Hacking Digitech XP series for multiple patches simultaneously.

[Taylor]

I've been wanting to get one of the XP1000 pedals made by Jetpack Mods/Guitar Geek. One thing that I'd really like is to be able to use multiple patches at the same time - having all those cool effects but only one at a time seems frustrating.

I'm wondering what would be involved in editing the DSP code to have multiple patches in series. The idea is not to allow any possible combination through the interface of the effect, which would be very difficult to implement of course, but to simply create new patches using, say, patch 10 and 30 connected in series.

Possible?

[Transmogrifox]

This kind of mod seems improbable.  It looks like this guy just ripped the EPROM and modded it so it can load a different code set into RAM, basically requiring a reboot for each effect.  I doubt the DSP inside is powerful enough to handle all the FX simultaneously. 

It may be possible to "edit the DSP code", but this is more like "reverse engineering".  The only "code" you might have access to is the set of binary instructions stored on the EPROM that is loaded into the DSP RAM at boot time.  You would have to disassemble it then use your noggin to make sense of it all before you could make any meaningful mods to it. 

[Processaurus]

yes, that seems unlikely.  I had wanted to just have different patches available from the different models on one eprom, so you wouldn't have to reboot, but even that seems unlikely.
You can make a space station from the cheaper pedals if you have access to an eprom programmer.  There are arcade game supply places online that sell the obsolete DRAM and can even program eproms from your code:

http://www.diystompboxes.com/smfforum/index.php?topic=58144.msg484181#msg484181

Schematic:

http://ca.geocities.com/lwperreault/DigitechXP100.pdf

How to piggyback eproms:

http://www.nerd-out.com/darrenk/500W/DualBoot_piggyback.htm

My solution was just to get get a couple of them and mod each one, then you can get effects in series the old fashioned way!  It's gotten kind of hard to find those pedals cheap, you have to fight Jetpack if you bid on ebay, ha ha, he (or she?!) always wants them more than me.

[SeanCostello]

I doubt this would work. People who design hardware DSP devices tend to use every spare cycle of the available DSP - otherwise, they could have got by with a slower and cheaper DSP processor. There are probably one or two patches in a given box that only use a fraction of the cycles (like a simple ring modulator or echo), but the rest of the algorithms are probably complicated enough that they wouldn't work with even the simple algorithms.

Sean Costello