[sdiy] microcontroller selection!

Bret Truchan clone45 at hotmail.com
Fri Aug 8 22:59:46 CEST 2003

Hello everyone!

[ This question is unrelated to my question on the sampler module.  ]

I just completed a prototype of a Doepfer compatible module that uses the 
OOPic microcontroller.  The module is a generic - programmable module for 
logic function.  It can do sequencing, clock division, pattern generation, 
etc.  I'm working on a website that shows it off, so I'll have a demo soon.  
I'd love to sell it soon and share the joy! ( I may start my own business 
making music gear!!  Woop! )

In any case, now that it's finished, I've found that there are some speed 
issues.  Especially when doing a/d conversion.  The module is quite 
functional and fun, but there's a small delay between the time that you 
clock it to when it produces output.  BEST case (very rare), is a nearly 
instantaneous response... but that's the simplest function programmed in the 
fastest way possible (using virtual circuits in the oopic).

More realistic programming introduces delays ranging from 1/100th of a 
second to probably much much worse.  Part of the timing issues are 
introduced when I do slow a/d conversion.  Some timing issues exist because 
the OOPIc is very slow when programmed in a traditional fashion.  My module 
has a serial port right on it, so users can program in their own stuff, and 
they'll probably opt for the slow, easy method of programming.

Even _with_ the input to output lag, the project has been a raging success.  
It's a very, very cool module.  It's internally consistent, so using it as a 
4 part pattern generator works great.  The reason I choose the oopic is 
because it's very easy to program and hooks up via a serial port.  The 
software to program it is free and very easy to use.

Here's my question - - - should I go with this solution, using the slow-ish 
OOPic, or is it worth researching using a faster microcontroller?  The basic 
stamps might work better, but wouldn't I still get delays when doing a/d 
conversion?  Another way to look at it is... if the module is going to be 
based on a programmable microcontroller, should it be *expected* to have 
clock->output delays some of the time?  (dependant on the programming 
efficiency, etc).  Obviously I'd have to make that very clear if I sold it.

I would prefer a much faster family of Amtel microcontroller, but I really 
wanted to make this super easy to program, and super easy to hook up to a 
computer.  Even with an Amtel microcontroller, there's a chance that a/d 
conversion or sloppy programming could cause small timing issues.

Thanks for your input!!
- Bret

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