The general idea is to build a portable console based on a raspberry pi and emulators. I have yet to choose between a Raspberry Pi A+ and Raspberry Pi 2 B. The fist choice will improve compactness, whereas the second one will provide a more powerful system. I may end up building both.
On the software side, i'm using Raspbian, with RetroPie. I managed to use and setup the NeoGeo emulator (gngeo), Snes, Genesis, Master System and NES, with RetroArch.
For those systems, i managed to setup an USB joypad, and even tried 2 players on NeoGeo.
The plan is to use an old SNES gamepad, hacked to use it with GPIO.
I plan on using a small LCD screen. I have tried both a 5" and a 7" one. Both do really well.
For now, i'm working with the 7" for the first prototype. It seems a bit large for an handheld, however the screen is really cool. I will probably try both designs. Both do use the HDMI output.
I also have a 4.3" LCD designed to use SPI, i have yet to try it.
I finished designing the backplate for the 7" LCD from adafruit. It has ears to secure it to the rest of the system. I added reinforcement to make it stiffer, and a cutout for the cable ribbon.
There are standoffs for the LCD's electronic circuit, and standoffs to secure a Raspberry Pi, model A+ or B+.
Here is a rendering of this part :
The green block on the left is the LCD driver, and the lighter green block on the right is a Raspberry pi B+. The blue block beneath is the LCD.
The 6 fixation ears have 3mm holes, to secure it on another part. The plan is to have a border around the LCD on this other part, so it can't move laterally. Then this plate screws onto it, locking it on a vertical axis, causing it to be fixed. Had the LCD had mounting tabs, i would have been able to make a simpler design. But here it is, and i'll print one tomorrow.
I'll design a complementary part in order to enclose this screen so that it can be used on it's own. I'll also design a thicker part to also enclose the raspberry opi, and then multiple parts for the console.
The two LCD's that i'm using for testing purposes are made of the LCD itself, and one or more electronic cards to drive it. The 7" LCD has an HDMI driver, whereas the 5" LCD has the HDMI driver, a touchscreen controller and a small flexible circuitry.
On the 5" LCD, i managed to organize everything with duct tape (and double face one).
For the 7", i can't obtain good results this way. For that purpose, i have begun designing a backplate to hold the circuit in place.
I measured the PCB and made a support, with holes for screws :
It worked properly, i printed one and taped it to the back of the screen with success. However, this was a first step. Now, i'm designing a full backplate, with a fixation for the raspberry pi too, and i will add something on the edge to secure the screen on a frame that i'll design.
It's more expensive, but i wanted to have a tactile screen for some potential uses. Now i'm not so sure about it. It works, but it's not that useful in this project. I wanted to use it on tactile games, but i wonder if i'll use any on this system. However, the tactile layer leaves the possibility to use various kinds of graphic interfaces.