Reading the PWM output state on STM32F4

Question

I would like to determine in software if the PWM output signal is currently high or low.

As far as I know GPIO_ReadOutputDataBit(GPIOD, GPIO_Pin_12) does not work with a GPIO pin set up as an alternate function (AF).

• Lundin: Some microcontrollers have a "port state" register that can give the actual voltage level (active/inactive) of a port, regardless of if it is configured as output or input. If such registers can be used when a peripheral hardware is using the same port also depends on the specific MCU. So I would suggest to read the chapter describing the gpio hardware in the manual.

Answer 1

You should read the applicable GPIO input data register, not the output one. Only when the pin is configured as a GPIO output would they match.

The programmer's manual will explain what the actual register is; the documentation for whatever IO or HAL library you are using will show how to read it at a higher level.

It is also likely that you should be able to read the relevant timer's count register and compare it to the applicable output compare value.

Answer 2

I can't find a place in the timer register structure to directly read OCxREF or OCx, but you may have luck with this:

Set an interrupt on the update and reset timer events and set a flag manually that way.

Although the output state may be reflected in the GPIO input state as Chris Stratton mentions as well.