StackRduino
diff --git a/‎ports/stm32f4/common-hal/pulseio/PWMOut.c‎
Lines changed: 3 additions & 2 deletions b/‎ports/stm32f4/common-hal/pulseio/PWMOut.c‎
Lines changed: 3 additions & 2 deletions
@@ -68,8 +68,9 @@ STATIC uint32_t timer_get_source_freq(uint32_t tim_id) {
 }
 
 STATIC uint32_t timer_get_internal_duty(uint16_t duty, uint32_t period) {
-    //duty cycle is duty/0xFFFF fraction x (number of pulses per period)
-    return (duty*period) / ((1 << 16) - 1);
+    //duty cycle is (0xFFFF - duty)/0xFFFF fraction x (number of pulses per period)
+    //Note that pulses are inverted, so duty cycle is inverted
+    return ((0xFFFF - duty)*period) / ((1 << 16) - 1);
 }
 
 STATIC void timer_get_optimal_divisors(uint32_t*period, uint32_t*prescaler,
Original file line number	Diff line number	Diff line change
`@@ -68,8 +68,9 @@ STATIC uint32_t timer_get_source_freq(uint32_t tim_id) {`
`68`	`68`	`}`
`69`	`69`
`70`	`70`	`STATIC uint32_t timer_get_internal_duty(uint16_t duty, uint32_t period) {`
`71`		`- //duty cycle is duty/0xFFFF fraction x (number of pulses per period)`
`72`		`- return (duty*period) / ((1 << 16) - 1);`
	`71`	`+ //duty cycle is (0xFFFF - duty)/0xFFFF fraction x (number of pulses per period)`
	`72`	`+ //Note that pulses are inverted, so duty cycle is inverted`
	`73`	`+ return ((0xFFFF - duty)*period) / ((1 << 16) - 1);`
`73`	`74`	`}`
`74`	`75`
`75`	`76`	`STATIC void timer_get_optimal_divisors(uint32_tperiod, uint32_tprescaler,`