Convert JTAG pins to GPIO

Note that you don't need any specialist equipment to do this mod. The picture below shows the iron I used, which has a 3mm chisel tip. In the pic it's the same distance from the camera as R19 - about twice the size of the resistor it's soldering!

1) Don't try to remove R19 - you don't have to, and it's more trouble than it's worth.

2) Heat some solder into the wire you're going to connect. Multi-core is best - the cable below comes from a 40-way IDE ribbon cable.

3) Hold a piece of solder against the right side of R19 where the wire will go, and touch the soldering iron to it (1 sec max). This will break the layer of crud coating the R19 contact and give a better join.

4) Hold the wire against the side of R19 and, from the flash chip side, apply the soldering iron. About 1-2 seconds should do.

5) As you pull away the soldering iron it will probably attract a bump of solder (see picture). Don't bother to try to remove it since it won't do any harm and you'll probably just make the board messy in your attempts to clean it up (well... unless it touches something else metal, of course).

6) Now you have a connection to the right side of R19, you need to connect it via a 1.5K resistor to ground. Depending on which J1 holes you are using for other things you may be able to simply connect to pins 6 or 7 of J1.

Alternative approach

The above, flying lead, is handy if you want to be able to switch back and forth between JTAG and GPIO function for the pins. If you know you'll only want to convert to GPIO and are unlikely to need to use JTAG afterwards, you can try the following.

Take a 1.5K resistor and trim the leads as below, but leaving a little extra wire on the left-hand lead. Strip some bell wire and use the insulator to insulate the leads. You might get away without this, but it's safest to protect them. Solder the right end to the GND connector on J3 (far right pin), then carefully trim the left lead so it's exactly level with where it has to meet R19. This should make it easy to get a tiny blob of solder connecting the lead to R19.

Alternative approach 2

See here

Alternative approach 3

I wanted to be able to easily switch back and forth between JTAG and GPIO modes, so this the approach I took...

I chose to use a 3-pin header rather than a 2-pin header, so that I could always leave the jumper in-situ. I used a 1K resistor rather than a 1.5K as that was all I had to hand, but it works fine.

JTAG mode in left picture, GPIO mode in right picture.