cpu/stm32_common: consider timer multiplier for PWM

cpu/stm32_common/cpu_common.c

@@ -24,6 +24,28 @@
 #define ENABLE_DEBUG (0)
 #include "debug.h"
 
+/**
+ * @brief   Timer specific additional bus clock prescaler
+ *
+ * This prescale factor is dependent on the actual APBx bus clock divider, if
+ * the APBx presacler is != 1, it is set to 2, if the APBx prescaler is == 1, it
+ * is set to 1.
+ *
+ * See reference manuals section 'reset and clock control'.
+ */
+static const uint8_t apbmul[] = {
+#if (CLOCK_APB1 < CLOCK_CORECLOCK)
+    [APB1] = 2,
+#else
+    [APB1] = 1,
+#endif
+#if (CLOCK_APB2 < CLOCK_CORECLOCK)
+    [APB2] = 2
+#else
+    [APB2] = 1
+#endif
+};
+
 uint32_t periph_apb_clk(uint8_t bus)
 {
     if (bus == APB1) {
@@ -34,6 +56,11 @@ uint32_t periph_apb_clk(uint8_t bus)
     }
 }
 
+uint32_t periph_timer_clk(uint8_t bus)
+{
+    return periph_apb_clk(bus) * apbmul[bus];
+}
+
 void periph_clk_en(bus_t bus, uint32_t mask)
 {
     switch (bus) {

cpu/stm32_common/include/periph_cpu_common.h

@@ -297,6 +297,15 @@ typedef struct {
  */
 uint32_t periph_apb_clk(uint8_t bus);
 
+/**
+ * @brief   Get the actual timer clock frequency
+ *
+ * @param[in] bus       corresponding APBx bus
+ *
+ * @return              timer clock frequency in Hz
+ */
+uint32_t periph_timer_clk(uint8_t bus);
+
 /**
  * @brief   Enable the given peripheral clock
  *

cpu/stm32_common/periph/pwm.c

@@ -42,10 +42,10 @@ static inline TIM_TypeDef *dev(pwm_t pwm)
 
 uint32_t pwm_init(pwm_t pwm, pwm_mode_t mode, uint32_t freq, uint16_t res)
 {
-    uint32_t bus_clk = periph_apb_clk(pwm_config[pwm].bus);
+    uint32_t timer_clk = periph_timer_clk(pwm_config[pwm].bus);
 
     /* verify parameters */
-    assert((pwm < PWM_NUMOF) && ((freq * res) < bus_clk));
+    assert((pwm < PWM_NUMOF) && ((freq * res) < timer_clk));
 
     /* power on the used timer */
     periph_clk_en(pwm_config[pwm].bus, pwm_config[pwm].rcc_mask);
@@ -66,7 +66,7 @@ uint32_t pwm_init(pwm_t pwm, pwm_mode_t mode, uint32_t freq, uint16_t res)
 
     /* configure the PWM frequency and resolution by setting the auto-reload
      * and prescaler registers */
-    dev(pwm)->PSC = (bus_clk / (res * freq)) - 1;
+    dev(pwm)->PSC = (timer_clk / (res * freq)) - 1;
     dev(pwm)->ARR = res - 1;
 
     /* set PWM mode */
@@ -95,7 +95,7 @@ uint32_t pwm_init(pwm_t pwm, pwm_mode_t mode, uint32_t freq, uint16_t res)
     dev(pwm)->CR1 |= TIM_CR1_CEN;
 
     /* return the actual used PWM frequency */
-    return (bus_clk / (res * (dev(pwm)->PSC + 1)));
+    return (timer_clk / (res * (dev(pwm)->PSC + 1)));
 }
 
 uint8_t pwm_channels(pwm_t pwm)

cpu/stm32_common/periph/timer.c

@@ -23,28 +23,6 @@
 #include "cpu.h"
 #include "periph/timer.h"
 
-/**
- * @brief   Timer specific additional bus clock presacler
- *
- * This prescale factor is dependent on the actual APBx bus clock divider, if
- * the APBx presacler is != 1, it is set to 2, if the APBx prescaler is == 1, it
- * is set to 1.
- *
- * See reference manuals section 'reset and clock control'.
- */
-static const uint8_t apbmul[] = {
-#if (CLOCK_APB1 < CLOCK_CORECLOCK)
-    [APB1] = 2,
-#else
-    [APB1] = 1,
-#endif
-#if (CLOCK_APB2 < CLOCK_CORECLOCK)
-    [APB2] = 2
-#else
-    [APB2] = 1
-#endif
-};
-
 /**
  * @brief   Interrupt context for each configured timer
  */
@@ -78,8 +56,7 @@ int timer_init(tim_t tim, unsigned long freq, timer_cb_t cb, void *arg)
     dev(tim)->ARR  = timer_config[tim].max;
 
     /* set prescaler */
-    dev(tim)->PSC = (((periph_apb_clk(timer_config[tim].bus) *
+    dev(tim)->PSC = ((periph_timer_clk(timer_config[tim].bus) / freq) - 1);
-                       apbmul[timer_config[tim].bus]) / freq) - 1);
     /* generate an update event to apply our configuration */
     dev(tim)->EGR = TIM_EGR_UG;