Keith

One more question: since I'm not using a lot of the I/O (just one input) and not using the eeprom, do I need to ground the I/Os not used or are there pull-ups enabled on them? Thanks,Keith

Thanks niLS. So even though the micro that is spitting out the MIDI dat is on the same board as the GM5, I still need to opto-isolte, yes? I thought the ground loop type problem was just because of a MIDI cable. My device will be using the legacy MIDI on a Mac. So once I plug it in, I suppose I can just fiddle with the J8 jumper and see which setting responds. Before your response, I was going to go with '110' and let the output 'hang'. So you coming up with the same idea just confirms that. Thanks again, Keith

Okay, figured out J6. Still unsure about J1,2,3 configuration for my purpose. And not still not sure what the distinction is between midibox.org configuration and polytec.com configuration (jumper 8) To opto-isolate or not.

I'm using the GM5 to simply input some monophonic, MIDI data (no 'MIDI out') from a microprocessor. Is it really necessary to opto-isolate this stream into the chip? I'm using the MidiBox schematic as a reference. Also, the jumpers shown on the midi-box schematic have me a little baffled for my purpose. '1,0,0' (1 I/Os)? Or '1,1,0' ('I only') for J1,2,3. J6 I can't see a reference for. J8 not sure about. Thanks for any help.-Keith

Last I saw there was some GM5s available from a bulk buy. I tried contacted TK as instructed but didn't get a reply. Any sources anyone knows of? Thanks, Keith