Saturday David and I wasted a good three hours trying to get a Raspberry Pi 4B to boot using power from the 7800 joystick ports.

It didn't work. The recommended power supply for the 4B is 3 Amps. It's power requirement at idle is 600 mA.

I spent a good portion of this evening trying to get the boot time of an RPi Zero W down to something small enough to correspond with a cart change on the 7800. Best I could do was 28 seconds. Not bad considering that I shaved off 32 seconds from the start of the evening.

In order to get the RPi Zero W to boot faster, I'll probably need to hire an embedded systems expert. I'll save that for the future.

So that said, you're probably wondering, did you try powering the Zero W using the 7800 joystick ports? Well... the recommend power supply for the Zero W is 1.2 Amps. Its idle (probably with a monitor attached) is 150 mA.

Unfortunately, the 0W that I have doesn't have any GPIO pins installed, and you need GPIO pins to backpower it. But you know I got curious...

Long story short, I rigged some jumpers from the 7800 ports to the 0W's GPIO pins 2 and 6... turned on the 7800... and well... 

IT WORKED! It powered up just fine, no problems. Wifi was working, I SSH'd to the pi from my desktop while the pi was being powered by the 7800. Bluetooth was on as well, but I didn't test it. My guess is though, it would have worked since the Wifi was working.

Yes, I have video of it, but it's not that impressive. I'll post some video once my Solderless GPIO pin set arrives. It'll be more impressive anyway. I'll play AtariAge Stratogems on the 7800 hardware with an XBox Controller over Bluetooth.

I'm very happy that the 0W worked well while powered by the joystick ports. Makes the whole Bluetooth setup more of a peripheral.

My guess is that a Linux bare metal build will be required in order to get the boot time to a reasonable speed. Which means a lot of the bloat of OS will need to be removed. But that's beyond my skills... and will probably cost me a pretty penny to make it happen.

Of course, there's no reason why a 4B couldn't be used... it's just that it would require a power supply... and cost $45 vs $15. I'm just hoping to make a Pi HAT that maybe other hackers might want to tinker with.