[sdiy] microcontroller selection!

[Neil Johnson]

Bret,

(caveat: its been a few years since I last looked at the OOPic modules)

Firstly, _any_ microcontroller system that samples inputs, does some
processing, and spits out an answer will introduce a delay.  But, as you
point out, if you use a fast processor running native code, you can get
this delay down to something tolerable (say, under 1ms).

The OOPic runs a small interpreter, with user instructions programmed into
an EEPROM.  The OOPin interpreter can process up to 2,000 instructions per
second, so even if the simplest case was "writeDAC = readADC" then you're
immediately looking at 1ms delay (not counting anything else the OOPic is
doing).

You would be much better programming BASIC for the Atmel AVRs.  The free
version is limited to 2k target code, but that should be enough for your
simple projects:

	http://www.dontronics.com/basc-avr.html

Or there is a free BASIC compiler and other interesting stuff here:

	http://www.invtech.com.au/html/abc_software.html

Also, although the OOPic blurb says its multitasking, objects, blaa blaa
blaa, in practice its code is all running in sequence in some fashion
(possibly round-robin).

> Even with an Amtel microcontroller, there's a chance that a/d conversion
> or sloppy programming could cause small timing issues.

True, but it depends what you consider "small enough".  For example, you
should be able to read an ADC, do some maths, and write the result to a
DAC in under 100us on a decently fast AVR.

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
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