How many DIN's and DOUT's are possible?

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Hello -

Goal is to have MIDI  IN and OUT for a church pipe organ (2-61 note keyboards + 32 note pedals +  Stop Action switches)

I bought the MIDIO 128 V3 boards  including MBHP_CORE_LPC17 and 4 DIN kits and 4 DOUT kits  and parts from the guy in Tenessee USA thinking that was the max that could be addressed. 

There seems to be conflicting info:  I read in one place that up to 4 of each (max 128 I/O) ,  but elsewhere it says that in the 32 bit OS that up to 8 DIN's and 8 DOUTS are possible. 

I am just soldering the boards now,  and about to configure the inputs and outputs.  128 is not really enough for a 2 manual + pedal organ.  

I did search the documentation (and found this seeming contradiction) and also searched the forum here to see if my question has been addressed.   I am baffled by how few people seem to be trying to do what I want to do:  to have full MIDI IN and OUT for a 2 manual organ.  

Another issue I have is that the organ uses 12 volt keying and wondering if I'm going to have to build another layer of interface between the DIN/DOUTs and the keying.  

There seem to be some very knowledgeable people on the form that are providing some very helpful advice.  

Thank you in advance. 


WA state - USA






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Hello TOM,

You are embarking on a project that has been explained in depth many times on this forum.  Your statement, " Goal is to have MIDI  IN and OUT for a church pipe organ (2-61 note keyboards + 32 note pedals +  Stop Action switches)" is sort of open ended, allowing a variety of  outcomes. In order to have a better understanding of your Goal, a few questions>

1.  As stated, the instrument is a pipe organ, "pipe" being the key word, and its a two manual instrument with pedals and "stop action switches". 

     >  How many ranks?

     >  Will the midification replace the existing organ relay,  and is the relay integral to the console?  There are a variety of small 2 manual consoles  (Moller Artiste, 3-5 ranks for example)  without a major relay, but  a mechanical system where the key switches activate the pipe pallet valves electrically.   Your course of action is dependent on your intentiion, i.e.,  do you intend to  gut the console and replace with midibox encoders, etc.; augment the existing to allow addition of pipe ranks, or  electronic, sample based ranks,  or to leave the console intact with a midibox overlay to provide a functioning virtual organ, computer based, using jOrgan, Miditzer or Hauptwerk virtual software, yet still have the option to play the organ in its original form.  How you apply midibox DINs and DOUTS and the midio128 V3 app will depend on where you are going with the project. 

2.  "stop action switches"  imply  manual rocker type switches mounted just above the top keydesk, Is this the case, or, are they SAMS, with a set and general cancel button, and combination action? 

3.   You need to read the specification for midio128V3 in the UcAPPs section on the midibox website.  midio128, v3, will provide 128 inputs and 128 outputs Using groups of DINS and DOUTS, which could be enough to midify your console, but again, that depends on what you have, and what you want to achieve.  You are not necessarily limited to 128 i/o, because of the capability of using KB matrix modules of which you could have several increasing the inputs and outputs.  for example, I am running a 3 manual console with pedals, 64 SAMS with combination action (Peterson). The console uses 2 KB matrix modules to encode 3 keyboards, pedalboard and the stop contacts on the SAMs.  This freed up the 128 std DINS   (DIN4X) for pistons, etc., swell shoe s and cresendo pedal.  My organ is totally electronic, no pipes, and uses an LPC-17 and an additional Core8, an Artisan Sound Engine with artisan Samples.  I designed it to be free of a PC, and virtual organ software  (jOrgan, Miditzer, Hauptwerk)  with touch screen monitor, etc.

You also need to look at the newer "NG"  software which can do everything that the midio128V3 can do, plus more.

I will be happy to answer any question you may have, or point you as needed.  in addition,  there are many who have walked the path you are on, and will through in comments as you go.

My suggestion at this point, is for you a be more specific in what you want to achieve in the end.


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I read in one place that up to 4 of each (max 128 I/O) ,  but elsewhere it says that in the 32 bit OS that up to 8 DIN's and 8 DOUTS are possible. 

I'd be interested in the answer to this question also. From what I've read, a maximum of  four DIN/DOUT modules are scanned. I'd like to modify something so that 8 or more modules could be scanned. What would be the consequences of doing this?

