new or
existing timer.

Author: tannewt

atmel-samd/common-hal/pulseio/PWMOut.c

@@ -39,6 +39,7 @@
 #  define TCC_SIZES         { MREPEAT(TCC_INST_NUM, _TCC_SIZE, 0) }
 
 uint32_t target_timer_frequencies[TC_INST_NUM + TCC_INST_NUM];
+static uint32_t timer_periods[TC_INST_NUM + TCC_INST_NUM];
 uint8_t timer_refcount[TC_INST_NUM + TCC_INST_NUM];
 const uint16_t prescaler[8] = {1, 2, 4, 8, 16, 64, 256, 1024};
 
@@ -88,6 +89,10 @@ bool channel_ok(const pin_timer_t* t, uint8_t index) {
             t->is_tc;
 }
 
+static uint8_t timer_index(uint32_t base_timer_address) {
+    return (base_timer_address - ((uint32_t) TCC0)) / 0x400;
+}
+
 void common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
                                           const mcu_pin_obj_t* pin,
                                           uint16_t duty,
@@ -107,10 +112,10 @@ void common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
     uint16_t primary_timer_index = 0xff;
     uint16_t secondary_timer_index = 0xff;
     if (pin->primary_timer.tc != NULL) {
-        primary_timer_index = (((uint32_t) pin->primary_timer.tcc) - ((uint32_t) TCC0)) / 0x400;
+        primary_timer_index = timer_index((uint32_t) pin->primary_timer.tcc);
     }
     if (pin->secondary_timer.tc != NULL) {
-        secondary_timer_index = (((uint32_t) pin->secondary_timer.tcc) - ((uint32_t) TCC0)) / 0x400;
+        secondary_timer_index = timer_index((uint32_t) pin->secondary_timer.tcc);
     }
 
     // Figure out which timer we are using.
@@ -159,6 +164,7 @@ void common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
             mp_raise_RuntimeError("All timers in use");
             return;
         }
+
         uint8_t resolution = 0;
         if (t->is_tc) {
             resolution = 16;
@@ -177,7 +183,7 @@ void common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
                 break;
             }
         }
-        self->period = top;
+        timer_periods[index] = top;
         if (t->is_tc) {
             struct tc_config config_tc;
             tc_get_config_defaults(&config_tc);
@@ -258,11 +264,14 @@ extern void common_hal_pulseio_pwmout_deinit(pulseio_pwmout_obj_t* self) {
 
 extern void common_hal_pulseio_pwmout_set_duty_cycle(pulseio_pwmout_obj_t* self, uint16_t duty) {
     const pin_timer_t* t = self->timer;
+    uint8_t index;
     if (t->is_tc) {
-        uint16_t adjusted_duty = self->period * duty / 0xffff;
+        index = timer_index((uint32_t) self->timer->tc);
+        uint16_t adjusted_duty = timer_periods[index] * duty / 0xffff;
         tc_set_compare_value(&self->tc_instance, t->channel, adjusted_duty);
     } else {
-        uint32_t adjusted_duty = ((uint64_t) self->period) * duty / 0xffff;
+        index = timer_index((uint32_t) self->timer->tcc);
+        uint32_t adjusted_duty = ((uint64_t) timer_periods[index]) * duty / 0xffff;
         tcc_set_compare_value(&self->tcc_instance, t->channel, adjusted_duty);
     }
 }
@@ -274,7 +283,7 @@ uint16_t common_hal_pulseio_pwmout_get_duty_cycle(pulseio_pwmout_obj_t* self) {
             /* Wait for sync */
         }
         uint16_t cv = t->tc->COUNT16.CC[t->channel].reg;
-        return cv * 0xffff / self->period;
+        return cv * 0xffff / timer_periods[timer_index((uint32_t) self->timer->tc)];
     } else {
         uint32_t cv = 0;
         if ((t->tcc->STATUS.vec.CCBV & (1 << t->channel)) != 0) {
@@ -283,7 +292,7 @@ uint16_t common_hal_pulseio_pwmout_get_duty_cycle(pulseio_pwmout_obj_t* self) {
             cv = t->tcc->CC[t->channel].reg;
         }
 
-        uint32_t duty_cycle = ((uint64_t) cv) * 0xffff / self->period;
+        uint32_t duty_cycle = ((uint64_t) cv) * 0xffff / timer_periods[timer_index((uint32_t) self->timer->tcc)];
 
         return duty_cycle;
     }
@@ -313,9 +322,12 @@ void common_hal_pulseio_pwmout_set_frequency(pulseio_pwmout_obj_t* self,
     }
     uint16_t old_duty = common_hal_pulseio_pwmout_get_duty_cycle(self);
     uint8_t old_divisor;
+    uint8_t index;
     if (t->is_tc) {
+        index = timer_index((uint32_t) self->timer->tc);
         old_divisor = t->tc->COUNT16.CTRLA.bit.PRESCALER;
     } else {
+        index = timer_index((uint32_t) self->timer->tcc);
         old_divisor = t->tcc->CTRLA.bit.PRESCALER;
     }
     if (new_divisor != old_divisor) {
@@ -329,7 +341,7 @@ void common_hal_pulseio_pwmout_set_frequency(pulseio_pwmout_obj_t* self,
             tcc_enable(&self->tcc_instance);
         }
     }
-    self->period = new_top;
+    timer_periods[index] = new_top;
     if (t->is_tc) {
         while (tc_is_syncing(&self->tc_instance)) {
             /* Wait for sync */
@@ -345,18 +357,16 @@ void common_hal_pulseio_pwmout_set_frequency(pulseio_pwmout_obj_t* self,
 uint32_t common_hal_pulseio_pwmout_get_frequency(pulseio_pwmout_obj_t* self) {
     uint32_t system_clock = system_cpu_clock_get_hz();
     const pin_timer_t* t = self->timer;
-    uint32_t top;
+    uint8_t index;
     uint8_t divisor;
     if (t->is_tc) {
-        top = t->tc->COUNT16.CC[0].reg;
+        index = timer_index((uint32_t) self->timer->tc);
         divisor = t->tc->COUNT16.CTRLA.bit.PRESCALER;
     } else {
-        top = t->tcc->PER.reg;
-        if (t->tcc->STATUS.bit.PERBV) {
-            top = t->tcc->PERB.reg;
-        }
+        index = timer_index((uint32_t) self->timer->tcc);
         divisor = t->tcc->CTRLA.bit.PRESCALER;
     }
+    uint32_t top = timer_periods[index];
     return (system_clock / prescaler[divisor]) / (top + 1);
 }
 

atmel-samd/common-hal/pulseio/PWMOut.h

@@ -38,7 +38,6 @@ typedef struct {
     const mcu_pin_obj_t *pin;
     const pin_timer_t* timer;
     bool variable_frequency;
-    uint32_t period;
     union {
         struct tc_module tc_instance;
         struct tcc_module tcc_instance;