[ardour-users] MMC commands and remote control

[Geoffrey Wossum]

On Thu, 2005-03-10 at 19:11 +0000, Rob Fell wrote:
> > For me it's the other way round. I have worked with Atmels micros for a year
> > now and they seems to be very handy. I've heard that PICs are much more
> > complicated to program but this surely is subjective.
> 
> What does the programming hardware cost?  A PIC programmer only costs a 
> few UKP if you build it yourself.

I've had multiple years of experience with both PIC (16 series) and
ATmel AVR ATmega series microcontrollers.  For me, the AVR blows the 16
series away.  I've had a small amount of experience with 18 series PIC,
but I still like the AVR better.  And I'm not just saying that because
I'm working on an AVR right now.  ^_^ 

> If this project takes off, it'd be nice to sort out a complete free 
> toolchain and PCB artwork - just to make it easy for anyone who wants to 
> make their own :)

There is a complete GCC based toolchain for the AVR.  Check out
http://www.nongnu.org/avr-libc/

For cheap AVR programmers, check out http://www.sparkfun.com

I personally use STK200 or STK500 programmers for the ATmel parts, but
that's because my employer buys them for me.  These are going to run you
$50 - $100.  It's easy and cheap to build an STK200 knock-off though, as
all it is a DB-25 with a 74 series latch and a diode.  There's
schematics on the Internet for it, sorry I don't have a quick link to
it.

> > I know that, I have worked already with PCF8574 chips coupled over I2C bus to
> > increase the number of in-/outputs.

I use PCA9555 chips quite a bit as I2C I/O expanders.  They're nice to
work with.  16 programmable input/output lines with an attention signal.
Not sure of the cost, as BOM's aren't my concern.  

> >>A better option is to use rotary digital encoders - but they are
> >>difficult to use when you have many of them (the required sampling rates
> >>are surprisingly high to cope with high angular rotational rates).
> > 
> > I have used one half a year ago and I was not very satisfied with my results.
> 
> I've had good results in commercial products, but that was for only a 
> few encoders.  In automotive environments I needed 100Hz sampling and 
> some serious software filtering :)

The larger parts (ATmega128) have 8 A/D converters.  I would imagine
that the AVR also has enough horsepower to handle multiple encoders,
plus the MIDI stream, based on my experience with AVR's.  I use them
frequently for RF demodulation.  They have plenty of horse power for the
high sample rates and filtering required for RF demodulation, and still
have plenty have horsepower leftover for other tasks.  I also have an
802.15.4 stack running on some of my products, which does a LOT of work
on a 320 uS timer interrupt.

---
Geoffrey