Some documentation

papers/doc/4-instrument/README.md

@@ -22,6 +22,7 @@ depending on the instrument type, there are currently 10 different types of an i
 - [TIA](tia.md) - for use with Atari 2600 system.
 - [AY-3-8910](ay8910.md) - for use with AY-3-8910 PSG sound source and SSG portion in YM2610.
 - [Amiga/sample](amiga.md) for controlling Amiga and other sample based synthsizers like YM2612's Channel 6 PCM mode, NES channel 5, Sega PCM and PC Engine's sample playback mode.
+- [Atari Lynx](lynx.md) - for use with Atari Lynx handheld console. 
 
 # macros
 

papers/doc/4-instrument/lynx.md

@@ -0,0 +1,25 @@
+# Atari Lynx instrument editor
+
+Atari Lynx instrument editor consists of only three macros:
+
+- [Volume] - volume sequence
+- [Arpeggio] - pitch sequencer
+- [Duty/Int] - bit pattern for LFSR taps and integration.
+
+## Audio generation description
+
+Atari Lynx to generate sound uses 12-bit linear feedback shift register with configurable tap. Nine separate bits can be enable to be the source of feedback.
+Namely bits 0, 1, 2, 3, 4, 5, 7, 10 and 11. To generate ANY sound at least one bit MUST be enable.
+
+### Square wave
+
+The LFSR is shifted at the rate define by sound pitch and generates square wave by setting channel output value to +volume or -volume, depending on the bit shifted in.
+
+### Triangle wave
+
+Alternatively when "int" bit is set sound wave is generated by adding or subtracting volume from output effectively producing triangle wave.
+
+#### How triangle wave works?
+
+Hint: To obtain triangle set bits "int" and "11" in "Duty/Int" sequence and set volume to about 22.
+By enabling 11th tap bit the value shifted in is negated after 11 bit is shifted in hence the volume is added for 11 cycles and then subtracted for 11 cycles.