gbadev.org forum archive

This is a read-only mirror of the content originally found on forum.gbadev.org (now offline), salvaged from Wayback machine copies. A new forum can be found here.

DS development > Adding 7 extra buttons to the DS using the mic port.

#139394 - NeX - Wed Sep 05, 2007 8:42 pm

Please note that I only wish to look for one button at once. I came up with this idea of using push-to-make switches, resistors and the mic port to add seven extra buttons to the DS, Guitar Hero style. What do you guys (and gals) in the DS homebrew community think? Will it work? Will it blow my DS sky high? What kind of resistors should I use? I'm currently thinking of:

Code:
MIC                    C    D    E   F    G    A    B
|  |                   100R - - - - - - - - - - - - 700R
|  +----------------+-----+-----+-----+-----+-----+-----+
|                    )     )    )     )     )     )    )
|                    []    []   []    []    []    []   []          <-Resistors
|                    )     )    )     )     )     )    )
|                    |     |    |     |     |     |    |
|                      |    |    |     |     |     |    |           <-Push to makes
|                    |     |    |     |     |     |    |
+-------------------+-----+-----+-----+-----+-----+----+

_________________
Strummer or Drummer?.
Or maybe you would rather play with sand? Sandscape is for you in that case.

#139413 - felix123 - Wed Sep 05, 2007 11:35 pm

Do you need a voltage for it to work?
And if you make the resistor 1,2,4,8, etc, you can read more than one button at a time.
_________________
Nintendo DS homebrew on Wikipedia

#139429 - HyperHacker - Thu Sep 06, 2007 3:08 am

There should be voltage on one pin of the mic port, shouldn't there? I'm not sure if the mic works by sending a variable amount of current through the line or by pulsing it, or both, but if it's the former this could work.
_________________
I'm a PSP hacker now, but I still <3 DS.

#139447 - Snuk the Great - Thu Sep 06, 2007 8:06 am

I thought of this once as well, but just to control moonshell, nothing fancy like Guitar hero, but I don't know much about making hardware. So I would like to know how things turn out when they turn out, so I hope you try a bit ;).

#139471 - NeX - Thu Sep 06, 2007 5:15 pm

Felix123: Thanks for your idea. I came up with that too, about lunchtime (UK).
I think it's done by resistance, judging by the lack of room for "pulsing" hardware on headsets that cost ?4. All I need to do now is figure out how much resistance is required.
_________________
Strummer or Drummer?.
Or maybe you would rather play with sand? Sandscape is for you in that case.

#139472 - NeX - Thu Sep 06, 2007 5:42 pm

According to my voltage tester, 2V comes out of the DS's mic port. If I bridge the contacts, the mic input (on Starfox) hits the roof and stays there till I release them. I'll see if I can get a resistor...
_________________
Strummer or Drummer?.
Or maybe you would rather play with sand? Sandscape is for you in that case.

#139473 - KeithE - Thu Sep 06, 2007 5:45 pm

One thing to consider - if you want sound to come out of the speakers then you need to figure out a way to hold the connector in place without using the headphone jack. If the DS senses that something is plugged into the headphone jack, then the sound will be diverted from speakers to the headphones.

#139474 - NeX - Thu Sep 06, 2007 5:55 pm

True. I was planning upon connecting it to big speakers anyway. I have a mic port hanging around. Trying to find that pointless DS headset I had for my b-day.
_________________
Strummer or Drummer?.
Or maybe you would rather play with sand? Sandscape is for you in that case.

#139481 - Lynx - Thu Sep 06, 2007 6:24 pm

information on how microphones work at wikipedia.
_________________
NDS Homebrew Roms & Reviews

#139485 - NeX - Thu Sep 06, 2007 7:14 pm

I appear to have done something. The main mic no longer works - the DS ignores it whether something is in the mic port or not. Not that I used it anyway. Probably a result of blu-tacking connectors into it.
_________________
Strummer or Drummer?.
Or maybe you would rather play with sand? Sandscape is for you in that case.

#139490 - Lynx - Thu Sep 06, 2007 7:57 pm

You probably burned up the pre-amp that the mic(s) are connected to "shoving" 2v directly into it.
_________________
NDS Homebrew Roms & Reviews

#139494 - NeX - Thu Sep 06, 2007 8:29 pm

Whoops. The mic port still works. Just not the one on the hinge.
_________________
Strummer or Drummer?.
Or maybe you would rather play with sand? Sandscape is for you in that case.

#139535 - Mr Snowflake - Fri Sep 07, 2007 8:08 am

KeithE wrote:
One thing to consider - if you want sound to come out of the speakers then you need to figure out a way to hold the connector in place without using the headphone jack. If the DS senses that something is plugged into the headphone jack, then the sound will be diverted from speakers to the headphones.
This could probably be done by pluging a plastic headphone jack in to the the headphones connector. The DS probably sees the headphone present, when current is flowing.
_________________
http://www.mrsnowflake.be

#139543 - sonny_jim - Fri Sep 07, 2007 10:52 am

I believe the "Switch off speakers when headphones inserted" is done through something called "normalling".

This is an example of normalling:
[Images not permitted - Click here to view it]