The CH340G is a USB to UART Interface chip. It is often used as a cheap alternative to more established brands. I have some CH340G chips, and with only a few extra components one can build a perfectly serviceable USB to TTL-level serial on a breadboard. I test it out by using it to program an ATmega328 on a breadboard over the serial link.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
