This is reposted from my blog

I've been playing with Pico-8 a lot lately. I've got a small Pico-8 project site to launch soon, but in the mean time I'm more occupied with getting Pico-8 running on things.

Enter Raspberry Pi, and with it the Waveshare Game HAT -- this is a nifty bit of kit. A screen, controls, and battery circuit that you just plug a Raspberry Pi in to, and voila you have a portable games console.

I've got mine set up with Retropie and this works with the Game HAT pretty much out of the box.

Here are the tweaks needed:

Configure the display in your /boot/config.txt

This seems to vary from one Game HAT to another (according to the Retropie forum) but I found that the following config lines worked when added to the end of the config.txt:

framebuffer_width=512
framebuffer_height=384
hdmi_group=2
hdmi_mode=87
hdmi_cvt=512 384 60

Configure the buttons

The buttons on the Game HAT will work if you install the mk_arcade_joystick_rpi driver in ~/RetroPie-Setup/retropie_setup.sh and then edit /etc/modprobe.d/mk_arcade_joystick_rpi.conf to contain:

options mk_arcade_joystick_rpi map=5 gpio=5,6,13,19,21,4,26,12,23,20,16,18

Installing Pico-8

This is straight-forward. First you download the Raspberry Pi zip from your Pico-8 downloads page, extract it to your home directory, and install wiringpi:

# get Pico-8
$ cd
$ wget <your url to pico-8_0.1.11g_raspi.zip>
$ unzip pico-8_0.1.11g_raspi.zip

# install wiringpi
$ sudo apt install wiringpi

Boot to Pico-8 (and Retropie while holding L)

There are all sorts of approaches that people have detailed elsewhere online to launch Pico-8 from the Retropie launcher, but I prefer the approach of configuring this install to be Pico-8 first, and then Retropie only if we're holding the L shoulder button at boot. This took some fiddling, but it's quite elegant:

First, edit your /etc/profile.d/10-retropie.sh, you can do this over ssh and run "sudo nano /etc/profile.d/10-retropie.sh". Replace the contents with this:

# launch our autostart apps (if we are on the correct tty)
if [ "`tty`" = "/dev/tty1" ] && [ "$USER" = "pi" ]; then
        # if holding L shoulder button, start retropie
        if [[ "$(gpio -g read 23)" = "0" ]]; then
          bash "/opt/retropie/configs/all/autostart.sh"
        else
        # otherwise start pico8 by default
          /home/pi/pico-8/pico8 -height 320 -width 480 -splore && sudo reboot
        fi
fi

We're using the gpio command from wiringpi to check the value of GPIO pin 23 (L shoulder button on the Game HAT). If it's 0 (pressed) we launch the usual Retropie autostart.sh, otherwise we default to running Pico-8.

With the Pico-8 command, I'm specifying the output resolution and launching it with -splore to give us a games menu. The "&& sudo reboot" bit means that if you exit Pico-8 using the menu options, it will then reboot the Raspberry Pi so you can get back to Pico-8 or hold L and start with Retropie.

And that's it. If you want to make the most out of this you'll need to have your Wi-fi configured in Retropie.