HardwareTimer: Keep alternate function for F1 family

For the F1 family the GPIO pin associated with a capturing timer not only
has to be forced to input mode, but its alternate function still has to
be set according to PinMap_PWM.

Author: treitmayr

cores/arduino/HardwareTimer.cpp

@@ -672,7 +672,12 @@ void HardwareTimer::setMode(uint32_t channel, TimerModes_t mode, PinName pin)
       if ((mode == TIMER_INPUT_CAPTURE_RISING) || (mode == TIMER_INPUT_CAPTURE_FALLING) \
           || (mode == TIMER_INPUT_CAPTURE_BOTHEDGE) || (mode == TIMER_INPUT_FREQ_DUTY_MEASUREMENT)) {
         // on F1 family, input alternate function must configure GPIO in input mode
-        pinMode(pin, INPUT);
+        uint32_t function = pinmap_find_function(pin, PinMap_PWM);
+        if (function != (uint32_t)NC) {
+          // force input mode
+          function = (function & ~STM_PIN_FUNCTION_BITS) | (STM_MODE_INPUT << STM_PIN_FUNCTION_SHIFT);
+          pin_function(pin, function);
+        }
       } else
 #endif
       {

libraries/SrcWrapper/src/stm32/pinmap.c

@@ -121,6 +121,10 @@ void pin_function(PinName pin, int function)
   switch (mode) {
     case STM_PIN_INPUT:
       ll_mode = LL_GPIO_MODE_INPUT;
+#if defined(STM32F1xx)
+      // on F1 family, input mode may be associated with an alternate function
+      pin_SetAFPin(gpio, pin, afnum);
+#endif
       break;
     case STM_PIN_OUTPUT:
       ll_mode = LL_GPIO_MODE_OUTPUT;