AW: PIC power?

Paul Maddox Paul.Maddox at unilever.com
Fri Nov 19 17:08:32 CET 1999


All,

  Without wishing to start a flame war, I beg to disagree with
you comment about the AVR being behind the i486, its a different
game.. the 486 is designed to try and do everything, the AVR is
aimed at ONE market, I wouldnt say its behind, just in a different
portion of the market.

  Ive started using the AVR for my projects (check out my
4 channel Midi>CV convertor on my webpage) it was pretty
is get going, it doesnt have bulky over heads that an intel 
does, like ram/rom/hdd/screen/keyboard/mouse/bus controller/etc/etc.
It takes virtually no power (5V at 3mA running at 8Mhz).

  Agreed its not 32 bit, but hang on, midi is only 7 bit (for most
stuff such as controllers and note).

  Ive decided to take up someones comment about a DDL
and Ive ordered some sample ADC/DAC (serial) from Analog
Devices and I reckon I could make a DDL with CV  control
of delay time without any hassle, I plan on using 16Bit serial
ADC/DAC's, these run at 2Msps, which is MORE than enough
for audio DDL, so 16 bit IS possible without any problem.

  For number crunching and 32bit power, yes the H8 is
better but I wouldnt go as far to say beat the AVR, again
its a different market..

  As you say the *BEST* thing about the AVR is its low cost
for its power..9UKP for a 8MIP micro with Uart/ram/eeprom/ISP.

  Personally I dont care for PIC's, Ive looked at them and there
is too much conflicting information, the Assembler looks like a
nightmare and doesnt run at 1 instruction per clock cycle. They
dont seem flexible enough, maybe this is why there are so many
varients out there (you seen the latest farnell catalog of pic parts,
hundreds).

  Ok, I know this is only partly relivant to synthdiy, but I think
micros should be classified as part of synth diy, they're used
in Midi>cv convertors and drum machines and much much
more (I know a man who's written a midimerge just using an
AVR and 3 opto isolators). so please dont flame me for an 
off-topic posting..

  Mikko, sorry if this sounds like a dig at you, its not. I just happen
to feel very passionate about the AVR range and theres not enough
sites out there that a relivant to AVR's and Music (Ive only ever
found 2, and now mines there so that makes 3).

  Paul

*********************************************************
*   Modulus Synthesiser DIY page ;-				*
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*	  Paul.Maddox at unilever.com				*
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-----Original Message-----
From:	Mikko Helin [SMTP:helin at uta.fi]
Sent:	Friday, November 19, 1999 11:18 AM
To:	Dr._Jörg_Schmitz
Cc:	synth-diy at mailhost.bpa.nl
Subject:	Re: AW: PIC power?

On Fri, 19 Nov 1999, Dr. Jörg Schmitz wrote:

> > > Are any PIC's powerful enough to do DSP based stuff?
> > > 
> > No they aren't.
> 
> I think it depends on : I plan to use PICs for control voltage generators,
> like complex envelope generators and LFOs and so on. 
> So this isn't exactly DSP (dig. sig. processing) but more DSG (dig. sig.
> generation).
> 
> For 16 bit audio signal processing (48KHz, for example) a PIC is too slow. 

I've been also planning some kind of MIDI controllable CV generator,
and I've been comparing PIC with Atmel's AVR stuff, which is much
more suitable mc for the task. OK, there are PIC's with hardware
multiply operations, and soon there's also similar AVR (atMega161).
With PIC's you can't easily handle 16-bit words like on AVR, which
can sum to 16-bit words with just 2 instructions, like

 ADD r2, r6
 ADC r3, r7

Also 16-bit move is just one instruction in one cycle on AVR. 
You'll need a lot of that kind of handling with LFO's and EG's, as 8 bit
LFO or EG is substandard.

Anyway, even the AVR is still way behind Intel 486's, where
you can do all arithmetics in 32 bits, and easily simulate
analog VCO's, VCF's and VCA's. Obviously they are not ideal
solution (obsolete soon, need hefty and noisy PSU, keyboard,
display etc.). Best would be some 32-bit RISC mc like
Atmel's or other manufacturer's ARM core processors,
Hitachi H8/300 series, even 80C186 stuff could beat AVR's,
but none of these have the low cost developement tools
for hobby users.

However, PIC's are great for minimal tasks like reading
pot's sending MIDI out (even without ADC's), converting
between MIDI sync and say DIN sync with drum machines,
scanning keyboard etc. 8-bit delay is ok, as well as
16-bit as long as you have parallel input/output
converters available, and generally as long as you
don't need multiply instructions or arithmetic
shift operations are sufficient. Anyway, if the PIC
does the thing you need then use it, but be prepared
to use some other MC when täs not enough.

-Mikko

> 
> J.S.
> > 
> > > Like say an 8-bit delay?
> > > 
> > Yes, that's possible. Use 16F877 and 64kbyte SRAM and
> > some 8 bit DAC (PIC16F877 already has 10 bit ADC).
> > At 32 kHz sample rate you should be 2 seconds delay.
> > 
> > -Mikko
> > 
> > 
> > > ~bud
> > > 
> > > 
> ________________________________________
> Dr. J. Schmitz
> http://www.patho.bonn.com
> http://members.xoom.com/jmschmitz
> ----------------------------------------
> 





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