Merge pull request #1706 from LMESTM/fix_pwmout

Fix pwmout for STM32F3

Author: 0xc0170

libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3/TARGET_DISCO_F303VC/objects.h

@@ -99,6 +99,7 @@ struct i2c_s {
 struct pwmout_s {
     PWMName pwm;
     PinName pin;
+    uint32_t prescaler;
     uint32_t period;
     uint32_t pulse;
     uint32_t channel;

libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3/TARGET_DISCO_F334C8/objects.h

@@ -99,6 +99,7 @@ struct i2c_s {
 struct pwmout_s {
     PWMName pwm;
     PinName pin;
+    uint32_t prescaler;
     uint32_t period;
     uint32_t pulse;
     uint32_t channel;

libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3/TARGET_NUCLEO_F302R8/objects.h

@@ -99,6 +99,7 @@ struct i2c_s {
 struct pwmout_s {
     PWMName pwm;
     PinName pin;
+    uint32_t prescaler;
     uint32_t period;
     uint32_t pulse;
     uint32_t channel;

libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3/TARGET_NUCLEO_F303K8/objects.h

@@ -99,6 +99,7 @@ struct i2c_s {
 struct pwmout_s {
     PWMName pwm;
     PinName pin;
+    uint32_t prescaler;
     uint32_t period;
     uint32_t pulse;
     uint32_t channel;

libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3/TARGET_NUCLEO_F303RE/objects.h

@@ -99,6 +99,7 @@ struct i2c_s {
 struct pwmout_s {
     PWMName pwm;
     PinName pin;
+    uint32_t prescaler;
     uint32_t period;
     uint32_t pulse;
     uint32_t channel;

libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3/TARGET_NUCLEO_F334R8/objects.h

@@ -99,6 +99,7 @@ struct i2c_s {
 struct pwmout_s {
     PWMName pwm;
     PinName pin;
+    uint32_t prescaler;
     uint32_t period;
     uint32_t pulse;
     uint32_t channel;

libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3/pwmout_api.c

@@ -96,7 +96,7 @@ void pwmout_write(pwmout_t* obj, float value)
 
     // Configure channels
     sConfig.OCMode       = TIM_OCMODE_PWM1;
-    sConfig.Pulse        = obj->pulse;
+    sConfig.Pulse        = obj->pulse / obj->prescaler;
     sConfig.OCPolarity   = TIM_OCPOLARITY_HIGH;
     sConfig.OCNPolarity  = TIM_OCNPOLARITY_HIGH;
     sConfig.OCFastMode   = TIM_OCFAST_DISABLE;
@@ -161,8 +161,26 @@ void pwmout_period_us(pwmout_t* obj, int us)
     // Update the SystemCoreClock variable
     SystemCoreClockUpdate();
 
-    TimHandle.Init.Period        = us - 1;
-    TimHandle.Init.Prescaler     = (uint16_t)(SystemCoreClock / 1000000) - 1; // 1 us tick
+    /* To make it simple, we use to possible prescaler values which lead to:
+     * pwm unit = 1us, period/pulse can be from 1us to 65535us
+     * or
+     * pwm unit = 500us, period/pulse can be from 500us to ~32.76sec
+     * Be careful that all the channels of a PWM shares the same prescaler
+     */
+    if (us >  0xFFFF) {
+        obj->prescaler = 500;
+    } else {
+        obj->prescaler = 1;
+    }
+    TimHandle.Init.Prescaler     = ((SystemCoreClock / 1000000) * obj->prescaler) - 1;
+
+    if (TimHandle.Init.Prescaler > 0xFFFF)
+        error("PWM: out of range prescaler");
+
+    TimHandle.Init.Period        = (us - 1) / obj->prescaler;
+    if (TimHandle.Init.Period > 0xFFFF)
+        error("PWM: out of range period");
+
     TimHandle.Init.ClockDivision = 0;
     TimHandle.Init.CounterMode   = TIM_COUNTERMODE_UP;
 

libraries/tests/mbed/pwm/main.cpp

@@ -19,15 +19,15 @@ float value = 0.75;
 int main() {
 #if defined(TARGET_FF_ARDUINO)
     PwmOut pwm(D9);
+    int period_ms = 10;
 
-    pwm.period_ms(10);
+    pwm.period_ms(period_ms);
     pwm.write(value);
 
     float result = floor(pwm.read() * 100 + 0.5) / 100; // round it to 0.xx
-    printf("Initialize PWM on pin D9 with duty cycle: %.2f\n", result);
+    printf("PWM period = %dms with duty cycle: %d%%\n", period_ms, (int) (result * 100));
 
     notify_completion(result == value ? true : false);
-
 #elif defined(TARGET_LPC1768) || defined(TARGET_LPC2368) || defined(TARGET_LPC11U24) || defined(TARGET_LPC4088) || defined(TARGET_LPC2460)
     PwmOut pwm_p25(p25);
     PwmOut pwm_p26(p26);