MIDIfying Conn 642, some help please!

[DaveKennett]

Hello all!  I’ve been lurking around for awhile, and I have learned much.  Thanks to all of you who so generously share your time and talents.  I THINK I know what I need.  But I still have some questions, so here goes.

I have been playing with Miditzer 216, and have decided to try to interface it to an old Conn 642 theater organ (two 61 key keyboards, 25 pedals, one expression pedal) with midibox. I would like to leave the organ intact.  There is a 30v supply in the organ that is switched to transistor keyers through the keys.  My plan is to use that voltage through a 56k resistor from each key, which would form a voltage divider with the 10k resistors on the DIN board, putting about 4.6 volts on the inputs.  It appears that those 10k resistors can be configured as pull-DOWN resistors, with the input logic reversed on the DIN board.  Is this true?

Assuming the above works for the two manuals, the pedals are another story.  My plan is to use reed switches and magnets on each pedal, thus completely isolating midibox.  I think I can add a 10k pot to the expression pedal for isolation as well.  Does anyone have a good source for the reed switches and magnets?

It looks like a CORE module and 4 DIN boards will handle the keyboards.  Can an AIN board be configured to handle the expression pedal, as well as the 25 pedals as digital inputs.  This would leave some inputs from the AIN module, as well as the DIN modules to someday be configured as pistons (presets under the keyboards?).

I plan to order kits from SmashTV.  Can all this be connected to one CORE? (With PIC18F452?)  If I need two COREs, should I get different addresses for the PIC ID header?  If I use two COREs, can I merge the MIDI in one of the modules?  It seems I should have an LCD display for setup.  Is two row alphanumeric sufficient?  Can a cable connect directly to the display?

At this point, I’m simply trying to order the right stuff, and any suggestions would be greatly appreciated.  I’m sure more questions will arise.  Thanks again to all those who contribute so much to this forum!

Dave

[nILS]

Hiya Dave, welcome aboard!

I don't know the answers to all of you questions, but I'll try to answer the ones I know the answers to ;-)

It appears that those 10k resistors can be configured as pull-DOWN resistors, with the input logic reversed on the DIN board.  Is this true?

Yes.

Assuming the above works for the two manuals, the pedals are another story.  My plan is to use reed switches and magnets on each pedal, thus completely isolating midibox.  I think I can add a 10k pot to the expression pedal for isolation as well.  Does anyone have a good source for the reed switches and magnets?

There are some threads about this topic somewhere. Hopefully someone can answer that question.

It looks like a CORE module and 4 DIN boards will handle the keyboards.

4 DINx4 boards will give you 4 * 32 = 128 digital inputs. How many do you need?

Can an AIN board be configured to handle the expression pedal, as well as the 25 pedals as digital inputs.  This would leave some inputs from the AIN module, as well as the DIN modules to someday be configured as pistons (presets under the keyboards?).

I am pretty sure this would work, but I doubt it'll be necessary. The Core can handle up to 8 analog inputs w/o the need of an AIN board. So if 128 digital inputs is enough, you're all good. If not, it might be preferable to hook up a part of the digital inputs as a matrix.

I plan to order kits from SmashTV.  Can all this be connected to one CORE? (With PIC18F452?) 

Yes.

It seems I should have an LCD display for setup.  Is two row alphanumeric sufficient?

Yes. 2x16 should do for most test purposes. IMHO Bigger is better though. Debugging is simply more fun with a bigger display ;)

Can a cable connect directly to the display?

Yes and No. This really depends on the pinout of your LCD, in most (all?) cases you'll need to wire one side (usually the LCD side) manually.

I hope that helps,

nILS

[Per S]

As pointed out by nILS, no AIN is necessary. The standard MIDIO128 application has to be modified to include an analog to digital code section to handle the swell shoes. I have done this to support Solo, Main and Crescendo for the Miditzer. 10K linear pot's wired directly to the core. See the Miditzer forum under Midi Electronics for details.

I have completely midified my Rodgers Trio, see

http://www.midibox.org/forum/index.php/topic,3506.0.html. This was done with the standard stuff, no matrix.

