Hi Jon
thanks very much for everything you've posted, you have no idea how much trouble you have saved me!
I have my qt300 sending SPI to my arduino, but now I want to use the 1-wire UART mode of the qt300, since it will greatly reduce the wiring complexity of my system ( I am using multiple qt300s). I already have code to do the 1-wire comm, but I first need to change modes of the qt300.
According to this thread on the quantum forum:
http://www.qprox.com/forum/read.php?1,1370
You can program the chips to change modes with only a microcontroller, rather than buying the programmer.
I am about to do this, but I wanted to check if anyone here has done this, and can give some pointers.