ICADE RASPBERRY PI MOD

source : http://elecdrome.com/icade-raspberry-pi-mod/

ICADE RASPBERRY PI MOD

Hardware

Display:
HDMI 10.1″ 1280×800 IPS
https://www.adafruit.com/products/1287
Computer Hardware:
Raspberry Pi (Model B) + SD Card with Raspbian Wheezy Installed
http://www.adafruit.com/products/998
http://www.adafruit.com/products/1121
Coin Slot Hardware:
Used a cap-touch sensor to simulate coin drop.
http://www.adafruit.com/products/1374
Other:
USB Hub
Cheap-O USB Powered Speaker
Sintra board used for LCD bezel and back cover
Various mounting hardware I had lying around

Mounting the Raspberry Pi

To mount the Raspberry Pi (RPi), USB hub, power supplies and speaker, I used some 3/4″ thick pine boards I had lying  around.  Cut them to length and screwed into the back of the iCade cabinet. I also removed the USB hub’s enclosure to make sure it’d fit with the back panel on.  I used plastic wire mounting clips to keep all the wiring neat.  The space between the pine boards was used as a channel for the bulk of the wires (HDMI, USB, power).

I used some “modified” plastic spacers for mounting the RPi to the pine boards.  The Pi had to be mounted on an angle to allow the 1/8″ audio cable to squeeze in.

Power Supply

I wanted to be able to power the cabinet without needing an AC/DC power supply external to the cabinet.  To accomplish this, I used an old 120VAC toggle switch I pulled from an old piece of audio equipment and wired in an extension cord to supply power to the cabinet.  Inside the cabinet, I simply plugged the USB hub’s and LCD’s wall wart power supplies to the extension cord.  The USB hub supplies power to the speaker and the RPi.

Mounting the LCD

To mount the LCD I used some pine boards and some spare MDF board as riser/spacer.   The MDF allowed enough space for the the LCD connector needed to connect the LCD panel to the driver board (seen between the pine boards).  The DC power and HDMI cables were run between the pine boards and fished through the the existing cutout used for iPad charging in the iCade’s past life.

Ran the LCD monitor switch panel wiring over the top of the cabinet.

I mounted the LCD monitor adjustment buttons on the back-side of the cabinet.  Once adjustments are made, access to the buttons are not needed again, so not a big deal that they get covered by the back panel.

I added a USB extension cable to allow the connection of a USB flash drive, mouse, keyboard, etc.

Originally, the iCade cabinet had a channel for running a cable to charge the iPad during play.  I reused this channel (with some minor modifications) for running the LCD’s HDMI and DC power cables.

Cut out on joystick panel for LCD cabling (don’t worry, bezel covers up this ugliness).  Square button was added as a dedicated “escape” input to allow user to exit current MAME game.
  
LCD mounted.

Used some spare Sintra board I had for the LCD bezel.  Made the cutout using a utility knife, however, using the Dremel would’ve probably worked out a little better.  Lightly sanded the surface and then spray-painted it black.

Joystick and Buttons Wiring

To connect the control panel (joystick, buttons) to the RPi I decided to ditch the Bluetooth HID board that came with the iCade and wire the switches in directly.

Cut one end of a 26pin ribbon cable to connect up joystick and button inputs to the RPi.  I separated each conductor of the 26pin cable, pulled them all through old DC power plug port.  I had enough slack in the cable that it wasn’t too difficult to solder the wires to the protoboard in this fashion. I used external pull-up and current limiting resistors to interface the buttons with the RPi’s GPIOs, although, I probably could’ve just used the internal pull-ups and been fine.  Here’s a good intro to interfacing your RPi with buttons/switcheshttp://www.cl.cam.ac.uk/projects/raspberrypi/tutorials/robot/buttons_and_switches/

GPIO Mapping Table

To make everything fit nice, I cut the protoboard to the same size as the originally installed Bluetooth HID board.  I kept the layout of all the switch inputs the same (just used 0.1″ headers) which allowed all the button and joystick connectors to mate perfectly.  The red & black wires provide power to the cap-touch sensor.  The blue & white wire pair closest to the right side are the GND and  OUT signals from the cap-touch sensor.  The cap-touch sensor acts like a momentary switch with an active high output.  The blue & white wire pair on the left side of the protoboard connect to the square button on top of the control panel (the “escape” button I mentioned earlier).

Bottom view of the cabinet with all the cables.

Coin Slot

  
For the coin slot I decided to go with a cap-touch sensor to simulate the coin drop.  Found the AT42QT1010 based sensor module from Adafruit, it fit perfectly in the coin slot cut-out.  I removed the original LED board, and just crazy glued the cap-touch sensor module to the plastic, 25 cent cover.  Looks fantastic and lights up when you touch the sensor.

Software

I’m running Raspbian Wheezy on my RPi since its what came preinstalled on the SD card I purchased.  I went with MAME4ALL (https://code.google.com/p/mame4all-pi/) since I heard it was optimized for the RPi.
To map the GPIO inputs to keyboard keys, I used Adafruit’s retrogame utility (https://github.com/adafruit/Adafruit-Retrogame).  To work with my setup, I needed to make a few modifications to “retrogame.c” though.  Since I used external pull-ups for my button inputs, I simply commented out the section of code that enabled the internal inputs (lines 194-214).  Also, the IO table needed to be updated to map all game buttons, joystick inputs, escape button and coin slot inputs.  Here’s my modified version of the table:

struct {
    int pin;
    int key;
} io[] = {
// Input Output (from /usr/include/linux/input.h)
    { 3, KEY_LEFT },
    { 8, KEY_RIGHT },
    { 2, KEY_UP },
    { 4, KEY_DOWN },
    { 9, KEY_LEFTCTRL },
    { 10, KEY_LEFTALT },
    { 22, KEY_1 },
    { 17, KEY_2 },
    { 23, KEY_5 },
    { 18, KEY_ENTER },
    { 25, KEY_ESC },
};
#define IOLEN (sizeof(io) / sizeof(io[0])) // io[] table size

Since the cap-touch sensor (connected to GPIO23) is active-high, the code needed to interpret it differently since all the other GPIO inputs are active-low.  Otherwise, the coin-drop will constantly retrigger.  Replace line 226 with the following code:

if (io[i].pin == 23)
    pinConfig(io[i].pin, "active_low", "1");
else
    pinConfig(io[i].pin, "active_low", "0"); // Don't invert

I can’t remember if I needed to modify mame.cfg for MAME4ALL, here it is just in case:

[config]
artwork=yes
samples=yes
antialias=yes
translucency=yes
skiplines=0
skipcolumns=0
beam=1.0
flicker=0.0
gamma=1.0
frameskip=auto
ror=no
rol=no
flipx=no
flipy=no
samplerate=44100
volume=0
cheat=no
vector_width=640
vector_height=480
kioskmode=no
force_stereo=no
# Anti-alias the display?
display_smooth_stretch=yes
display_border=0
# display effect postprocessing: 0 none, 1 scanlines
display_effect=0
[directory]
inp=inp
nvram=nvram
hi=hi
cfg=cfg
snap=snap
memcard=memcard
sta=sta
artwork=artwork
cheat=.
rompath=roms
samplepath=samples
[frontend]
#Keyboard controls for frontend only
# Get codes from /usr/include/SDL/SDL_keysym.h
K_START=13
K_SELECT=53
K_LEFT=276
K_RIGHT=275
K_UP=273
K_DOWN=274
K_A=306
K_QUIT=27
#Joystick controls for frontend only
J_START=9
J_SELECT=8
J_A=0
AXIS_LR=0
AXIS_UD=1