http://hackaday.com/2014/01/23/arm-debugger-for-nearly-one-dollar/
Oh that title is so misleading.
But if you squint your eyes and scratch your noggin it’s almost true.
Thanks to the hard work of [Peter Lawrence] it is now possible to hack together
an extremely inexpensive CMSIS-DAP ARM debugger.
Let’s talk about function and we’ll get back to cost later.
CMSIS-DAP is a standard that gives you the kind of breakpoint control you expect from a proper debugger.
In this case [Peter] implemented the standard using 4k words of space on a PIC 16F1454.
This lets it talk to the debug port on ARM chips, and the bootloader (also written by him)
doubles as a USB-to-UART bridge. Boom, done.
OpenOCD (and a couple of other software packages) talks to the PIC and it talks to the ARM. Nice.
Back to the cost question.
You can get a 16F1454 for nearly a dollar when you order in quantity.
If you cut up an old USB cable, recycle some jumper wire, and already have power
and decoupling on hand, you’re in business for nearly one dollar.