Good luck

[jwillans]

Hi Per S,

I didn't realise that 8 analog inputs can be hooked up directly to the core.  Could you point me in the direction of instructions on how to do this and how to modify MIDIO128 to accomodate?

Many thanks,

James

[stryd_one]

It's in my signature, first link ;D

[jwillans]

I did search before I posted, and looked briefly at the core schematics/specification on ucapps.  I couldn't see anything about the core being able to support analog inputs directly without the need for an AIN module?

James

[stryd_one]

The keyword you're in need of is "mux", and to be precise, "unmuxed"  ;)

[DaveKennett]

Wow, thanks for the quick replies, and for the welcome nILS.

OK, here’s my new list for SmashTV.

One CORE module,

Four DIN modules,

One AIN module,

Assorted connectors and cables.

While I could run the expression pedal directly to the CORE, I would still need 25 DINs for the pedals.  By doing it this way, I could still connect the pedals, with inputs still available for the future.  I would be running both midio128 and midibox64.

Anyone see any problems with this approach?

Oh!  I guess I still need to work out details for a display for setup.

Thanks again for all the help.

Dave

[stryd_one]

You can only run one app at a time, and you're being very adventurous with redesigning the boards etc, but I think you're on track.

Wait around for the organ midification experts to chime in, those guys know everything.

[Per S]

OK, here’s my new list for SmashTV.

One CORE module,

Four DIN modules,

One AIN module,

Assorted connectors and cables.

Skip the AIN module, you won't be needing it. I would recommend ordering one more core (different ID) and one more DIN. This will take care of your manuals (61+61) with a few spares and the second core + one DIN will handle the pedals with a few spares and the swell.

The second core can later be expanded with more DIN's for adding pistons.

Finally, forget the Midibox64. The MIDIO128 is the only suitable application for our purpose.

I recommend that you assemble one core and one DIN on a bench, try it out with the MIDI interface hooked up. If you haven't using the MIOS Studio and some of the other needed tools it's easier to do that before installing in the organ. It takes a little while to get used to.

[Per S]

Could you point me in the direction of instructions on how to do this and how to modify MIDIO128 to accomodate?

Go to the Miditzer forum (www.virtualorgan.com Main menu on the left) and look under Midi Electronics and "Using 3 swell pedals with Midibox". You need to be registred in that forum to see it.

It's all there.

[jwillans]

Many thanks Per S and stryd_one.  I will investigate further!

James

[DaveKennett]

Thanks to all for the informative responses.

New shopping list for SmashTV

Two CORE modules

Six DIN modules

Assorted connectors and cables.

I see that I must order both modules with different device ID, but it looks like as long as I specify a character display, a variety of types will work.  I have seen one specific type recommended, but it was out of stock.  Digi-Key and Mousser have such an overwhelming variety, that my confidence is shattered.  I would appreciate any specific recommendations.

Thank again,

Dave

[jimhenry]

Here's a possible LCD display:

http://www.allspectrum.com/store/product_info.php?products_id=967

Mouser and Digi-Key are usually sort of expensive for LCDs. Pick up an HD44780 compatible 2x16 or larger from a surplus source.

[stryd_one]

If you visit this page Character LCD Controller Chips Supported by MIDIbox there's heaps of info about the LCD IC's that are supported, and right down the bottom you can find an ebay search that finds them all :)

If you're not particular about what kind of screen you want, then it's just a matter of finding the cheapest one you can, that has one of those chips. You can usually find all that in the datasheet PDF for the LCD module.

[DaveKennett]

Thanks to all!

Orders have been placed, and I am waiting anxiously.

As I said earlier, I plan to invert the logic from the organ keys, and change the 10k resistors to pull-DOWN.  I then can tap a 30v keying voltage from the organ through about a 56k resistor (giving just a little less than 5v).

My question is this.  What would be the down-side to increasing the resistor value from 10k to say 27k.  I could then use a nominal 150k to drop the voltage.  The 30v keying buss has fairly poor regulation under varying load, due to a 400 ohm resistor feeding the buss (probably for power supply protection).  I thought this could help when several keys are pressed.  Otherwise, I could probably reduce the value of the 400 ohm resistor.  The inputs to the internal organ keyers are in the order of megohms.

Any thoughts?

Thanks,

Dave