📘 Introduction

Over the past four years, I’ve been exploring ways to simplify and automate the process of programming microcontrollers using FTDI and UPDI. What began as a quick solution to flash an ATtiny gradually turned into a deep dive into one-wire programming, signal integrity, level shifting, and programmer design.

This documentation captures the entire journey — from early prototypes and failed attempts to stable builds and design insights. It includes various hardware setups, testing results, firmware tweaks, and practical tips learned along the way.

Whether you're building your own UPDI programmer or just curious about the process, this is a reflection of what worked, what didn’t, and everything in between.

The 4 year Collection of Test and trials:)

Switchable FTDI UPDI Converter using SPDT switch - 2021

Image Credits:- https://academy.cba.mit.edu/classes/embedded_programming/index.html

Documentation Link :- https://fabacademy.org/2021/labs/kochi/students/saheem-palayi/assignments/week10.html#UPDI-programer

Issues

• I couldn't made it work with just one SPDT switch which was switching the FTDI RX pin between UPDI pin and Target TXD pin. cant upload after uploading serial print programs
• Since it wont work when we upload a serial print program then added additional switch for switching FTDI’s RX, target’s TX line as well ,
• UPDI on the end pin config instead of DTR/RTS forcing to design the MCU circuit’s with a 6 pin FTDI converter always

Switchable FTDI UPDI Converter Using DPDT Switch made - 2024