3 Pin UART Header 2J1 on Le Potato


I’m trying to understand why this UART only has 3 pins while I was checking all those serial adapters selling on taobao with 4 pins? This can be super noob, but where is the vcc, why we don’t need it here but the GND?Is the GND there purely for overload prevention?

BTW, I hope the header is not just reserved for debugging, because I’m thinking of using the separate one as a generic uart port.

USB to UART adapters often include Vcc pins for powering UART devices that are not self-powered (think things like GPS modules). For a device like the Le Potato, which is considered to be self powered (via the MiniUSB connector), a UART adapter would not be needed to provide power.

The way UART works is that signals are sent at voltages relative to ground at a specified speed (the baud rate). Tx, Rx, and GND are required for bi-directional UART communication , and the GND pin is very important so that both the Le Potato and the USB UART adapter operate same ground reference. In this case, the Vcc pin on USB UART adapters can be left disconnected and ignored completely.

A word of warning, though: do not attempt to power the Le Potato using the Vcc pin on your USB UART adapter. Most of them are only capable of providing 50-100mA, and the Le Potato needs at least 500-1000mA to operate correctly. The Le Potato probably won’t be damaged if you do this, but the USB UART will almost certainly be burned up. This is easily avoided by simply never connecting the Vcc pin.


The UART adapter will simply fail to deliver enough power to the board and the board will experience non-fatal brown-out. There should be no damage to either device unless something was hooked up improperly like 5V power pin to a 3.3V GPIO pin or ground.

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Feedback: Eventually I switched back to uarta instead of uart-ao-b for my home lab experiments, as I’m not sure the corresponding interface. For uarta I learned another day it is /dev/ttyAML6, but I don’t know where to look at for uart-ao-b.

We made a guide here: Libre Computer Board Serial UART Connection and Setup Guide

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