%import syslib psg { ; $1F9C0 - $1F9FF 16 blocks of 4 PSG registers (16 voices) ; 00 frequency word LSB ; 01 frequency word MSB. freqword = HERZ / 0.3725290298461914 ; 02 bit 7 =right, bit 6 = left, bits 5-0 = volume 0-63 levels ; 03 bit 7,6 = waveform, bits 5-0 = Pulse width 0-63 ; waveform: 0=pulse, 1=sawtooth, 2=triangle, 3=noise const ubyte PULSE = %00000000 const ubyte SAWTOOTH = %01000000 const ubyte TRIANGLE = %10000000 const ubyte NOISE = %11000000 const ubyte LEFT = %01000000 const ubyte RIGHT = %10000000 sub voice(ubyte voice_num, ubyte channel, ubyte volume, ubyte waveform, ubyte pulsewidth) { ; -- Enables a 'voice' on the PSG. ; voice_num = 0-15, the voice number. ; channel = either LEFT or RIGHT or (LEFT|RIGHT). Specifies the stereo channel(s) to use. ; volume = 0-63, the starting volume for the voice ; waveform = one of PULSE,SAWTOOTH,TRIANGLE,NOISE. ; pulsewidth = 0-63. Specifies the pulse width for waveform=PULSE. envelope_states[voice_num] = 255 cx16.r0 = $f9c2 + voice_num * 4 cx16.VERA_CTRL = 0 cx16.VERA_ADDR_L = lsb(cx16.r0) cx16.VERA_ADDR_M = msb(cx16.r0) cx16.VERA_ADDR_H = 1 cx16.VERA_DATA0 = channel | volume cx16.VERA_ADDR_L++ cx16.VERA_DATA0 = waveform | pulsewidth envelope_volumes[voice_num] = mkword(volume, 0) envelope_maxvolumes[voice_num] = volume } ; sub freq_hz(ubyte voice_num, float hertz) { ; ; this would rely on floating point math to convert hertz to vera frequency ; ; could be replaced by integer math maybe with a lookup table? ; uword vera_freq = (hertz / 0.3725290298461914) as uword ; freq(voice_num, vera_freq) ; } sub freq(ubyte voice_num, uword vera_freq) { ; -- Changes the frequency of the voice's sound. ; voice_num = 0-15, vera_freq = 0-65535 calculate this via the formula given in the Vera's PSG documentation. ; (https://github.com/commanderx16/x16-docs/blob/master/VERA%20Programmer's%20Reference.md) cx16.r0 = $f9c0 + voice_num * 4 cx16.VERA_CTRL = 0 cx16.VERA_ADDR_L = lsb(cx16.r0) cx16.VERA_ADDR_M = msb(cx16.r0) cx16.VERA_ADDR_H = 1 cx16.VERA_DATA0 = lsb(vera_freq) cx16.VERA_ADDR_L++ cx16.VERA_DATA0 = msb(vera_freq) } sub volume(ubyte voice_num, ubyte vol) { ; -- Modifies the volume of this voice. ; voice_num = 0-15, vol = 0-63 where 0=silent, 63=loudest. cx16.r0 = $f9c2 + voice_num * 4 cx16.vpoke(1, cx16.r0, cx16.vpeek(1, cx16.r0) & %11000000 | vol) envelope_volumes[voice_num] = mkword(vol, 0) envelope_maxvolumes[voice_num] = vol } sub pulse_width(ubyte voice_num, ubyte pw) { ; -- Modifies the pulse width of this voice (when waveform=PULSE) ; voice_num = 0-15, pw = 0-63 where 0=narrow, 63=50%cycle so square wave. cx16.r0 = $f9c3 + voice_num * 4 cx16.vpoke(1, cx16.r0, cx16.vpeek(1, cx16.r0) & %11000000 | pw) } sub envelope(ubyte voice_num, ubyte maxvolume, ubyte attack, ubyte sustain, ubyte release) { ; -- Enables AttackSustainRelease volume envelope for a voice. ; Note: this requires setting up envelopes_irq() as well, read its description. ; voice_num = 0-15 maxvolume = 0-63 ; attack, sustain, release = 0-255 that determine the speed of the A/D/R. ; TODO describe how the speeds are calculated. For now, experiment. Higher values means *slower* enveloping. envelope_states[voice_num] = 255 envelope_attacks[voice_num] = attack envelope_sustains[voice_num] = sustain envelope_releases[voice_num] = release if attack attack = 0 else attack = maxvolume ; max volume when no attack is set envelope_volumes[voice_num] = mkword(attack, 0) envelope_maxvolumes[voice_num] = maxvolume envelope_states[voice_num] = 0 } sub silent() { ; -- Shut down all PSG voices. for cx16.r1L in 0 to 15 { envelope_states[cx16.r1L] = 255 envelope_volumes[cx16.r1L] = 0 volume(cx16.r1L, 0) } } sub envelopes_irq() { ; If you want to use real-time volume envelopes (Attack-Sustain-Release), ; you have to call this routine every 1/60th second, for example from your vsync irq handler, ; or just install this routine as the only irq handler if you don't have to do other things there. ; Example: cx16.set_irq(&psg.envelopes_irq, true) ; NOTE: this routine calls save/restore_vera_context() for you, don't nest this! ; cx16.r0 = the volume word (volume scaled by 256) ; cx16.r1L = the voice number ; cx16.r2L = attack value pushw(cx16.r0) push(cx16.r1L) push(cx16.r2L) pushw(cx16.r9) ; calculate new volumes for cx16.r1L in 0 to 15 { when envelope_states[cx16.r1L] { 0 -> { ; attack cx16.r2L = envelope_maxvolumes[cx16.r1L] cx16.r0 = envelope_volumes[cx16.r1L] + envelope_attacks[cx16.r1L] * $0040 if msb(cx16.r0) > cx16.r2L or envelope_attacks[cx16.r1L]==0 { cx16.r0 = mkword(cx16.r2L, 0) envelope_attacks[cx16.r1L] = 0 envelope_states[cx16.r1L] = 1 ; start sustain } envelope_volumes[cx16.r1L] = cx16.r0 } 1 -> { ; sustain if envelope_sustains[cx16.r1L] { envelope_sustains[cx16.r1L]-- } else { envelope_states[cx16.r1L] = 2 ; start release } } 2 -> { ; release cx16.r0 = envelope_volumes[cx16.r1L] - envelope_releases[cx16.r1L] * $0040 if msb(cx16.r0) & %11000000 { cx16.r0 = 0 envelope_releases[cx16.r1L] = 0 } envelope_volumes[cx16.r1L] = cx16.r0 } } } ; set new volumes of all 16 voices, using vera stride of 4 cx16.save_vera_context() cx16.VERA_CTRL = 0 cx16.VERA_ADDR_L = $c2 cx16.VERA_ADDR_M = $f9 cx16.VERA_ADDR_H = 1 | %00110000 cx16.VERA_CTRL = 1 cx16.VERA_ADDR_L = $c2 cx16.VERA_ADDR_M = $f9 cx16.VERA_ADDR_H = 1 | %00110000 for cx16.r1L in 0 to 15 { cx16.VERA_DATA0 = cx16.VERA_DATA1 & %11000000 | msb(envelope_volumes[cx16.r1L]) } cx16.restore_vera_context() popw(cx16.r9) pop(cx16.r2L) pop(cx16.r1L) popw(cx16.r0) } ubyte[16] envelope_states uword[16] envelope_volumes ; scaled by 256 ubyte[16] envelope_attacks ubyte[16] envelope_sustains ubyte[16] envelope_releases ubyte[16] envelope_maxvolumes }