Mini Ms. Pacman machine made with Beaglebone Black. via Bruteforce
For this year’s Bring a Hack dinner after Maker Faire, I built a mini Ms. Pacman machine.
My goal was to have a playable game in an enclosure that resembled the full size cabinet.
Since I already had a Beaglebone Black sitting on the shelf, I decided to use it for the project.
The electronics are pretty straightforward. It’s a Beaglebone Black with an Adafruit Proto Cape and the 4D Systems Display Cape. I consulted the wiring diagrams for the display cape to see what pins were not in use. I wired up the LEDs for the marquee to a digital pin (via the proto cape) and did the same with the one-player start button. I initially had planned to hook the analog stick up to some unused analog pins, but found that I couldn’t read their values. After some research, I discovered that the touchscreen driver basically monopolizes the ADC on the Beaglebone, so unless I was willing to mess with the driver, I’d have to come up with some physical solution. I thought about slapping in an external ADC, but I ended up just physically modifying the joystick. I cracked open the pots and scraped away the center electrical contact for both left-right and up-down. Then I wired the joystick up as a set of four digital switches to digital input pins. This worked fine.
I was happy to discover I could power the whole contraption (USB audio included) off of the USB input on the Beaglebone. I wanted to make sure it would run all night at Bring a Hack, so I hooked it up to a 15 amp hour battery (for recharging cell phones) and did a test. I let it run for 8 hours, and it only used about a quarter of the capacity of the battery. Nice.
It’s running the standard Debian Wheezy image for the Beaglebone Black. I compiled AdvanceMame on the BBB itself (took ages). I wrote a little python script which turns the marquee lights on during boot with the Adafruit BBB GPIO library – super easy. I then wrote a joystick ‘driver’ in python using the same GPIO library and the wonderful uinput library which creates a kernel uinput device and emits events. I was able to read the digital joystick pins and then emit uinput joystick events. Luckily, AdvanceMame was able to see these as jstick+ and jstick- events and map them correctly within the game. There was a fair amount of fiddling about getting the display positioned and rotated correctly on the screen, and getting the sound stable with AdvanceMame and Linux. I was getting a number of Linux USB stack crashes, which seemed to quiet down once I switched the sound driver to alsa in the AdvanceMame config.
That’s about it. I didn’t take any photos during the build, unfortunately. I’ll upload some more finished pictures here soon.
Each Tuesday is BeagleBone Black Day here Adafruit! What is the BeagleBone? The BeagleBones are a line of affordable single-board Linux computers (SBCs) created by Texas Instruments. New to the Bone? Grab one of our Adafruit BeagleBone Black Starter Packs and check out our extensive resources available on the Adafruit Learning System including a guide to setting up the Adafruit BeagleBone IO Python Library. We have a number of Bone accessories including add-on shields (called “capes”) and USB devices to help you do even more with your SBC. Need a nice display to go along with your Bone? Check out our fine selection of HDMI displays, we’ve tested all of them with the Beagle Bone Black!
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