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Thanks, John.  I did find the resolution to the conflict:  It is NG that allows 256 ins and outs.  So it looks like I'm going to have to set each keyboard up into a matrix.  That is going to be a formidable job.  It would sure be nice if there was a board for that!  

That was my main question at this point (256 vs 128 I/O).  I am going to spend more time on the forum.  I went thru it from top to bottom before I bought the system and at that time (a couple of years ago)  did not see anybody doing an organ console with MIDI IN and OUT.   I did see a suggestion to "see John's build on this forum"  but with no link or idea on how to find that.  I will dig deeper and hopefully find out more about your project and learn from it.    


If I have more questions then I will post them (and I'll try to put them in the right place!).  

Thanks again for your reply and your offer to help.  




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Well I have spent many hours searching the forum and thought I would find a project similar to mine with answers to the questions I have,  but I will now post some questions and if the answer is already out there please forgive me and just point me to what I should be reading: 

we want MIDI IN and OUT for an existing pipe organ, about 20 ranks:  2 keyboards (61 notes each) and pedals (32) and about 50 stop tabs.  

I have read of many projects where an organ console was converted to MIDI IN for use with Hauptwerk, etc.  But this is a working pipe organ with a 12 volt keying and switching system that we want to keep working.   

I think I understand what is needed to get MIDI-in (please correct me if I'm wrong):  I can use 2803's to convert the voltage (maybe I should be using opto-couplers,  but I'm familiar with the 2803's and they do 8 notes per switch whereas opticals are at most 4 per chip),  and then read in the keyboards as a matrix either using the DIO matrix boards or the MidiBox KB scheme. 

What I do not understand is how to WRITE to a keyboard matrix.   Since the matrix is scanned, it seems that the output values would have to be latched between scans,  or the note would only be on when the scan is active.

John,  I read about your project and you talk about driving your SAM's so I see aspects of MIDI-out in your system.  Is your system both MIDI IN and OUT? 

That's where I'm stuck right now.  I don't understand how to do MIDI-OUT to a keyboard matrix. 

Thanks in advance,




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If the organ is to remain intact and fully playable, then all existing relay functions must remain.  Adding midi in and out means:

The existing organ relay would have to be modified to accept a midi input stream, and also generate a midi output stream.  Accomplishing that brings up many questions, and could be done by several methods, i.e.

     a.   Modify electronically the existing relay to accept the midi in and out, which could be difficult or impossible depending on the design of the relay.

     b.   overlay, mechanically, the key contacts, stop action switch contacts, pistons, swell shoe, such that the mechanical switches operate a second set of contacts that are inputs to a midi system of DINs, KB boards, LPC17, etc., and a PC running jOrgan or Haupwerk which would serve as the midi relay, generating a midi out stream.  It is also possible, if not preferable to output the midi stream directly from the LPC17.

    c.  The third possibility would be to gut the console and existing relay, and replace it with a new system of midi devices which would power the pipe palet valves, and SAMS ( if you have them).  This would be by far the most costly, and complicated.


Of the three choices,  I have done choice b, and c.   In one case with  a pc running jOrgan, and the other with an LPC17.  Both installations provided a standard organ system, no monitor, mouse etc.

You continue to talk about DINS, DOuts, LPC, but its not clear how you intend to apply them.  Does any of the choices match your intent?

Concerning the midi in and out,  Do you intend to play midi files recorded on computer based software?  Do you plan to play on this organ, recording internally the midi messages, then play it back on this organ, what is your intention?  All this has a bearing on the hardware and firmware as well.

Who built the organ?  does it have SAMS rocker tabs or pull tabs,  set button and gen cancel, combination action by peterson, Syndyne, etc.?  Does  the combination action have memory?  Does it have a relay cabinet separate from the console, or is the relay internal to the console?

I will keep going with this, if you could answer my questions.


Edited by John_W._Couvillon

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Thanks for the note John.  It is certainly a bigger job than we thought it would be.  We are working on an electrical interface to the existing keying system,  plan to use NG to get the 256 IN/OUT which is enough for us (but still would not be enough for most theater organs).  At present there is no combination action but have allowed for that possibility.  We are now well into the project and just hoping to have it done by Christmas.  

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