ZX Spectrum as a digital photo frame

Heath Robinson would be proud of this one I think – a digital photo frame constructed from a ZX Spectrum, an old portable TV and an audio cable linked to a Linux box which is the source of the actual pictures. Here’s how it works:

The main software component is a short Python script that does a quick and dirty job of the following:

1. Read an image file
2. Convert to Spectrum screen size (256×192)
3. Convert to monochrome
4. Convert to Spectrum screen format
5. Generate a TZX file with an appropriate header

You can grab a copy of the script here – feel free to extend and improve.

The TZX file is a concise representation of a Spectrum audio cassette, so we need to convert that into actual audio and send it out of the Linux box’s sound card and into the Spectrum. Luckily Erik Kunze’s ZXLink does this part, and is easy to compile and install.

Putting the two together with a simple shell script allows a constant stream of ‘images’ to be sent out of the sound card and into the Spectrum. All that remains is to set up the Spectrum end, which is achieved by entering the following BASIC program:

10 LOAD "" CODE
20 GOTO 10

Because we’ve already set up the tape header block to do it, the image data is loaded directly to screen memory. I plan to come back and improve on this in various ways, but only after I’ve finished putting more old hardware to dubious use around the house. More on that next time.