Tuesday, 11 May 2010

Battlezone with lasers

This is a project I've had simmering on the back burner for a while. Still at the early stages but thought it might be fun to keep track of each step here

A few months back I got a 20kps laser scanner galvo set off ebay with the intention of making my own laser projector and a vision of using it to play some old vector arcade games... particularly my old fave Atari Battlezone. The arcade game bit seemed pretty easy, since you can play BZ on the open source MAME emulator so I thought I could hook into the vector terminal emulation.

I found the asynchronous UART on an Arduino board was not quite fast enough to cope with the data... dropping bits all over the place, so I started looking at a USB conneciton to a PIC2455. As a SourceBoost C user I was not able to find any easy to understand USB CDC (Communication Device Class, a.k.a serial port) implementations for the PIC - so I decided to make my own, leaning heavily on sample code I found online.

Well I finally got to the point where my PIC would connect via USB show up as a COM port and be easy to access from a Windows program. Then I hooked up an 12-bit SPI dual DAC and connected it to the galvo setup and tried the first random hacking into MAMEs vector module.

I didn't expect it to work first time, and didn't! but my impatient hacking did produce some interesting squiggles at about 2 fps. I needed to use a long exposure photograph to actually make sense of it, but eventually I recognised a couple of parts of the display and got quite excited that the concept was proved!

The coordinate handling is obviously messed up and the image is wrapping on itself multiple times, also there is no attempt at blanking yet - so there are stray lines all over. The big job will be to find some way to optimise the render list to stop throwing the galvos all over the place and improve on the 2 fps refresh!

As you can see I have a long way to go!

Here is the plot showing the bits I recognised

Here is an actual MAME screen showing what it should look like

If things improve I will post an update!

1 comment:

  1. It's Chris from Nerd Night/BuildBrighton. If you're still struggling to get USB/HID stuff working, look at Oshonsoft PIC18 simulator. It creates a HID class device for you (and is the best software simulator for PIC programming, bar none!)

    It's nice to see some cool PIC coding going on - not just a whole load of Arduino libraries glued together with a bit of dodgy code ;-)