What is it?

The MSX-EQ PSG Spectrolyzer is a simple cartridge for the MSX platform that visualizes the spectrum of notes played by the programmable sound generator, such as the AY-3-8910 or YM2149 (PSG). The cartridge board is intended for the standard MSX cartridge slot. The board shows the effect of measuring the signal's level, in which each reproduced frequency (or frequencyrange) corresponds to one of 9 vertical LED indicators.

All files of the MSX-EQ project are available in the RBSC's Github repository:

• https://github.com/RBSC/MSX-EQ

Why did you make it?

The MSX-EQ cartridge is based on the PLD Altera EPM7128, that has 128 logical units. The PLD intercepts PSG port I/O, identifies the played note/frequency and displays its representation on the dedicated LED indicator. The cartridge doesn't need any special setup. It can be installed into any standard MSX slot that allows an unobstructed view of the cartridge's LED indicators.
The cartridge visualizes the played notes/frequencies in games and demos in real time. After a note/frequency fades out, the LED indicators automatically switch off.

What makes it special?

The cartridge may be assembled in 2 different ways:

• With discrete LED elements - simple, but allowing various color combinations
• With LED assemblies - the so-called "bars", mostly single-colored

The following color combinations are possible (those were tested and were found suitable for the project, however other color
combinations are possible):

• One color LEDs or LED assemblies: blue, red or green
• Multi-colored LEDs or LED assemblies: blue with red or green with red (red LEDs are placed on top)