Arcade Control Board

I’ve finally got round to posting about the raspberry pi arcade.   I’ve build an ATMega based board to convert all the controls to SPI for the raspberry pi, modded the ada-friut retro arcade library to use the SPI based control inputs and etched a PCB for the control board.

I home etched the PCB using the toner transfer method which I find to be a bit of a pain to get a decent result.  The best way I’ve found is to print on magazine paper, then iron on for 5 minutes and finally run through a laminator four or five times.  Here is the result:-



The board does a few thing.   It has 2 9-Pin D connectors for the player 1 and player 2 controls.   The layout is the same as an old atari joystick (in theory you could plug in old Atari comparable joysticks).   The unused pins on the D connector are used for the extra buttons and the player 1/2 buttons.  The joystick axis connect to analogue inputs on the ATMega to save a few pins.  There is also an input for a coin mech to add credits, at the coin mech requires 12v the board requires a 12v and 5v supply.   The 5v supply goes thorough a regulator so that the board runs at 3.3V (8Mhz) this removes the need for logic level conversion between the board and PI.

The above pictured board had a few issues (it also had a zener for the coin op mech which has been removed).   I put a few jumper wires on the bottom to correct the issues, most of which were due to eagle not connecting nodes so I should probably pay more attention to the ERC check.  An updated design is checked int github at  Here is the populated board connected up:-


The other thing I’ve done is sprayed the cabinet black, added the coin mech and stated to put on the plexi glass:-


Only a couple of more things to finish (bevel and marquee) so will post later in the week with the finished result!



Arcade Controls

The Raspberry Pi arcade now has controls!


The controls have been connected to an Arduino which then uses SPI to connect to the Raspberry Pi.   The following hardware design was used:-


Its important to use a logic level converter for the 5v to 3.3v conversion.

After hunting around for good ways to simulate key presses on the Pi I stumbled across the Adafruit retrogame code which uses GPIO as inputs.   I’ve forked this on github and changed it to request the state of the buttons over SPI and update the presses.  It currently polls and doesn’t seem to be using much CPU, although it would be possible to use a separate GPIO pin to tell the Pi that there is a change in state.   The code is available at   This also includes the Arduino code to connect the inputs too.

The SPI protocol basically send an 0xFF command to the Arduino which returns 3 byte, which are P1 status,P2 Status and Aux Status.   The Aux status is used for P1/P2 button and the coin mech.

I’m currently building an input board to replace the Arduino which is basically the ATMega broken out with some connector for P1/P2 and aux.   I’ll publish this at the end of the week.

I also added some audio amplifier and speaker this week.  There is still a bit to do on this project such as getting some artwork printed, painting the cabinet and fixing up the monitor mounts!



Raspberry Pi Arcade

I been considering build an table top arcade cabinet for a while.   Since I’ve had some spare time lately I decided to start a project to build one.  I wanted to use as much stuff that I had around to keep the cost down so I decided to use a Raspberry Pi for running Mame, an old VGA monitor, some spare particle board and an old ATX power supply.  I’m also keen to have the potential to change to a JAMMA board or old PC in the future.

For the cabinet I looked at a few internet designs (weeCade and some others) but decided in the end to just create a rough sketch in 123D and build based around the size of the monitor I had.


The next thing to do was to order in some arcade controls.   I used and ordered their $30 bundle and a $17 coin mech.  I fitted a one player control board to just get things up and running.   I also needed to get a HDMI/VGA converter which came from ebay.   For audio I’ve used a cheap 1W amplifier kit and two 1W speakers.  


