(update 31.3.2025: "McDSS_esp-idf_v5.1.1.c" works with ESP-IDF v5.4)

McGurk-Covox/DSS/StereoOn1-System (McDSS)

Parallel/LPT-port soundcard using microcontroller. Supports Covox Speech Thing/Intersound MDO, Disney Sound Source (DSS) and Stereo-on-1 DAC.

Thread at Vogons: https://www.vogons.org/viewtopic.php?f=62&t=93225

Parts

• ESP32-PICO-KIT (if other ESP32 is used, modify pins)
• I2S DAC (e.g. PCM5102A/GY-PCM5102 or I2S DAC amplifier MAX98357A)

New wiring (ESP-IDF 5.1.1)

ESP32	LPT (D25)
Covox:
IO18 🟤	2 (D0)
IO19 🟠	3 (D1)
IO27 🔵	4 (D2)
IO21 🟢	5 (D3)
IO22 🟡	6 (D4)
IO23 🔴	7 (D5)
IO13 🔘	8 (D6)
IO14 🟣	9 (D7)
GND ⚫	GND (18-25)
DSS:
IO9 ⚪	17 (FIFOCLK) (Select Printer_) (PC->DSS)
IO10 ⚫	10 (FIFOFULL) (ACK) (DSS->PC)
Stereo-on-1:
IO4 ⚪	1 (Strobe_) (channel select PC->Covox)
	resistor between IO4 and 5V for external pullup (I have 2.15kohm, 4.7kohm might work too)
ESP32:	I2S DAC:
5V 🔴	Vin (use 5V if possible, more stable)
GND ⚫	Ground
IO25 🟢	DATA
IO32 🟡	BLCK
IO26 🟤	WCLK (must be GPIO 0-31)
GND	SCK (if GY-PCM5102)

* = IO9 and IO10 is only usable with ESP32-PICO-KIT (ESP32-PICO-D4) (with ESP32-WROOM-32 use 16 and 17)

ESP-IDF settings

Component config -> ESP System settings:
 CPU frequency: 240MHz (default: 160MHz)
 Also watch CPU1 tick interrupt: off (default on)
 Watch CPU1 Idle Task: off (default on)
Component config -> FreeRTOS -> Tick rate: 1000 (default 100)
Serial flasher config -> Flash size: 4MB (default 2MB)

Links

• https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf
• https://randomnerdtutorials.com/esp32-pinout-reference-gpios/
• https://www.weigu.lu/microcontroller/tips_tricks/esp32_tips_tricks/index.html
• https://www.mischianti.org/wp-content/uploads/2020/11/ESP32-DOIT-DEV-KIT-v1-pinout-mischianti.png
• https://www.mischianti.org/wp-content/uploads/2021/07/ESP32-DEV-KIT-DevKitC-v4-pinout-mischianti.png
• https://docs.espressif.com/projects/esp-idf/en/latest/esp32/_images/esp32-pico-kit-v4-pinout.png
• https://europe1.discourse-cdn.com/arduino/optimized/4X/2/3/1/2319cb54d8691ab1d1ba749b7992710217dcacf2_2_500x500.jpeg
• Adafruit Mono 2.5W Class D Audio Amplifier - PAM8302: https://www.adafruit.com/product/2130
• ESP32 DAC: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/dac.html
• Xtensa® Instruction Set Architecture (ISA) Reference Manual: https://0x04.net/~mwk/doc/xtensa.pdf
• Is ESP32 5v tolerant? https://voodoo.business/2021/05/19/are-the-esp32-and-esp8266-5v-tolerant-yes-they-officially-are/
• https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/memory-types.html
• https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/i2s.html
• PCM5102: https://www.ti.com/lit/ds/symlink/pcm5100a.pdf
• DSS/Covox exclusive games? https://www.vogons.org/viewtopic.php?t=57885
• LPT: https://www.epanorama.net/circuits/lptpower.html
• LPT: https://www.edaboard.com/threads/parallel-port-max-current-sink-output.49356/

Looks like zeropoint is 128 (0x80). Tested with Hocus Pocus (Covox) and Wolfenstein 3D (DSS).

