PMOD-USB-UART

A tiny PMOD module that turns USB into UART. Built around a CH340C, it plugs into any PMOD UART socket and adds a serial console over a standard USB-B cable.

What's on the module

• A CH340C USB-UART converter.
• A USB-B connector.
• A PMOD UART header with TX, RX, CTS and RTS.
• Two blue LEDs.
• A 5V/3.3V select jumper.

The data path

USB comes in on the B connector and the CH340C bridges it to UART. TXD and RXD pass through 100R series resistors to the PMOD header, with CTS and RTS brought out for flow control. Two blue LEDs blink on the TX/RX lines. I used the CH340C because it needs no crystal.