After having played around with a MSP430 on a TI launchpad, I got intereste d in onchip debugging. (the TI-launchpad has a spy-by wire interface which works quite nicely)
In the mean time, I have a AVRdragon to play with AVRs using debug-wire and I have also ordered a pickit3. While using the dragon, I got curious about that JTAG-connector on that board, so I started looking at JTAG too. I hav e a STM32 based olimex board I can use for this.
For MSP430 and AVR, it's quite simple to understand.
- your device
- the debugging interface-board (onboard on the TI launchpad board or the S PI or dW interfaces on the dragon)
- a "proxy" application: mspdebug, avarice
- gdb that talks to the proxy application
Sofar, so good. But I have some problems trying to get around how JTAG works.
JTAG is supposed to be a IEEE standard, but
- connectors (10, 14 or 20 pins) do not seams to be standardised
- there are quite a few different interface-boards out there, but quite a f ew of them are marked as "works only with