Version 2.1 does not use CH340G — it uses a USBasp bootlaoder, and the microcontorller itself handles USB tasks in software. I’ve attached the script and bootloader file for OS 2.1. You just need to run burn12mhz.sh (make sure you change the programmer to match whatever ISP programmer you are using). The hex file is the bootloader combined with firmware 2.0.7. Once it’s uploaded, you can upload a new firmware through OpenSprinkler’s USB port without using ISP programmer.