JTAG provides a low-level hardware debugging interface to a variety of processors, including the PXA255 on the gumstix. FAQ information on gumstix Development and Programming here.
Run this macro script in OCD Commander and it should initialize the gumstix, load u-boot to RAM, and execute it.
Well, not so much an entire schematic as the connections. This does it for our internal JTAG board.
JTAG Signal locations (Basic and Connex)
Commercial JTAG adaptors
- IAR jlink - USB 2.0 - $199.00 (Currently Win32 support only)
- jlink - This unit is the same as the IAR version. This software is to be used with the IAR unit.
- Macraiger Wiggler - Parallel Port - $150
- ARM JTAG - A JTAG wiggler clone from SparkFun.
- Abatron BDI - Ethernet host interface JTAG emulators
More listed at the JTAG debugger FAQ.
Build your own JTAG adaptor
This page shows a schematic for making your own parallel port JTAG adapter.
This page provides details on using OpenOCD to reflash a gumstix: HOWTO: Reflash using JTAG and OpenOCD
Using the Tweener to make a JTAG
NOTICE: This Tweener/JTAG information only applies if your motherboard is revision G or older. The JTAG signals are not brought through the 60 pin Hirose connector on newer boards.
This will evolve into instructions for creating a JTAG using a tweener board. The photo below identifies where the JTAG connections from above should go.
If you're going to be using the JTAG with a daughtercard which has a console (FFUART) on it (i.e. console or robostix), then you should cut the indicated trace (on the back side of the tweener board) where the right hand red line, which effectively disconnects the serial port on the tweener board. If you'd like to use the console on the tweener board, then cut the trace where the left red line is. If you're using a daughtercard with no console (like the audiostix), then no cuts are required.