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32MB Fuze V1, Checksum error
sss:
That's what I figured.
I might try swapping the #2 and #5 wires around (relative to the fuze), those are nTRST and TCK. The reason being that the clip+ has a similar eight pin jtag connection with those two pins in opposite positions. I read somewhere that nTRST isn't even important with arm and that it could simply be left disconnected.
In the meantime I am waiting for another fuze (it's in the mail) I ordered that's almost totally scrap. I plan on (gently) pulling off the ram module under hot air, cleaning the module and the pads completely (so they are nice and even), and then swapping between one of my good 32MB chips and the old 8MB ESMT chip WITHOUT soldering them to the board. Light pressure should be enough to keep sufficient electrical contact.
Some of the rest of my fuzes, although sold as "junk", I have managed to repair and they are working fine so I don't want to toy with those yet. My original fuze is still attached to a jtag cable and I don't want to disturb it much, small wires tend to break off if agitated enough.
ranma:
--- Quote from: sss on September 16, 2010, 04:47:16 PM ---That's what I figured.
I might try swapping the #2 and #5 wires around (relative to the fuze), those are nTRST and TCK. The reason being that the clip+ has a similar eight pin jtag connection with those two pins in opposite positions. I read somewhere that nTRST isn't even important with arm and that it could simply be left disconnected.
--- End quote ---
Well, it's important enough. :)
It should be at least pulled up, since the device has an internal weak pulldown and a low-level on nTRST means 'reset the JTAG state-machine', so you won't get anywhere while it's low...
--- Quote from: sss on September 16, 2010, 04:47:16 PM ---In the meantime I am waiting for another fuze (it's in the mail) I ordered that's almost totally scrap. I plan on (gently) pulling off the ram module under hot air, cleaning the module and the pads completely (so they are nice and even), and then swapping between one of my good 32MB chips and the old 8MB ESMT chip WITHOUT soldering them to the board. Light pressure should be enough to keep sufficient electrical contact.
--- End quote ---
That would be a neat feat to pull off. :)
I think you can also buy TSOP sockets, but those ain't cheap.
You can figure out the JTAG pinout manually, you just need a debounced switch for manual clocking and some inverters and leds to monitor the pad logic level.
You already know Gnd and Vcc.
Then choose one pin as TRST, one as TCK.
Use the remaining pins as TMS (use a resistor to drive them so you can still see if the device tries to use one of them as TDO and drive out the result).
Set TRST high. Set TMS high and clock a few times (IIRC 5?) until you are sure to have reached the test logic reset state.
Clock in TMS 0 1 0 0 (and leave at 0).
Then you should be in the 'shift DR' state.
Send clocks until one of the 'TMS' pins starts toggling (TDO).
If no pin starts toggling you have chosen the wrong pins for TRST and TCK, repeat with a different pin combination.
If you succeeded you know now TRST, TCK and TDO, finding out TMS and TDI should be pretty easy now.
That's how I figured out the pinout on my C200v2.
Your player may also have SRST pad on the JTAG connector, you can find that one using one of the working fuzes.
If pulling one of the pins low using a 10K resistor resets the device then that's SRST.
sss:
Before I do anything else, I'm going to try pulling up nTRST with a 10 or 15kohm resistor and giving jtag another go the way it is. I read about another rockbox user needing to do this with his sansa (forget which model), but at the time I thought he did it to address a flaw in the design of the wiggler he assembled to connect with. Now that I am hearing this again I think it's worth a shot. By the way, the scrap fuze I ordered came, but it's a V2 and it doesn't have any external ram >:(. Nice to have a spare V2 for testing but not what I was looking for at the moment. I am going to stick with only 2GB fuzes in the future since most of those seem to be V1s. I might still try the memory swap test I was planning on doing but I'll have to do it on one of my fully functional V1 fuzes.
sss:
SUCCESS ;D Got back to this project after finishing several other affairs and getting a new bus pirate to JTAG with.
Posted my JTAG findings in the Wiki here: http://www.rockbox.org/wiki/SansaAMSJTAG
I was having poor luck with my cheap parallel interface so I upgraded to something more useful and I do not regret it!
Now that I have JTAG working, I'm wondering what commands I need to enter to get the registers set correctly so that the extra ram can be properly used (?)
sss:
I also succeeded in upgrading the player memory ;D
I will post photos when I get a chance.
Most of the posters were right (so was my initial intuition). So long as the ram is compatible, there is no need to mess with any settings (at least to get the player running). Recognizing the additional ram of course does require special firmware settings.
Here's what happened:
*Got sick of waiting for a few extra semi-broken players to test (USPS lost my damn package), modded another working V1 fuze and somehow it became completely non-working despite doing a perfect soldering job. Heat must have killed some unusually sensitive component, not worth my time figuring out which one (CPU?)
*Went back to the fuze I had connected to JTAG wires. Took those off since they were in the way (lot of work for nothing but now we have the Fuze JTAG pinout). Fluxed the ram chip again, went over my joints another time and NOW the thing boots! :o Apparently there was in fact a bad joint somewhere I had long overlooked. I couldn't believe it.
Well it was fun, I have a bunch of extra chips so I will get to work on whipping up a few 32MB fuzes out of what I have left and what I can find.
I have a few friends who wanted one, so after I'm done with those, I will put together a handful for rockbox users who've always wanted a 32MB fuze!
Sorry this project took so long! I had a few other priorities and I really stuck this on the back burner for quite a while! Had I known for a fact it was just a bad joint all along, I would have gotten on this a lot sooner.
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