MidiREX -- DIY MIDI loop sequencer


ok, I made further tests :
that’s weird, it work perfectly when running on internal clock.
I tried to sync the midiRex with two differents external clock sources, without result.
I had a look to my midi monitor app and did not find any malformed datas when a note is skipped ; the note message is just missing…


hi there just after a bit of info. i am currently bread boarding a midirex and dont need the foot switch, can i just leave all of that part of the schematic out namely the bat 42 and the two 220ohm resistors.?


Rrright… i have a sick feeling that the problem you’re having is totally related to the fact that it runs on the external clock. MidiREX internal tick is 96PPQN which is 4 times of the incoming external clock, so it’s not a one to one translation.


@kvitekp You mean the MidiREX is looking for a 96ppqn clock to run properly? That’s a bit worrisome. I thought 24ppqn was standard for incoming clock, as all other devices that I have used that sport an internal 96ppqn clock are expecting 24ppqn when on “external”. I know multiplication is a pain, but can something be done about it?


@ParanormalPatroler – of course not, 24PPQN is the standard for MIDI clock so MidiREX “multiplies” incoming MIDI clock by 4, essentially generating 4 internal ticks for each incoming MIDI clock event.


kvitekp - thanks for the explanation.martindunne - it should work even without the 10n caps. If troubles, you can always add a pulldown resistor later…


@kvitekp - you got me scared there for a second!


thanks zardoz all done great bit of kit


cant seem to save anything in eeprom when i record and play it sets all track lengths to 170, all channels to 31 and tempo to 255. any ideas?


@martindunne – sounds like your SRAM is not functioning properly. Try to re-initialize MidiREX by booting it up while holding down switches 1, 3 and 5.


sorry my fault had 24LC512-I/P instead of 23LCV512-I/P. would that be it?


Of course, 24LC512 is an I2C EEPROM chip which is certainly not compatible with 23LCV512 which is SPI Serial RAM with battery backup.


on order cheers


@zardoz do you still have the external clock bug if you record the sequence in external clock mode?


@elektrosamplist yes, in my midiRex, there is still a problem with external clock mode, i fear… I changed my set up so midiRex is the master clock now. Much better…


@zardoz I guess the problem should be the same for everybody…
Does the problem occur in Rec or Play mode? I guess in Play mode…
I may be wrong, but I guess (again) that if you record a sequence while being in external clock sync mode, the midiRex should be OK with replaying it in external clock sync mode.
Again, I may be wrong…


@elektrosamplist yes, problems occurs in play mode.
Weird things happen if I record in external clock sync mode, and replay in same mode.
If I replay the same sequence in internal sync mode, it’s fine.
It would be cool if someone could confirm that issue ; not sure yet if it’s a bug or my build / midi set up…


@zardoz so my guess was not correct
it’s either a firmware bug, or something that you send while in external clock mode that midiRex does not like and makes it skip some notes
another user confirmation would be great
I may build one soon, I’ll check into this if nobody else did when I have mine ready


I believe it’s a firmware bug — will check it out when i’m back from vacations.


Is it possible to transfer a .midi file to midirex? Without recording it from computer to Midirex? I have some trouble syncing my computer’s start and the midi rex start-recording. So there some slight time differences. Thanks.