Covox Speech Thing / Intersound MDO / LPT DAC

• https://en.wikipedia.org/wiki/Covox_Speech_Thing
• https://www.vgmpf.com/Wiki/index.php?title=Intersound_MDO
• Covox supported games: https://www.mobygames.com/attributes/attribute/43/
• Intersound MDO supported games: https://www.mobygames.com/attributes/attribute/1860/

Disney Sound Source (DSS)

ESP32

• Cannot use interrupts, they are too slow. Dedicate another core for bitbanging FIFOCLK signal.
• https://github.com/MacLeod-D/ESp32-Fast-external-IRQs
• Use I2S WCLK for unload buffer interrupt
• DAC doesn't work with 7kHz so double samples to 14kHz

Links

• DSS supported games: https://www.mobygames.com/attribute/sheet/attributeId,44
• Miles Sound System (MSS) DSS patch: https://www.vogons.org/viewtopic.php?t=69539
• Disney Sound Source driver for Win3x, Win9x, WinNT 4: http://www.vogonsdrivers.com/getfile.php?fileid=1680&menustate=0
• DSS Programmers Guide: https://archive.org/details/dss-programmers-guide/page/n1/mode/2up
• Reversing the Disney Sound Source: https://www.vogons.org/viewtopic.php?f=62&t=42250&start=140
• DIY DSS: https://www.vogons.org/viewtopic.php?p=474360#p474360
• Vogons Disney Sound Source with FIFO-buffer ICs: https://www.vogons.org/viewtopic.php?p=405296#p405296

DSS checks

• Dungeon Master DSS detection: https://www.vogons.org/viewtopic.php?t=40751
• Wolfenstein 3D: writes 32 samples to FIFO and checks that FIFOFULL pin activates
• Commander Keen in Keen Dreams (KDreams): v1.0 detects DSS. 33 sample interrupts comes trough. Notice: DSS is not actually supported at all in the game.

Stereo-on-1

• 2,15kohm between gpio and 5V. Channelselect signal is very fast (weak) and pullup is crucial for operation.
• Crystal Dream by Triton: https://www.pouet.net/prod.php?which=463 (LPT pin 1)
• Crystal Dream 2 by Triton: https://www.pouet.net/prod.php?which=462
• Inertia Player 1.22: https://www.pouet.net/prod.php?which=29208
• Dual Module Player 3.01: https://files.scene.org/browse/resources/music/players/
• Fast Tracker II (2.09)
• Galaxy Music Player (GLX) v2.12 by Trial: https://www.pouet.net/prod.php?which=73182 (I couldn't get this to work in stereo)
• https://datasheet.octopart.com/PM7528HP-Analog-Devices-datasheet-11801523.pdf
• http://loboris.eu/ESP32/Xtensa%20Instruction%20Set%20Architecture.pdf
• https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf
• Problem in autodetection: after stereo player (iplay, dmp, crystal dreams) DSS-enable signal (LPT pin17) stays up. To get back to normal covox you have to start DSS-program or some other means drop DSS-enable signal down.
• My Covox (Stereo-On-1) LPT Stereo DAC - home made sound card: https://www.vogons.org/viewtopic.php?t=30139
• Covox in Stereo on one LPT Port - LPTSND X2 (Prototype): https://www.vogons.org/viewtopic.php?t=83891
• Problem with ESP32 GPIO reading: espressif/arduino-esp32#4172
• Compaq Contura 430C (486@100MHz) doesn't work with default LPT bios-settings. Set LPT port to EPP in bios settings to get Stereo-on-1 to work.

Misc stuff

DOSBox

[speaker]
disney=true

Dual Module Player (DMP)

dmp -c6 -p378 -s44100 -q song.mod # covox
dmp -c12 -p378 -s30000 -q song.mod # stereo-in-one
or
SET DMP=-c12 -p378 -s30000 -q

FastDoom

• https://github.com/viti95/FastDoom
• You need wad file from shareware or retail version
• To get music (with fx) from Covox/DSS, you need music as raw files. There is OGG-files in Steam version, but you may find some Doom ogg-files with google also. You see filenames and how to convert ogg files to raw files from this script: https://github.com/viti95/FastDoom/blob/master/SCRIPTS/PCMconvert/convert.sh
• PCM Music format is unsigned 8-bit PCM, and supports 11025, 22050 or 44100 Hz frequencies.
• With Covox: Convert ogg to raw in same samplerate as you are selected from fdsetup. Notice that this also affects to minimum memory requirements (whole raw-file must fit to memory at once)

Create utility to get LPT pin 17 (fifoclk / dss power on) to low with DOS debug-command

Press enter after every line (also when there is empty line).

C:\>debug
n pin17.com         ; filename
a100                ; assemble to address :0100
mov dx,37a          ; 37Ah = LPT control pins port
in al,dx            ; read current state from port
or al,8             ; bit 4 high -> pin 17 low ("and al,F7" would get it to high)
out dx,al           ; write new state to port
ret                 ; return to DOS
                    ; end assembler mode with empty line
rcx                 ; give how many bytes to write in cx register
8                   ; 8 bytes to write
w                   ; write file
q                   ; quit