DM2 Arcade Button Mod Wiring Help

**faeruithir** · 11-22-2009, 09:06 PM

Hi everyone,

So i'm trying to see if i could put arcade buttons into my crappy Mixman DM2 controller.... I took the thing apart and just looking at 3 simple buttons the circuit has me kinda confused so i was wondering if someone could give me some tips on this.

So heres a picture of the circuit:

Heres what i THINK the circuit is currently:

Heres what i THINK i should wire the new buttons as:

I'm not sure if those resistors are of any importance.....hmm..
Any help with this would be greatly appreciated!

**jason zenso** · 11-23-2009, 11:40 AM

im wanting to do the same thing to my dm2 as well..

**faeruithir** · 11-23-2009, 11:41 AM

nobody knows anything about button wiring?

**Archies'bald** · 11-23-2009, 12:57 PM

The top drawing is a short circuit. The button wouldn't do anything. It's more likely the resistor is in series with the output connection of the button. I would assume the resistors would have to be placed back in to the circuit as they were taken out. They are probably there to stop led's blowing or something.

**Patch** · 11-23-2009, 01:00 PM

I though tabout doing this to one of my DM2s but chickened out because of this... Have you tried to fit an arcade button onto the scratch pad? Can you get 8 to fit around the pad???

A DM2 with an Arcade Button Mod is basically a MidiFighter with an additional 4 banks, crossfader and jog wheels...

It'd be awesome.

**Fatlimey** · 11-23-2009, 02:01 PM

You're missing a little piece of information here that would make it all clear.

When you connect something to a digital input pin on a microcontroller, the pin has three states: "High", "Low" and "Not Connected" (NC). High is when you have a direct circuit between the +5 power supply and the pin, Low is when you have connected the pin directly to the Ground and NC is when the pin is not connect to anything.

The problem with NC pins is that they are essentially very small radio antennas, picking up everything from Radio and TV signals to random quantum events happening in the cosmos, producing essentially random values that can occasionally generate enough charge to make the microcontroller think "Aha, that pin went high!". That causes things to start sending random MIDI events and being unpredictable.

The resistors you see there are connecting the pin to ground (that's the missing piece of information). This means that if the switch is open the pin gets connected to ground. This is called "pulling down" the pin, and the resistor is a "pulldown" resistor. The opposite can also be done where the pin is connected by a resistor to the +5, in which case the resistor is a "pullup" resistor.

When the switch is closed, the circuit has a quicker way to travel to ground from the microcontroller pin causing it to register as Low.

So, to get a better picture of what's going on you need to find out which wires are attached to the +5 supply, which lines connect to the groun and exactly which side of the microcontroller input pin the switch and resistor are. Then you can tell if it's a pulldown or pullup resistor and design your hack accordingly.

Here's a really gentle introduction. http://www.seattlerobotics.org/encod...97/basics.html

**faeruithir** · 11-23-2009, 03:40 PM

well i found my answer
i just had to solder two wires to the ends of the button then solder those wires to the two little contacts on either side of the touch sensitive part on the PCB. Will post pics soon!!
IT WORKS
so many modding possibilities now!!!!
MWAHAHAHHA

**B.C.Ninja** · 11-23-2009, 03:54 PM

Originally Posted by Fatlimey

The resistors you see there are connecting the pin to ground (that's the missing piece of information). This means that if the switch is open the pin gets connected to ground. This is called "pulling down" the pin, and the resistor is a "pulldown" resistor. The opposite can also be done where the pin is connected by a resistor to the +5, in which case the resistor is a "pullup" resistor.

Ahh the old pulldown resistor, things start to get even more exciting when you start adding my good friend the switch debounce circuit as well, But anyway leave the resistors where they are and simply remove the existing switches and add jumper wires to the pads where the switch used to be, then hook any button or switch that you like to the wires and the mod is complete.

**faeruithir** · 11-23-2009, 04:15 PM

Alright, so here's what i did. For all you people out there wanting to mod your DM2s this DOES work. I just tested it.

In the first picture, you can see a button that i soldered to the PCB with some wire. It's a pretty crappy soldering job i know, but it works for now. The button is a simple black momentary pushbutton switch from radioshack (i didn't want to invest in any arcade buttons just yet).

In the next picture, I'll show you how to connect buttons onto the DM2 circuit boards. After you take your DM2 apart, there will be a number of circuit boards. Unscrew one that you want to mod (i chose the one under the Play, Record, and Stop buttons since i don't use those much so it wouldn't matter if i screw up). Now there will be a bunch of white rubber buttons on. Pull one off and you will reveal a little contact pad. The two end points of this pad is where you want to connect your buttons two ends to. Try not to get any solder on the pad itself. This is hard, and after screwing up once i found alternatively you can scratch the green coating off the copper parts to either side of the end points with a knife and solder there.

Hope this is clear!
I've got so many modding ideas now....
some include:
- making a custom casing
- taking the buttons away from inside the jog wheel and placing them somewhere else so i can have a 7 inch record stuck onto the jog wheels without losing button functionality.
- rearranging buttons in all manner of ways
- replacing ALL buttons with arcade buttons...

the best thing is...the DM2 only cost me 15 bucks...if i screw up, i'll just buy a new one! Man i'm excited!