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Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8312

Posted: 11:54am 23 Nov 2025

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Sometimes I design something just for the pure joy of it. This is one of those. It's unashamedly a gaming machine - probably as close to the CMM2 as I can get using the Pico too. It is intended to be fitted into the Hammond square, translucent blue case so it even has flashy lights to play with. :)

It's pushed along by the PGA2350 module, so you have PSRAM available. Neither GP0 nor GP47 are used so if you have a module that's been modified for GP0 it can still be used.

I decided to forget USB, to remove a processing layer, and use a PS2 keyboard and mouse. It also saves a chunk of PCB area. The downside is that you can't use USB controllers. I also sacrificed the RTC as it needs an I2C port that I can't spare. However, there is space for a ESP8266-01S so you could set the time from a time server.

The game port is very flexible though. This has every data pin reconfigurable in software. My idea is that at boot you can choose which controller you want to use by default and a library routine will set it up for you (it can also be reconfigured by your program). The port can also be used as 7 GPIO pins, GP46 has 100nF to GND though. You can choose:
Atari joystick on GP40,41,42,43 and fire on GP46
NES/SNES on GP41,42,43
As all inputs can be ADC you could use an X-Y analogue stick with several buttons
Both I2C ports on GP42,43 (I2C2) and GP44,45 (I2C) - both 3V3

I'm still undecided about audio. At the moment I envisage stereo down-firing speakers or fixed level line output via the jack socket. However I prefer headphones personally and I'm considering scrapping the line output and using speakers or headphones (via a better quality headphone amp). It's I2S anyway.

A strip of four programmable LEDs is there just for the hell of it and to light the box up. :)

I decided that I was going to use surface mount components where reasonably possible. That's so I can try building it on a hotplate! However, it's all 1206 (apart from a mosfet and the regulator) so quite easily hand solderable.

I think it's one of my better-looking designs so far. :)

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

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