Easy to build Pi Zero handheld

[MSP430]

I wanted to have a retro gaming handheld:

• Easy to build
• Cheap
• Enough buttons for PS1 but no analog sticks
• Pi Zero (2)
• Headphone jack with good sound
• Relatively small
• No thermal problems and no fan

I thought about the Waveshare Game HAT but decided against. As it is build for full sized Pis, has not enough buttons for PS1 and an analog stick.
In the end I build the handheld myself.

The Pi and the display are only sticked into female headers for easy reuse.

Display choice:
I went with a 3.2" Ili9341 with 320x240 pixels. Ili9341 can be driven by the GPIOs with around 60 fps (https://github.com/juj/fbcp-ili9341) and is quite affordeble. 320x240 is a bit more or exactly the resolution of 8 and 16 bit home consoles (integer scale 1) and is thus perfect for these consoles. It is also the minimal resolution of PS1games. Using only the GPIOs for display and buttons, one sie of the Pi is freed up and the Pi (with small heatsink) can stick out for better cooling.

Sound:
The Pi Zero has no headhone jack (the Pi headphone jack is crappy anyway), but via i2s a DAC module can be connected. I went wiht a PCM5102 and soldered it to my central board under the display.

Display LED and Buttons:
Using te Ili9341 and PCM5102 only 17 GPIOs were unused. I used one of them to enable the display backlight to be able to adjust the brightness using hardware PWM. 14 GPIOs are for the 14 PS1 buttons ("12127.3MM Micro Switch Button" from Aliexpress), one for Hotkey and the last one to select the right PWM from the Backlight. Alternatively this one could be used for Volume control.

Power:
The handheld can be powered using the Micro USB of the Pi. Maybe I build a battery extension later. At the moment I use a phone charger or a power bank with cable.

Casing:
Plywood and acrylic glass, both cheap and easy to work with.

Open tasks:
LED backlight PWM not implemented.
Sound works but is not configureable in Emulationstation. See here for details.

I stole some ideas from here:
https://bytesnbits.co.uk/raspberry-pi-powered-handheld-retro-games-console-project/