I have been looking into this (JTAG flash access) as there are many people with a broken ("bricked") unit at the moment. Here's what I have so far:
-All the buzz is about getting a JTAG cable, however the cable is easy to make. Dygnsys (they build the MMSP2 dev boards used by GPH) use a macraigor compatible cable (info from their website). Schematics for those are available on the web. The JTAG pinout (on the GP2X ext connector) is available from the wiki. (If it is correct.)
-So we need software. This is far more difficult as the JTAG standard only specifies the connection and a few commands, the other commands are chip specific. Unfortunately the specs are not publicly available. I do not know if the
Samsung NAND flash chip has a direct JTAG interface or if the JTAG interface is only connected to the MMSP2 which is then used to access the NAND. On the Dignsys I read that they ship their JTAG probe with GDB. (A GPLed software debugger which
can be used to communicate with some devices via JTAG.) GDB does not support flash chips, but Dignsys said the following to me in an e-mail: "The JTAGProbe is our product that sales with Wiggller Compatible hardware equipment with simple
flash upgrade tool.". I can't really draw a conclusion based on that info about which method to access the NAND is used.
-Dignsys sells their JTAG probe with software for $50,-. However the shipping from Korea is very expensive.
-I've asked GBAX when they will have a JTAG cable (and software) and whether it will be for sale, however they have not yet responded.
-On the GP2X forum I just read the following: "I just wanted to let everyone know that I have spoken with Dynamism and they are getting specifics on stocking JTAG cables. If you are looking for one, Dynamism should have them soon.".
So, I've been thinking about buying a cable from Dignsys. I will definitely do so if I break my GP2x. However I find it rather expensive to do so just to attempt to help the community. (The goal of buying one is just to check out their software part so people can (possibly) build their own cable and reflash their unit.) Also I don't want to check things with my working unit. I have not yet contacted GPH about this.
What do you think? Any new info would be very helpful.
Thanks,
Teun
-All the buzz is about getting a JTAG cable, however the cable is easy to make. Dygnsys (they build the MMSP2 dev boards used by GPH) use a macraigor compatible cable (info from their website). Schematics for those are available on the web. The JTAG pinout (on the GP2X ext connector) is available from the wiki. (If it is correct.)
-So we need software. This is far more difficult as the JTAG standard only specifies the connection and a few commands, the other commands are chip specific. Unfortunately the specs are not publicly available. I do not know if the
Samsung NAND flash chip has a direct JTAG interface or if the JTAG interface is only connected to the MMSP2 which is then used to access the NAND. On the Dignsys I read that they ship their JTAG probe with GDB. (A GPLed software debugger which
can be used to communicate with some devices via JTAG.) GDB does not support flash chips, but Dignsys said the following to me in an e-mail: "The JTAGProbe is our product that sales with Wiggller Compatible hardware equipment with simple
flash upgrade tool.". I can't really draw a conclusion based on that info about which method to access the NAND is used.
-Dignsys sells their JTAG probe with software for $50,-. However the shipping from Korea is very expensive.
-I've asked GBAX when they will have a JTAG cable (and software) and whether it will be for sale, however they have not yet responded.
-On the GP2X forum I just read the following: "I just wanted to let everyone know that I have spoken with Dynamism and they are getting specifics on stocking JTAG cables. If you are looking for one, Dynamism should have them soon.".
So, I've been thinking about buying a cable from Dignsys. I will definitely do so if I break my GP2x. However I find it rather expensive to do so just to attempt to help the community. (The goal of buying one is just to check out their software part so people can (possibly) build their own cable and reflash their unit.) Also I don't want to check things with my working unit. I have not yet contacted GPH about this.
What do you think? Any new info would be very helpful.
Thanks,
Teun