[sdiy] Problem with Groove Electronics Jupiter 8 interface

Colin f colin at colinfraser.com
Wed Feb 27 22:05:15 CET 2013

> I have here a Jupiter 8 with a Groove Electronics 
> MIDI-Interface, which immediately reboots as soon as it 
> receives any MIDI command.
> The MIDI-Out works fine, the MIDI-Thru works (of course as it 
> is "hardwired"), I can set up the configuration of the Groove 
> MIDI via the
> JP8 buttons, but as soon as I send any MIDI information into 
> the interface (no matter what kind of data) the synth reboots.

Are you sure you don't have a MIDI loop ?
The Groove interface is very crashy if presented with too much data. Mine
would guarantee to lock up if I sent it pitchbend from certain synths, but
only because they were sending messages too quickly.
If you don't send it what it doesn't like, you don't lose all your patches.

> Were there different versions of the interface for different JP8s?

No. There's a diagnostic test at boot time that checks the DAC. The routine
can detect whether a 12 or 14 bit DAC is installed, and adjusts to suit.
The Groove OS is a variation of v3.3, with a double-size ROM D that replaces
the Roland DCB code with Groove's MIDI code.
That version is just as good as the final v3.4 - the only differences are in
the diagnostic error handling.
I have ROM images if you need to check your EPROMs are OK.
Also I swapped out the 3 x 2716 and 1 x 2732 in mine for a single 27C256 and
knocked half a watt off the 5V consumption.

Colin f

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