Digiblaster

The Digiblaster is a simple and cheap device which allows the Amstrad CPC to play 8-bit mono sampled audio.

Version 1 was originally designed by Andreas Stroiczek and an article was published in "CPC International" (A commercial magazine for the CPC which was published in Germany) magazine. This version has a logarithmic volume output.

It was redesigned later to give a linear volume output by Joshua/Exodus and this is version 2.

The digiblaster is connected to the printer port, and uses D6-D0 and /STROBE signals. This table shows the relationship between byte written to printer I/O port and signal.

Bit	Signal
7	/STROBE
6	D6
5	D5
4	D4
3	D3
2	D2
1	D1
0	D0

When writing to the printer port, /STROBE is negated by the printer port hardware, so you will need to write the data with bit 7 negated. The delay between successive writes defines the playback rate.

This piece of code shows how the digiblaster is used:

ld b,&EF    ;printer I/O port
.loop
ld a,(hl)   ;get byte of 8-bit sample data
inc hl
xor &80     ;negate bit 7 of data because it is negated by the printer port hardware
out (c),c
..          ;delay
..
jr nz, loop

Schematics

Digiblaster V1 schematic by Andreas Stroiczek.

Digiblaster V2 schematic by Joshua/Exodus