A couple of years ago I realized I needed a way to debug my apps on GP32, so I slapped together a GDB stub that was using the USB device capabilities of the GP32 to communicate with the PC. On the PC side a small server had to be running, it talked USB with the GP32 and TCP/IP with GDB. It was very cumbersome to use, so i made myself a simple UART cable for the GP32 instead and rewrote parts of the stub to use UART communications instead, it made debugging much easier. Using UART instead of USB made it easy to add CTRL-C functionality from GDB. Anyway, you can find both versions of the stub in the Download section. The gdbserver here is only for linux(Mac OSX aswell?), it should probably work on most systems supported by libusb. One has to build the program with the stub in order to use it, also one must make a couple of calls from main() or something to hook exception vectors etc. Also, mr_spiv's MultiFW or the modified FW from the Download section is required. It's possible to make the stub work without a modified FW aswell, but since I already have a modified FW i don't really care. And yes, there exists a version of the stub that is ready for integration with the FW so one wouldn't need to build it with each application however, it has not been released.