GPIO output voltage

[Karl_L]

Hi

I have a esp32 devkit1. I'm using the GPIO 4 (BIT4 in my program) to control something that expects 3.3V. The devkit1 is just powered by USB.

It seems the output is quite low sometimes, like 2.7V.

Are all GPIOs outputting the same voltage?

Is my board defective or is this usual?

Thanks.

[ESP_Sprite]

What are you trying to control? If you measure the 3.3V pin on the devboard, what voltage does it give you?

[Mr_Red]

Are you using your IO to power a module/chip or just as a signal?

If using to power, voltage will drop the more current the IO will source. This is a simplification, but think of the IOs as FETs with an RDS(on). The more current you'll sink/source, the higher the voltage drop in the chip. According to the datasheet (ESP32 Datasheet V2.4 section 5.3 DC Characteristics), you can expect this kind of voltage if sourcing around 40mA from your IO.

High-level source current (VDD = 3.3V, VOH = 2.64V, PAD_DRIVER = 3) Typ. 40mA

[Karl_L]

Thanks. I've unplugged everything and just checked the 3.3V pin, and indeed it was providing 3.3V. Rechecking the voltage at the GPIO, it's properly showing 3.3V now. I'm not sure why it was close to 2.7V previously.

I'm not trying to power a chip, I'm just plugged to the GPIO of another board. One of the problem is that the size of the pins on each board is different, so I had to re purpose an existing cable and the connection may not be perfect.