UART test headers on PCBs provide access to serial debug consoles on embedded systems. The standard 4-pin 2.54mm header carries VCC, GND, TX, and RX for connecting USB-UART adapters during development.
| Pin | Name | Function | Type |
|---|---|---|---|
| 1 | VCC | Target supply voltage | PWR |
| 2 | GND | Ground | GND |
| 3 | TXD | Transmit data from target | BUS |
| 4 | RXD | Receive data to target | BUS |