need to build several identical small midi controller. What do I need ?

Design Concepts
1

I need to build for a friend 10 simple midi controller box consisting of 1 joystick and 3 or 4 knobs, probably 2 or 3 buttons and 1 led.

What I want to do is built the box with pots and buttons and connect all the box to a main unit, where the the brain of the controllers will be.

So I was wondering If I could do this with MidiBox ? What do i need ?

would 1 core module be enough ? Can I use 2 AIN modules with demutlipler to reach 64 inputs  ? Or should I rather use encoders and DIN ?

I guess a joystick is analog only and thus need AIN, right ?

1 DOUT would be enough I guess.

Is it very likely that we’ll need more than 10 units in the end so I’m rather going for more inputs than less.

Thanx for your advice !

2

let’s simply look at the single In and Outputs:

DOUT:

10*1 LED = 10 LEDs

A DOUTx1 Board has 8 digital outputs. so in this case a DOUTx2 Board will be the best solution. this will give you 16 digital outputs which are more than enough.

As you cannot buy premade DOUTx2 Boards from Smash or Mike, you can either build it yourself on a vectorboard, etch yourself a DOUTx2 PCB or simply buy a whole DOUTx4 PCB and cut it in the middle if size matters.

more information can be read on the uCApps DOUT page.

DIN:

let’s take 3 buttons per box:

10*3 = 30 buttons

a DINx1 has 8 digital inputs, so a common DINx4 Board will be the best solution as it offers you 32 digital inputs. If 32 are not enough, just add another DINx1 , x2, x3 ,…

more information can be found at the uCApps DIN page

AIN:

let’s take 4 pots and 1 joystick.

one joystick has 2 axis -> so it needs 2 analog inputs (one for x and one for the y axis)

makes a total of 6 analog inputs for one box.

10*6 -> 60 analog inputs needed

so you’ve got to use 2 AINx4 boards which will give you a total of 64 analog inputs.

AFAIK one Core can only be connected to a maximum number of 2 AINx4 boards. But I’m not sure about that

In case you need more than 64 Inputs you’d have to connect them to a second Core and somehow merge the midi signals of the 2 Cores.

If you’re unsure about something, then READ uCApps and the WIKI !!! 

regards

3

Thanx for the reply, you confirm my assumption.

1x core, 1x DOUT4, 1xDIN, 2xAIN and that’s it I guess.

4

First off I thought I should make sure you know you’re not allowed to sell these (nor is your friend)…

As for the design… if the cables between your controller boxes and your brain are too long, you will have problems… What length did you have in mind? It may be easier to make every unit a separate controller, and use 1 core per unit, nothing else, pots/encoders/buttons connected direct to the core.

5

The box are not for selling but for educational purpose (class for kids to introduce them to sound and video manipulation)

We’d rather have one brain so it reduces soldering, costs, need of one power supply and no need for a midi merger box.

What is the length we can use ? I thougth about 5 meters from one box to the brain ?

6

Oh that sounds awesome!! Nice one man!!

Ouch 5 metres… I think you’ll get a fair amount of interference over such a distance. 1m would probably be as far as you’d go. There have been threads in the past about how to work around that though, but you’d definitely get a jump in parts count. Given the inexpensive price of smashtv kits, or maybe you could DIY etch a cimo core, it may not be worth it.

No need for a merger if you chain though… and that could be more flexible in design, physically speaking (suitable for rows of desks as well as a circle on the floor or whatever). Also, maybe you could send power down the spare pins on the midi cable, you won’t need much to drive a few pots (and I assume no LCD).

What a fun thing. Rock on!!

7

Is there a way to ‘amplify’ the signal, by putting some line driver, amp or something in the box or on the brain box ?

If I go the one box one core way I’d still need 1xDIN and 1XAIN, I can’t connect the pots, button and joystick to the core directly, or can I ?

By chaining you mean connecting the cores together or merging one midi out to one midi in ?

8

Is there a way to ‘amplify’ the signal, by putting some line driver, amp or something in the box or on the brain box ?

Yeh that’s the first part I was talking about… It  has been mentioned before sometime I’m sure… See what you can find.

If I go the one box one core way I’d still need 1xDIN and 1XAIN, I can’t connect the pots, button and joystick to the core directly, or can I ?

No you don’t because yes you can :slight_smile:

By chaining you mean connecting the cores together or merging one midi out to one midi in ?

I mean traditional midi cabling, out to in , out to in,  etc etc… onl software merging :slight_smile:

9

Yeh that’s the first part I was talking about… It  has been mentioned before sometime I’m sure… See what you can find.

Line driving is helpful, but only really for digital signals, not as much use for analog.

One core per box would be really the best way to go here. You won’t need DINx4s or AINx4s (as stryd said).

Edit: Just to clarify, line driving can be useful for analog signals, but not at such a low frequency as we’re discussing here.

Line driving for analog signals of audio frequency and higher is done frequently.

10

Just a suggestion here, are the kids of a “soldering age”? You could combine it with their DT class and get them to make the boxes themselves.

The chainable idea is good as it means you can always expand to more units later on.

11

Ok, thanx for the replies.

I guess we’ll go the one core one box way then. I’ll figure out if I can use midi pin to drive power.

I still haven’t found how you can connect 1 joystick, 4 pots and 4 buttons to the core directly without any DIN or AIN. Can you explain it ?

I search the wiki and forum and didn’t find an description.

Also this is not my first midibox, I built a complete CS Midibox SID two years ago (seems far now  :P) so I have some basic knowledge of the things going on, but not clue about direct connections…

Just a suggestion here, are the kids of a “soldering age”? You could combine it with their DT class and get them to make the boxes themselve

I doubt they are. Probably age 7 to 10.

12

You can connect up to 8 analog inputs directly to J5. 8 analog inputs >= 4 pots + Joystick. And since you don’t need an LCD or anything else, there’s plenty of unused io pins on the pic to be used with the 4 buttons. 2 of which could be connected to the 2 analog inputs that are still open.