Time to wire the Pi up with the monitor and audio and have a quick test.   For the test I have not wired up the control surface so wss using a keyboard.   The Cameleon Pi distro has Mame installed so it was pretty easy to get up and running.   I had to changed the HDMI mode to 2 in the /boot/config.txt which fixed the audio out (from the HDMI adaptor) and as I was change the config I also increased the over clock to 1Ghz.   At this point everything seems to be working apart from the controls!ImageImage


The test control surface is built but not interfaced to the Pi.  I’ve had a few ideas on ways to do this:-

  • Buy a USB keyboard control surface interface.   There is some boards available for this purpose or the other option was to try and make one from an old donor keyboard.  I don’t have a donor keyboard and I didn’t want to buy the convertor.
  • Interface the controls directly to the GPIO on the PI.   This was my original though cut to it being reasonably simple however there is a limited number of pins.  For a 2 player, 3 Button controller with P1/P2 buttons and coin mech I’de need 17 inputs.
  • Using an IO expander IC on SPI.  This wasn’t a bad idea but I need to order in some expander IC’s…
  • Use an Arduino to control get the inputs and convert to SPI.  This is option I’m going to go with as I have all the parts.   I am short one input as I am using an UNO so will put the coin mech either on a Pi GPIO or make it use the same as P1/P2 pressed together which would also allow adding credits without using coins an alternative would be to use multiple inputs on one analogue input using a resistor network.  Using the Arduino also has the advantage of allowing extra features easily (such as auto fire) and has analogue inputs if required.

As I chosen to run with the Arduino solution I’m currently doing a little research on how to get SPI working between Pi/Arduino which I’ll post on once working!

I’m also looking to get a backing printed for the control surface which I will then cover with some clear plastic sheet.



Back from Holiday!

I’m back from holiday and have updated the gate opener code.  I’ve changed my github username so the code is now at   There is a few changes:-

  • Added an iOS client.  This is pretty basic (no design) but has a button to open and a geo-fenced area to allow the opening to happen automatically as you get near to the gate.  In the setup you can add the shared secret for the Arduino and set the centre of the geo fence.  The fence is set to 8 meters at the moment but I’ll look to add a slider to widen this in the future (a non round geofence would also be cool).
  • Fixed up the Arduino code.   On review of the Arduino code today there was a lot of issues.  These included invalid checking, not reading the post parameters correctly and few other issues.   I’ve fixed these up now however the code needs tidying up.  The code was originally based on the example web server for the Arduino Ethernet shield which I think has caused some issues, if I have some time I’m going to re-write from scratch…..

I’ll post the hardware pictures in a future post.


Gate Opener

I’ve posted a new project to github (   The aim of this project is to make my driveway gate open as I drive up to it.   It works by using geo fencing on my phone to detect that I am close to my house and then send a message to an Arduino with ethernet shield to open the gate.   The opening it self is done with a spare gate remote that has had the switch replaced with a MOSFET.   This project is still in progress.

The key thing about this project was to make sure that only some one with a correct code can open the gate.   To do this there is a few steps:-

  1. Both the Arduino and the phone have a shared secret key
  2. The phone requests a token from the Arduino
  3. The token is appended with the command (‘open’ string) and an HMAC digest is created with the token
  4. The digest is sent as a POST parameter to the Arduino
  5. The Arduino re-creates the digest and verifies the received digest matches
  6. The gate is open (sends a 500ms pulse to the MOSFET gate to open the switch).

The above scheme should prevent any replay attacks as all of the requests are unencrypted (there is no SSL for Arduino).    There is also a test Python bottle server and test bash scripts to test both sides of the communications (in the webapp folder).

There has been a few issues with the MOSFET circuit which I will fix in the next few days and post!

LCD Display with Backlight

There is a tutorial and code on the Arduino site on how to  use a 74HC595 shift register  to control a LCD Display here  The Garden Station project uses a modified version of this library which adds the facility to add a second shift register for a second set of outputs, which I used to control the LED statuses.  I’ve also used the QC pin to control the backlight via a MOSFET.   As part of this I added a few extra methods (void setSecondPins(uint8_t secondPins),backlightOn() and  backlightOff() ).   The code is checked into github:-

The garden station code has also been updated to use this code.



I ordered a USBtiny a few weeks ago from ebay to use to program the garden station and it arrived today!


Got it up and running an it works great!  I was previously using a spare Arduino Uno board but this new programmer is simpler and doesn’t require a bunch of jumper wires via a bread board (also frees up the Arduino for something else).   The power also seems to work to power the board via the programmer.

I had to bend back the spare data pins on the prototype board (they were right next to the ISP pins), however I’ve already moved them on the SMD version of the board.