Fix for issue #7707 PwmOut inverted

since obj->sequence = &obj->pulse
and most significant bit of sequence denotes the polarity, we should set it.

Author: MateuszM

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/pwmout_api.c

@@ -57,6 +57,9 @@
 #define MAX_PWM_PERIOD_MS   (MAX_PWM_PERIOD_US / 1000)
 #define MAX_PWM_PERIOD_S    ((float) MAX_PWM_PERIOD_US / 1000000.0f)
 
+/* Sequence bit that denotes the polarity of the pwm waveform. */
+#define SEQ_POLARITY_BIT    (0x8000)
+
 /* Allocate PWM instances. */
 static nrf_drv_pwm_t nordic_nrf5_pwm_instance[] = {
 #if PWM0_ENABLED
@@ -140,7 +143,7 @@ void pwmout_init(pwmout_t *obj, PinName pin)
     /* Get hardware instance from pinmap. */
     int instance = pin_instance_pwm(pin);
 
-    MBED_ASSERT(instance < (int)(sizeof(nordic_nrf5_pwm_instance) / sizeof(nrf_drv_pwm_t)));
+    MBED_ASSERT(instance < (int) (sizeof(nordic_nrf5_pwm_instance) / sizeof(nrf_drv_pwm_t)));
 
     /* Populate PWM object with default values. */
     obj->instance = instance;
@@ -153,6 +156,9 @@ void pwmout_init(pwmout_t *obj, PinName pin)
     obj->sequence.repeats = 0;
     obj->sequence.end_delay = 0;
 
+    /* Set active low logic. */
+    obj->pulse |= SEQ_POLARITY_BIT;
+
     /* Initialize PWM instance. */
     nordic_pwm_init(obj);
 }
@@ -184,17 +190,20 @@ void pwmout_write(pwmout_t *obj, float percent)
     /* Find counts based on period. */
     uint16_t pulse = obj->period * percent;
 
+    /* Clear sequence, but keep the polarity bit */
+    obj->pulse &= SEQ_POLARITY_BIT;
+
     /* Ensure we don't overcount. */
-    obj->pulse = (pulse > MAX_PWM_COUNTERTOP) ? MAX_PWM_COUNTERTOP : pulse;
+    obj->pulse |= (pulse > MAX_PWM_COUNTERTOP) ? MAX_PWM_COUNTERTOP : pulse;
 
     /* Store actual percentage passed as parameter to avoid floating point rounding errors. */
     obj->percent = percent;
 
     /* Set new duty-cycle. */
     ret_code_t result = nrf_drv_pwm_simple_playback(&nordic_nrf5_pwm_instance[obj->instance],
-                                                    &obj->sequence,
-                                                    1,
-                                                    NRF_DRV_PWM_FLAG_LOOP);
+            &obj->sequence,
+            1,
+            NRF_DRV_PWM_FLAG_LOOP);
 
     MBED_ASSERT(result == NRF_SUCCESS);
 }
@@ -266,10 +275,11 @@ void pwmout_period_us(pwmout_t *obj, int period)
     }
 
     /* Scale new count based on stored duty-cycle and new period. */
-    uint32_t pulse = (period * obj->pulse) / obj->period;
+    uint32_t pulse = (period * (obj->pulse & ~SEQ_POLARITY_BIT)) / obj->period;
 
     /* Store new values in object. */
-    obj->pulse = pulse;
+    obj->pulse &= SEQ_POLARITY_BIT;
+    obj->pulse |= pulse;
     obj->period = period;
     obj->percent = (float) pulse / (float) period;
 
@@ -287,8 +297,9 @@ void pwmout_pulsewidth(pwmout_t *obj, float pulse)
     DEBUG_PRINTF("pwmout_pulsewidt: %f\r\n", pulse);
 
     /* Cap pulsewidth to period before setting it. */
-    if ((pulse * 1000000) > (float) obj->pulse) {
-        obj->pulse = obj->period;
+    if ((pulse * 1000000) > (float) (obj->pulse & ~SEQ_POLARITY_BIT)) {
+        obj->pulse &= SEQ_POLARITY_BIT;
+        obj->pulse |= obj->period;
         pwmout_pulsewidth_us(obj, obj->pulse);
     } else {
         pwmout_pulsewidth_us(obj, pulse * 1000000);
@@ -306,7 +317,8 @@ void pwmout_pulsewidth_ms(pwmout_t *obj, int pulse)
 
     /* Cap pulsewidth to period before setting it. */
     if ((pulse * 1000) > (int) obj->period) {
-        obj->pulse = obj->period;
+        obj->pulse &= SEQ_POLARITY_BIT;
+        obj->pulse |= obj->period;
         pwmout_pulsewidth_us(obj, obj->pulse);
     } else {
         pwmout_pulsewidth_us(obj, pulse * 1000);
@@ -328,7 +340,8 @@ void pwmout_pulsewidth_us(pwmout_t *obj, int pulse)
     }
 
     /* Store new values in object. */
-    obj->pulse = pulse;
+    obj->pulse &= SEQ_POLARITY_BIT;
+    obj->pulse |= pulse;
     obj->percent = (float) pulse / (float) obj->period;
 
     /* Restart instance with new values. */