Re: TI-H: More AVR Qs

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Re: TI-H: More AVR Qs


You could always go out and buy a HOBO data logger by Onset, built for the
task.
www.onsetcomp.com

--nick


Nick Foster / Bistromath / zaphod@coe.neu.edu
KeyID 2048/1024 0x663CB446
6CAF FFD4 F9BA 64BA ECF9  032E 7402 3886 663C B446



----- Original Message -----
From: David Knaack <dknaack@rdtech.com>
To: <ti-hardware@lists.ticalc.org>
Sent: Monday, October 11, 1999 1:16 PM
Subject: Re: TI-H: More AVR Qs


>
> Greetings,
> This is a consolidation of several replies and my responses to my
questions
> about AVRs.  There are a couple more questions at the bottom.
>
> Thanks for your input everyone!
>
> Nick wrote:
> >[Timing precision and accuracy depend] on what you're using as a clock
> >source. if you're using a high-grade crystal with some bullet-proof
wiring,
> >the spec sheets for the part can be extremely accurate (i know that the
> >higher-end pics can meausre down to 10 nanoseconds or so..)
>
> For my data logging project I will be needing accuracy and not much
> precision. I'd like a drift of less than a second or two over a month.
I'll
> probably be running it at 4Mhz (or slower, power conservation is more
> important than speed).  The times I record only need to be precise to
about
> a second or so.
> Would the internal RC clock get me that kind of accuracy (withing a couple
> of seconds a month)?
>
> For my timing project I'll be measuring durations of around 25 seconds,
with
> precision of better than 1 millisecond.  I figure I'll run that one at 12
> Mhz. Does this sound like a reasonable goal?
>
> Grant wrote:
> >You should use the 8515 for digital logging and 8535 for analogue
logging.
> >They both have 512bytes of SRAM.
>
> 512 bytes is way small for my data logging application, which could
require
> up to 8Kb per sensor channel if left unattented for a month or so.
>
> The analog inputs would be nice (ie, cheaper), but for now I'm sticking
with
> digital sensors (I happen to have some on hand). I'm thinking the One
> Wire(tm) sensors from DalSemi would be nice, but they cost too damn much.
I
> like them cuz I can put several on the same bus, and they are reasonably
> small, so I can stick them at the end of probes and such.
>
> >Use a Mega103L if you need 4k.
>
> Cost and size are important factors here, I'm using the SOIC version of
the
> AT90S1200, the Mega versions are both too big and too expensive.
>
> >All memory bus AVRs can use an external 64kbyte of SRAM.
>
> What is a memory bus AVR?  Does that apply to the 1200?
>
> >EEPROM would die in a few hundred thousand accesses.
> PerErik wrote:
> >Thats true... better with a SRAM and a Battery.
>
> For my data logging application it would typicaly be cleared every month
or
> every week at the most, so that won't really be a problem.  The timer
> project won't need any memory for data storage (results will be sent
> directly to a computer via serial port).
>
>
> Grant wrote:
> >Your AT90S1200 has built in EEPROM.
>
> Unfortunately the 64 bytes of EEPROM on the 1200 is next to useless for my
> data logging.
>
>
> From: PerErik Klarenfjord <el8klap@cse.kau.se>
> > AT90S1200 do instructions very fast and have 32 registers... but i cant
> see any
> > "builtin" RAM. :-/
>
> The 1200's don't have any SRAM, the 2313 and 2323 have 128 bytes, the 4414
> has 256, the 4424, 8515 and 8535 have 512, the mega chips appear to have
4K.
> You can check the spec sheets at Atmel for specifics.
>
> > Do you know the price compared with 16F84 ?
>
> The commercial versions in 20 pin DIP from insight electronics are:
> AT90S1200   2.09
> AT90S2313   3.09
> AT90S2323   2.73
> AT90S4414   5.72
> AT90S4434   6.71
> AT90S8515   7.45
>
>
> Ok, now a couple more questions.
> For now am locked into the AT90S1200 (I already have them).
>
> Is it difficult to communicate with the computer via a serial cable?
Since
> my AVR will be using 5v, I presume I will need an RS232 level shifter
(I'll
> be communicating over fairly long distances).  Is there AVR code available
> somewhere that I can use for RS232 communication?
>
> Is code available to do a PWM output?
>
> Thanks,
> DK
>
>
>
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