If anyone is looking for a cheap USB to serial adapter that will work down to 1.8V, the standard cheap models like
these should work fine with the VCC_325 pin on 1.8V instead of 3.3V, the guy on the link set his to 5V for his purposes.
I have a few of these lying around some of which I got for <£3 on ebay.
I just need to put something together for the kindle adapter now
.
G