Don't throw away those CH340 USB-Serial just yet!

[eventhorizon]

I bought this CH340 based USB to Serial adapter in the past hoping that I would be able to program using my netbook. The thing is, it doesn't work with serial programmers, and it never will. I am using an ATMEGA8, and flashed in a UART Bootloader, then changed the BOOTRST so that it will run the bootloader on power-up. After that, I connected the ATMEGA8's TX/RX pins to the !RX/!TX (*note the "!") pins of the CH340 adapter. I downloaded and ran a GUI version of FBoot, then powered up my mega8 (yes, in that order, or simply reset the mega8 if it's already turned on after running FBoot.) , and it flashed successfully.

The reason for the !RX/!TX is that the CH340 is not RS-232. It is actually a USB-to-TTL, and the outputs (and inputs) are inverted. I simply used a 74LS04 to invert the signals. That's it! I can now use my netbook to do some AVR programming without more expensive programmer (or and arduino in some cases).