Loads hex file on command line
Based on https://github.com/dcwbrown/dwire-debug/tree/master
other dWire code https://github.com/dwtk/dwtk/blob/master/debugwire/flash.go
Best used with FTDI or CP2104 USB serial adapter with 1K ohm resistor from TxD to RxD then on to dWire pin