Re: [9fans] JTAG

[EBo <ebo@sandien.com>]

 I've used JTAG to debug and program a couple of embedded systems.  I
 even had an automated regression test suite that tested some AVR
 hardware using gdb running on Gentoo talking to an JTAG.  Freaky but
 fun.

 If I recall correctly many chips will allow you to see and twiddle
 internal registers and states of sub-blocks in the integrated circuits.
 I never had the call to go to that level, but some have.  What little I
 remember is that the JTAG standard dictates the timing and pin-out on a
 20 pin connector.  But I also remember that the ARM and AVR JTAG units I
 saw do not play together, but there might be some universal JTAG
 interfaces now.

 Several years ago I was told to stay clear of the USB interfaced JATGs
 and to use a USB/RS232 converter hooked up to a RS232/JTAG interface as
 this was more reliable.  That was years ago, and things are likely more
 stable now.  I also remember seeing some open source hardware/software
 JTAG efforts.  That might make a good place to start working through the
 JTAG protocal.

 Hope that helps.

   EBo --

 On Tue, 26 Oct 2010 19:49:46 +0100, Steve Simon wrote:
> I am intrigued, what facalities would jtag software provide on plan9,
> is the idea a virtual filesystem which would communicate with a
> fairly
> dumb jtag interface connected to (say) a PC's printer parallel port,
> or may there is some standardised USB interface?
>
> I jse jtag probes from time to time but I have never thought about
> the code to
> implement what is on the probe...
>
> What was discussed (roughly).
>
> -Steve