What is the minimal required injected current for the one-pulse mode is it the same that for an GPIO input ?

Julien33 · ‎2022-05-23

Hi I'm currently working with a Nucleo board STM32F401RE with the one pulse mode.

The one pulse mode enables me to capture a trigger in input and re-deliver it with a controlled delay.

The tigger comes from an optical endstop sensor mades up with a infrared led and a photo transistor.

This sensor works well when I connect it to a pin with a GPIO input. Yet when I plug it to the input of the one pulse mode, the sensor doesn't work at all. It seems like all the current from the sensor is drained by the MCU. The configuration of the one pulse mode is on TIM4 and is showed below.

Yet when I'm using a interruptor which directly supply the input with 3.3V output from the board it works.

I read the documentation about the injected current required to trigger the input from a one pulse mode but I only saw these values for input/output below:

I also think that the fact to switch in one pulse mode add a resistor connection on the input pin but I found nothing about it...

It would be important because I would like to add a comparator circuit between the one pulse input pin and the endstop sensor.

Sincerely yours,

Julien