One of my Seagate dockstars has died and is giving no signs of life to the serial console.
I've checked:

• all the fuses I could see,
• all the ref tensions I could find,
• the SOC xtal

and all seem fine so my next suspect is the flash. I don't want to desolder it and I don't have a programmer for it anyway so I was thinking that maybe I could have a peep via jtag if the sock is trying to read from flash without success.

I don't have a jtag debugger (and I've never used one either) so I was wondering if I could use an rPI as a jtag debugger ?
I know you can run openocd on the PI but can I use the PI's GIPO ports to directly interface with the dockstar's jtag port.

I've done a little searching and found Using a Raspberry Pi as a JTAG Dongle where some dude uses the PI to do more or less what I want to do but on the other end the micro-controller is DUINO.

How much of that is usefull as a starting point for what I want to do ?
How much more on top of that needs to be done to reach my goal ?

Unless you know what you're doing, I advise leaving the hardware. It's easier to damage than repair it. You know about jtag, s I take it you have some knowledge.

I was in the electronic hardware repair business until I was effectively driven out of it by a combination of factors. JTAG is a manufacturing test that verifies connections to devices, and is little use in repair. It's Go/NoGo & not diagnostic. The most effective repair techniques without manufacturer support were Analogue Signature Analysis, and In Circuit Test, which has limited availability.

Usually, it boils down to this: What can I replace? Is that blown? You probably won't be able to get much, because nobody fixes stuff anymore, so stocking parts is rarely profitable.

Manufacturers sometimes have a repair option where repairs are processed through the production line test facilities. Use that if it's available. Otherwise. cry.

If the flash is broken I know it cannot be mended via jtag ... but if it was just wiped I can mend that with jtag.
In any case I'd like to see if the ARM core is still detected from jtag just to make sure that at least the SOC is OK.


I'm not going to cry over it ... I've plenty of other ARM boards to play with.
It would still be interesting to setup a PI to access other ARM hardware via jtag.