add readme

README.md

@@ -0,0 +1,28 @@
+## ZX-MultiSound
+Sound card for ZX Spectrum (NemoBus).
+
+[![photo](images/revA.small.webp)](images/revA.webp?raw=true)
+
+[![photo](images/revA-side.small.webp)](images/revA-side.webp?raw=true)
+
+### Tech specs
+* TurboSound FM (2xYM2203)
+* General Sound (12MHz, 1024Kb of RAM)
+* SAA1099 (use port #FF/#1FF to access SAA chip, write #F7/#FF to #FFFD port to enable/disable SAA)
+* SounDrive (ports #0F, #1F, #4F, #5F)
+* MIDI (controlled via YM(AY) chip - compatible with ZX Spectrum 128K / ZXUNO)
+* Low profile PCB: 170x64mm
+* 5V and 12V power required
+* 4x 1-bit digital DACs for GS and SounDrive
+
+### Changelog & current status
+* Rev.A - first release. Please note the [errata](pcb/rev.A/ERRATA.txt);
+* Rev.A1 - fixed all rev.A issues. This revision hasn't been tested.
+
+Sound card has been tested only with ZX Evolution. You can use it with another computer at your own risk.
+
+### Related projects
+* Turbo Sound FM - [link](http://www.nedopc.com/TURBOSOUND/ts-fm.php)
+* ZXM-SoundCard - [link](http://micklab.ru/My%20Soundcard/ZXMSoundCard.htm)
+* ZXM-GeneralSound - [link](http://micklab.ru/My%20Soundcard/ZXMGeneralSound.htm)
+* NeoGS - [link](http://www.nedopc.com/gs/ngs.php)