What is it?

This cable allows programming my UPDI development boards, and possibly others, without having a mounted header socket. The programming connector uses spring pins that just need to touch the UPDI pad. The cable length is a minimum of 12" (30.5cm) in length. Note that the actual heat shrink tubing color may vary from those in the images.

Why did you make it?

This cable was made to support my development boards used for adding electronics to scale model builds or other areas where compact SOC is needed. By eliminating the programming socket it keeps the board as small as possible for placement in confined areas. This cable also has the schottky diode and 470 ohm resistor built into the cable for converting tx/rx signals to UPDI. It has a set of flying leads to attach to a USB to Serial Converter such as CH340. I've tested this cable with the CH340E and CH9340C.

What makes it special?

This cable makes it easy to program a UPDI AVR part using a 3-pin UPDI header for the UPDI signal to pin 3 of the AVR device such as an AVR DD series. No socket is need for programming. See my AVR SOIC20 development board for an example.

Additional Information

For more information on SerialUPDI and Arduino Core support

The Arduino IDE has programming support for Serial UPDI.

Cable Flying Lead Connections

• Connect the Red(+) and Black(-) leads to a power source for programming the part. Most USB to Serial converters have a 5v source and some also include a 3.3volt.
• Connect the labeled TX lead to the TX of the converter
• Connect the labeled RX lead to the RX of the converter

Using the CH340E or the CH9340C the baud rates listed below are known to work with the Arduino IDE.

• SerialUPDI - Slow: 57600 baud
• SerialUPDI - 230400 baud
• SerialUPDI - Fast: 4.5v+ 460800 baud (CH340 – and maybe some others)
• SerialUPDI – TURBO: 4.5v+ 912600 baud (CH340 (and maybe some others) only)