Avoid glitches on repeated analogWrite() PWM

GrumpyOldPizza · Aug 12, 2018 · 1c9e497 · 1c9e497
1 parent a42d1e1
commit 1c9e497
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Showing 2 changed files with 44 additions and 24 deletions.
diff --git a/cores/arduino/wiring_analog.c b/cores/arduino/wiring_analog.c
@@ -39,6 +39,7 @@ static stm32l0_timer_t stm32l0_pwm[PWM_INSTANCE_COUNT];
 
 static uint8_t _channels[PWM_INSTANCE_COUNT];
 static int _readResolution = 10;
+static int _readPeriod = 2000;
 static int _writeResolution = 8;
 
 void analogReference(eAnalogReference reference)
@@ -51,6 +52,11 @@ void analogReadResolution(int resolution)
     _readResolution = resolution;
 }
 
+void analogReadPeriod(int period)
+{
+    _readPeriod = period;
+}
+
 static inline uint32_t mapResolution(uint32_t value, uint32_t from, uint32_t to)
 {
     if (from == to)
@@ -99,7 +105,7 @@ uint32_t __analogReadInternal(uint32_t channel, uint32_t smp)
 	}
 	else
 	{
-	  return 0;
+	    return 0;
 	}
     }
 }
@@ -125,7 +131,7 @@ uint32_t analogRead(uint32_t ulPin)
 
     stm32l0_gpio_pin_configure(g_APinDescription[ulPin].pin, (STM32L0_GPIO_PUPD_NONE | STM32L0_GPIO_MODE_ANALOG));
 
-    input = __analogReadInternal(g_APinDescription[ulPin].adc_channel, 2000);
+    input = __analogReadInternal(g_APinDescription[ulPin].adc_channel, _readPeriod);
 
     return mapResolution(input, 12, _readResolution);
 }
@@ -160,33 +166,40 @@ void analogWrite(uint32_t ulPin, uint32_t value)
     {
 	instance = g_APinDescription[ulPin].pwm_instance;
 
-	if (stm32l0_pwm[instance].state == STM32L0_TIMER_STATE_NONE)
+	if (_channels[instance] & (1u << g_APinDescription[ulPin].pwm_channel))
 	{
-	    stm32l0_timer_create(&stm32l0_pwm[instance], g_PWMInstances[instance], STM32L0_PWM_IRQ_PRIORITY, 0);
+	    stm32l0_timer_compare(&stm32l0_pwm[instance], g_APinDescription[ulPin].pwm_channel, mapResolution(value, _writeResolution, 12));
 	}
-
-	if (stm32l0_pwm[instance].state == STM32L0_TIMER_STATE_INIT)
+	else
 	{
-	    carrier = 2000000;
-	    modulus = 4095;
-
-	    divider = stm32l0_timer_clock(&stm32l0_pwm[instance]) / carrier;
+	    _channels[instance] |= (1u << g_APinDescription[ulPin].pwm_channel);
+
+	    if (stm32l0_pwm[instance].state == STM32L0_TIMER_STATE_NONE)
+	    {
+		stm32l0_timer_create(&stm32l0_pwm[instance], g_PWMInstances[instance], STM32L0_PWM_IRQ_PRIORITY, 0);
+	    }
 
-	    if (divider == 0)
+	    if (stm32l0_pwm[instance].state == STM32L0_TIMER_STATE_INIT)
 	    {
-		divider = 1;
+		carrier = 2000000;
+		modulus = 4095;
+
+		divider = stm32l0_timer_clock(&stm32l0_pwm[instance]) / carrier;
+
+		if (divider == 0)
+		{
+		    divider = 1;
+		}
+
+		stm32l0_timer_enable(&stm32l0_pwm[instance], divider -1, 0, NULL, NULL, 0);
+		stm32l0_timer_start(&stm32l0_pwm[instance], modulus -1, false);
 	    }
 
-	    stm32l0_timer_enable(&stm32l0_pwm[instance], divider -1, 0, NULL, NULL, 0);
-	    stm32l0_timer_start(&stm32l0_pwm[instance], modulus -1, false);
+	    stm32l0_gpio_pin_configure(g_APinDescription[ulPin].pin, (STM32L0_GPIO_PUPD_NONE | STM32L0_GPIO_OSPEED_HIGH | STM32L0_GPIO_OTYPE_PUSHPULL | STM32L0_GPIO_MODE_ALTERNATE));
+
+	    stm32l0_timer_channel(&stm32l0_pwm[instance], g_APinDescription[ulPin].pwm_channel, mapResolution(value, _writeResolution, 12), STM32L0_TIMER_CONTROL_PWM);
 	}
 
-	stm32l0_gpio_pin_configure(g_APinDescription[ulPin].pin, (STM32L0_GPIO_PUPD_NONE | STM32L0_GPIO_OSPEED_HIGH | STM32L0_GPIO_OTYPE_PUSHPULL | STM32L0_GPIO_MODE_ALTERNATE));
-
-	stm32l0_timer_channel(&stm32l0_pwm[instance], g_APinDescription[ulPin].pwm_channel, mapResolution(value, _writeResolution, 12), STM32L0_TIMER_CONTROL_PWM);
-
-	_channels[instance] |= (1u << g_APinDescription[ulPin].pwm_channel);
-
 	return;
     }
 

diff --git a/cores/arduino/wiring_analog.h b/cores/arduino/wiring_analog.h
@@ -60,18 +60,25 @@ extern uint32_t analogRead( uint32_t ulPin ) ;
 
 
 /*
- * \brief Set the resolution of analogRead return values. Default is 10 bits (range from 0 to 1023).
+ * \brief Set the resolution of analogRead return values. Default is 10 bits (range from 1 to 16).
  *
  * \param res
  */
-extern void analogReadResolution(int res);
+extern void analogReadResolution(int resolution);
 
 /*
- * \brief Set the resolution of analogWrite parameters. Default is 8 bits (range from 0 to 255).
+ * \brief Set the sampling period of analogRead in nanoseconds. Default is 2000 nanosceonds (range from 0 to 50000).
  *
  * \param res
  */
-extern void analogWriteResolution(int res);
+extern void analogReadPeriod(int period);
+
+/*
+ * \brief Set the resolution of analogWrite parameters. Default is 8 bits (range from 1 to 16).
+ *
+ * \param res
+ */
+extern void analogWriteResolution(int resolution);
 
 #ifdef __cplusplus
 }