GPIO pin on J12 module output 3.3v voltage seems not work

Recently I used GPIO pin on J12 module of Jetson Xavier NX to drive an audible LED by sending 3.3v voltage. I tested the LED with the default 3.3v power supply in J12, it worked well. But when I use GPIO (such as pin 31) as power source and tested with python script to drive it, the light looked dimmer than usual and no alarm sound yet. I detected voltage and current for the GPIO pin and the default 3.3v power supply with multimeter, the value looked totally the same. What could be the reason for the issue? do anybody have ideas?

GPIO is not intended to provide much supply current. An LED would greatly overload the ability to supply current. You should use a buffer and not actually power the LED through GPIO.

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what should i use as a buffer? in my case i am using bjt driven relay .

I do not know how much current the bjt driven relay requires. However, if not much current is required due to built in buffering, then you could drive this directly. If more current is required, but the current is low enough for something like a common TTL buffer or inverter to work with, then you could use that. The main point is that GPIO is a logic output, and not intended for significant supply of current.

Someone else may have advice on specific buffers or drivers used to allow GPIO to output more current.