On Tue, Jul 26, 2011 at 9:46 PM, erik quanstrom <quans...@quanstro.net> wrote: > can someone point me at a list of plan9 usb/serial compatable > jtag programmers? >
As far as I know, ft2232 chips and their variants may work, but I have only tried it with the Sheeva plug. The ft2232 serial chip inside the sheeva can drive all sorts of serial things, including input to a jtag state machine if connected properly. Inside the sheeva plug (and some other arm boards), the chip is actually connected to the jtag input of the SOC inside it, but you need the concret details on how this is done for what you are using. What I do is I program (this is what usb/serial does) the interface connected to the jtag for the right configuration to drive it. The device is also programmable and you need to program it (it is done so that the latency of the USB does not kill you). Then you need to communicate with the other side, which includes driving the reset bits (which depend on the concrete electronics connecting the serial chip to the jtag interface) and then sending the right commands. I did that for the Arm inside the sheeva, exposing it as a /proc interface and an acid library on top of it. Inside my contrib directory there is a file jtag.tgz with all the stuff I have been playing with. All the layers serial chip/mpsse assembler/jtag state machine driver/arm chain driver/proc filesystem have been carefully separated, so you can replace any of the interfaces should you have a different hardware, though all this is an ongoing job and may change, so if you do work on it, talk to me off-list. Enjoy. G.
