GP32 JTAG Cable.

My GP32 are all broken! The BLU+ can still run a few of the smaller executables but not reliably, and often with corruption to text and graphics on screen.

The cause of these problems is a small memory module that goes bad extremely easily. The module is used to hold the bios/os for the device and it was always a very handy feature that this could be re-programmed easily. The GP32 has several really good alternative operating systems that make it more useable, but it seems this memory chip is a bit too volatile and just erases or corrupts the data over time.

The source code for re-flashing the bios was made available on, a website that can only be viewed on the wayback machine these days. All you need is a JTAG cable to connect a GP32 to the parallel port of a linux PC, and a fresh bios to flash.

Easy peasy I thought, I'll just google 'GP32 JTAG Cable' and get my credit card ready. I mean, you can buy anything on Amazon these days, right?

So the picture to your right is my prototype JTAG cable for flashing a GP32. The cobbleware website helpfully provides the circuit diagram for the cable but getting hold of the connector for the GP32 end was surprisingly difficult. Despite this I have enough parts to make five JTAG cables, including the prototype.

The naughty memory chip can be replaced with a SST39VF040-70-4C-WHE memory module and then flashed with the JTAG cable so I'll be having a go at using a heatgun on my poor GP32s at some point in the future. At least I've got three of them...

Check out the GP32 link page for all the forum posts and web pages that I found with information about the GP32 firmware problem. If you have a GP32 to fix and want to buy a JTAG cable drop me an email. Based on the amount of work involved to make one of these in 2022 I would say a price of 1 million pounds would be reasonable. I'm up for haggling though.

I'll update this page with my progress, hopefully, very soon.