Thursday, July 22, 2010

Make a small CV/Gate sequencer?

This is too much, I know.
But, when you have a CV/Gate-synthesizer, don't you just feel the urge to try and make a DIY CV/Gate-sequencer for it?
So, there's a new project in the making! But, this is more than a possible future plan (like the Juno and JX-editors).

It'll be waaay simpler than the Matrix-1000 editor so it should be a lot quicker to build and program. Preliminary name: Mörckstep, in lack of better ideas...
I want to keep it simple, yet flexible, cheap and easy to use.

Here's what I've drawn on paper so far. Layout is not decided of course. This is mostly a rough sketch of what kind of buttons I want.

I will try to buy as few components as possible, partly because I have a tendency to buy things just because "they might come in handy", but mostly because I don't have a job anymore so I shouldn't be spending money :(

I have a few PIC microcontrollers at home which I, of course, bought because they might come in handy. So, I have decided to use one of them. The best candidate is the PIC16F685:

Program flash memory: 4k Word (7kB)
RAM: 256 bytes (wow)
EEPROM: 256 bytes
I/O pins: 18

The other PICs I have have less RAM (yes, it's possible)and fewer I/O pins.

As seen in the drawing above, I expect a 16-step pattern to totally occupy 34 bytes: 2 bytes per step (step, length, trig etc) and 2 bytes for pattern mode info (first and last step, pattern direction etc). So with 256 bytes of RAM I should be able to have something like 4-6 different patterns in RAM, depending on how much the program itself will need.

I am considering a pattern copy buffer (will of course occupy another 34 bytes of RAM) so you can duplicate patterns.
I am also considering trying to use the EEPROM as a non-volatile memory to store patterns. It would probably be VERY convenient to not have to reprogram your sequences each time you turn the power on...

Now I have to order a lot of buttons and stuff though :(
At least this is a smaller project than the Matrix-1000 editor, yet bigger than the Poly61 dataknob, so I might finish it relatively quickly :)

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