Had 2 hours this morning to work on the project, and made progress on the Frequency Generator.
Playback frequency can now be set by the external controller, and the end of sample detector is working.
The master Sound Clock is 20MHz, and playback can be set from 0 to 78 KHz, with 16 bit resolution.
How this works...
Dual 74HC590 counters are chained to create a 16 bit counter, which is clocked at 20MHz.
Dual 74HC688 comparators are set to reset the counter at some 16 bit value.
On a reset, the pulse is sent to a set of 5 x 74HC193 counters, setup as a 19 bit counter to the SRAM.
Sample position is set by loading the value into the 193 counters (3 bytes).
End of playback is detected by an output value of 255 from the SRAM into another 688.
The 688 triggers a 74HC74 flip flop to stop the counters.
Here is a quick demo of it working...
https://youtu.be/fuJz3ERi8KgAnd some photos of the ever growing wiring mess that is soon due for a cleanup!...
Added Frequency Generator and Sample End Detector.Although I can run the Sound Generator completely independent of the Video Generator, I like to look at something while I work.
Added a little Tribute to Van Halen, since I shamelessly stole the intro to Jump as a test of my Sample Playback Circuit!...
Thanks Eddy!This part didn't really involve any challenge, as it is nothing but a bunch of slow speed counters and a few logic gates.
The Analog Section will be a lot more fun, as it is much more of a dark art than digital logic!
I will be adding an 8 bit Digital to Analog Volume Control and an 8 Bit controllable Low Pass Filter next.
Both Analog systems will be made of LM358 Op Amps and some discrete components.
Once all of the sub-systems are working, I will build Voice #2 next to Voice#1, with an optimized component layout.
From there, all wiring will be cleanup up, and then the Voices #3 and #4 will be added.
Once all 4 Identical Voices are working, I will add the final dual 2:1 mixer to get Stereo output (Amiga Style).
That's all for a few more days... Cheers!
Radical Brad