XMOS Chip Stuck on old Firmware (SMSL M500 USB DAC)

[mon2]

Curious to ask - was your PCB stack really really tight to remove from the back end of the enclosure? Honestly had muscle cramps as the width of the PCBs were so tight to slide out.

[overherz]

i had no problems, i just didn't know how the wires were connected, so they just broke out of the connectors ))

[jdoe]

So far I was able to disassemble and assemble back M500. It was slightly hard to attach display cable back to the digital processing board, but still manageable

how did you do this? I reflashed, but I cannot remove the front panel, because the bolts are under the glass, and I do not know how to remove it

Hi, I didn't remove front panel, because I disconnected cable from board only and left the other side connected to the from panel.

[jdoe]

My parcel with EEPROM programmer tool (which I've ordered few months ago) lost somewhere on the way from China, so I've ordered flash chips separately (https://www.ebay.com/itm/332189425791) just in case if original would be damaged, because I was going to use raspberry pi to re-write eeprom using SPI.
Thanks to overherz we know that CH341A works fine with W25X40 flash series, which is much easier and cheaper to buy from local dialer (it costs 7$ at local online electronics shop).
Just in case if someone needs flex cable, here is ebay item: https://www.ebay.com/itm/263406086176 (I've ordered both forward and reverse 24 pin versions for 0.5mm pitch and 40cm long, cause I was unable to check which side pins on the front panel connector).

[jdoe]

Curious to ask - was your PCB stack really really tight to remove from the back end of the enclosure? Honestly had muscle cramps as the width of the PCBs were so tight to slide out.

Mine just slide out without any force at all, just removed back panel and both PCBs immediately pop out hanging by the flex cable.

[mon2]

@jdoe - also order a long version of the flex cable that mates to the potentiometer. It does not hurt to do so.

The other idea is to carefully remove the nut holding this potentiometer to the front plate so it can be removed as you slide out the PCB stack.

From the last review which has been a while - that flex cable was also very short and will be difficult to put back together. I suppose you can just remove the potentiometer pcb and put it together outside and then slide in the assembly as a whole. A few ideas here.

If you are re-flashing the original flash SMD device on the audio board, be sure to force the CPU RESET line to be LOW so that the XMOS CPU is tri-stated.

See attached diagrams share from SMSL for this repair project.

So you will need to GROUND the TP202 test point. This will then force the XMOS CPU to tri-state when you power up this audio device and release the SPI eeprom lines so you can assert your external programming lines to erase / write / verify the new firmware.

Do not feed your power rail from the programmer back to the audio board; only a common ground.

PS: I think you know exactly what to do but this post is more for future readers with the same issue.

reset.jpg

SPI.jpg

[jdoe]

Hi mon2, thanks a lot for the clarifications! Btw, I wanted to double check the firmware which I have on my side. Here is MD5 checksum of bin file: 36316dbd38d2c5930e9d6a602fd1752a. Could you please verify if this is the correct one?

[jdoe]

Hi mon2! Thanks a lot for the quick responses and help regarding M500 reflash process. I was able to successfully complete it, here are few images:


After reflashing I was able to successfully assemble unit back and update to the latest 2.06 version:

In order to avoid any possible damage for the rom chip I've used Rose's alloy (melting point 90C) to de-solder it.

[mon2]

Thanks so much for the update. Good to know. A few have followed the same procedure with success.

Reviewing the use of s/w to fix the same but it is a difficult learning curve to understand but have not thrown in the towel.

Would you have a flash memory dump BEFORE you did this erase / reflashing of your SMSL box? If yes, would you please post it here or you can send to me through a private email?

Studying the dumps for a resolution.

Thanks and Happy New Year!

[jdoe]

Hi mon2, I've replied to your email with attached rom before update.