Cannot set the output pin to 0V

I want to set pin 35 to 0V, to reduce the current at the position I marked in the picture (A to GND)
So that modulate the amplitude of the pwm signal by pin 35.

  • What I expected:
  1. If I set pin 35 as input, the current A to GND increase.
  2. If I set pin 35 as output and set to LOW, pin 35 will go to 0V and the current A to GND will decrease.
  • In real:
    The voltage of pin 35 is ~0.35 V and doesn’t change. (PWM signal voltage is ~1.5v)
    When I just simply connect 35 pin - register - GND and set pin 35 HIGH/LOW, voltage of pin 35 changes.

  • Question:
    Why I cannot pull-down the signal even if I set the pin 35?
    Is pin 35 being pulled-up to the signal pin?)

Is there any solution?

Assume you are talking about the pin 35 of 40-pin header. Please read the 40-pin docs in DLC first. There are some requests to the external device attached to the header.

Thanks for quick reply. I read it but I have too little knowledge about HW stuff to understand it.
I don’t even know what “level shifters”, “driving”, “buffers” mean.
Could you explain with a picture please? (ex> how should I fix the circuit)

After reading the document many times, I think I kind of understand.
So the GPIO pin are connected to the level shifters and if I set the GPIOs as outputs,
they are pulled up/down with the 4 k ohm registors inside the level shifters.
In my case, even if I set the pin 35 to LOW, there is a 4k ohm inside the pin so I cannot directly pull down the signal.

One more question! Do all the Jetson developer kits(not only Nano, Xavier NX, etc) have these level shifters inside the GPIO pin header?

Most Jetson have that. You can check the carrier board schematic first.

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