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My 7800 Pokey Sound Tool (Pokey Player)


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I don't know if this is useful to anyone else, but I built a tool to help me figure out what pokey sounds on the 7800

It lets me test out sound mixing on all four channels at the same time.


-Joystick/arrow keys select the value to change (orange)
-Left button increases value, right button decreases value

- F = Frequency

-W =Waveform

-V = Volume (needs to be > 0 to hear anything)

-D = Duration (how many frames to play the sound)

-S = Silence  (amount of time between plays to keep channel silent)

-T = Type  (C)onstant (play at same volume), (A)attack (play from volume 0 to 15, (D)ecay (play from volume 15 to 0) 


This is s the first version. Suggestions much appreciated.  


link: JS7800: Atari 7800 Emulator (raz0red.github.io)



There may well already be a tool like this, but this is mine.  I used to help me understand the pokey chip and what it can do.


I think I probably made something similar to this in Atari 8-bit BASIC back in the 1984 or 1985 for the same purpose.





pokeyplayer2.bas.a78 pokeyplayer2.bas.bin

Edited by fultonbot
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Very impressive.


There are a couple of other registers which shape the sound too ...




There are 8-bits to this register.   These control everything from clocking (which can let you play your channels at higher or lower frequencies), hi-pass filter (an effect which lets you use one channel to modulate the waveform of the other), 16-bit mode (joining two channels into a 16-bit one to extend the musical range), and a 9-bit polycounter (for playing musical notes on the $0x and $8x waveform settings).




This one is more complicated.   It acts on the first two channels.  Default is $03.  Storing $8B here activates two tone mode where the frequency of the 2nd channel is played to the first channel, plus a modulation from the first channel.  It was used in the old Atari 8-bit days for cassette I/O.


Both of these have varying issues of compatibility when it comes to emulation, though ...



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1 hour ago, Synthpopalooza said:

Very impressive.


There are a couple of other registers which shape the sound too ...



Yeah, I did read about those, but they stretched my brain too-far to try to implement just yet.   I think once I realize I can't do what I need with the 8-bit Pokey, I'll be on to the 16-bit stuff.

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