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'[PIC]: Hardware Design Challenge'
2001\07\10@085006 by Russell McMahon

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Well, sort of
More a "which way should I jump" challenge.
Smallish run commercial project - say 100 to 200 units.
Cheaper would be nicer but labour costs will predominate.
Lower than higher current nice.

Processor sends serial to a printer, serial from a GPS, serial from a card
reader, reads/writes a 32K IIC eerom, talks to a central processor.
All inter peripheral links are N81 ASCII at true RS232 levels. All data
links are at 4800 baud.

Want to get this going with minimal effort and cost. At present Scenx with
virtual peripherals seems the probable easiest.

3 x 4800 UART receives
2 x UART TXs
1 x EEROM read/write
GPS data filtering
Data request/write control
Data direction to/from peripherals.

Send data to central processor via 4800 baud link.
Abort GPS read if card reader starts.
Can handle card reader and eerom write if both overlap.
Maybe queue card reader if occurs during eerom read but maybe abort block
read and repeat thereafter.
eerom read / write is always either 2 bytes or 64 bytes.

GPS should have output filtered to normally only forward RMC string (coz at
4800 baud this takes about 15% of channel bandwidth with 1 second update
whereas all standard messages take about 85%).

With virtual UARTS with say 4 samples per bit at 4800 baud that's 50 uS
polling cycle.
Scenix handles with ease.
20M PIC also really.
Just maybe a 4 M PIC (maybe).

Anything out there with 3 hardware UARTS and costs about nothing ?(I'm being
lazy)

Could just about do this with 8 i/o lines (2 x TX, 3 x RX, 2 x IIC = 7)
Something else will crop up needing at least one more.

Modest EEROM on chip would be nice but not essential.

Scenix is not cheap and is power thirsty but the virtual peripherals do look
attractive.

Any thoughts???


     Russell McMahon
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2001\07\10@091256 by Alan B. Pearce

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>Anything out there with 3 hardware UARTS and costs about nothing ?(I'm
being
>lazy)

>Could just about do this with 8 i/o lines (2 x TX, 3 x RX, 2 x IIC = 7)
>Something else will crop up needing at least one more.

>Modest EEROM on chip would be nice but not essential.

Use a maxim i2c UART chip on a low end PIC? using I2C would also allow IBC
EEPROM if needed.

You do not say what sort of card reader. If it is a swipe card then it could
beep for retry if something else is happening that fouls up the read.

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2001\07\10@120659 by Olin Lathrop

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> With virtual UARTS with say 4 samples per bit at 4800 baud that's 50 uS
> polling cycle.
> Scenix handles with ease.
> 20M PIC also really.
> Just maybe a 4 M PIC (maybe).

Not sure how relevant this is, but for what it's worth...

I had a situation similar to this where there was a lot of different I/O,
but none of it particularly fast or time critical.  It was also clear that
requirements over time would change.

We ended up giving each periperal its own dedicated little PIC, with all the
PICs and a central processor (another PIC) talking over an on-board IIC bus.
This had the added advantage that the specific driver details were in the
individual PICs.  The central processor would send a message, for example,
to print a line of text.  The printer controller PIC then dealt with the
details of how to make it happen on that particular printer.  This
modularity should make it easier to switch to a different manufacturer's
printer, GPS, etc.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olinspamKILLspamembedinc.com, http://www.embedinc.com

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2001\07\10@123811 by Douglas Butler

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       The multiple processor solution may well be the way to go.  Especially
when the projects specs are fuzzy, as it lets you design the parts that
are known while the marketing people dither about the rest.  Each little
part can be trouble shot separately and new features are easy to add.
       A few years ago I inherited a failing project with a 386 processor and
an FPGA handling ten timing signals.  I replaced it all with ten PICs
one for each channel, and one 68HC11 "Traffic Cop" to coordinate.  It
was up and running in no time.  Whenever one of the timing channels
changes, we just make up a new channel PIC.

Flexibility wins!

Sherpa Doug

> {Original Message removed}

2001\07\10@131944 by Terry

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Russ, check out the Cypress PSoC. I swore i'd never touch another M8 MCU
but this chip is lookin mighty tempting. 8 digital configurable blocks, 12
analog blocks, 1 MAC etc... All under US$3 (10K) for the 20 and 28 pin
versions.

Cheers
Terry

At 12:49 AM 7/11/01 +1200, you wrote:
{Quote hidden}

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2001\07\11@232825 by M. Adam Davis

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Circuit Cellar had a nice article on these, and I recently got to see
them at Chicago ESC (talk with the booth people, etc)

You should look into these, especially if you're thinking about using
more than one PIC.  It has 8 digital 'blocks' which can each be
configured individually as PWM, UART, Timer, etc.  It has twelve
similarily configurable analog blocks, and a Cypress cpu core.

They are trying to get digikey to sell them, but you can go through
other distributors.  A full ICE is $125, free software on the website.
The software does not have simulation capability yet, but they are
looking toward that end.  It's made by a subsidiary of Cypress, Cypress
MicroSystem, http://www.cypressmicro.com/ .

Another article is available online from Electronic design,
http://www.planetee.com/planetee/servlet/DisplayDocument?ArticleID=12992#Top


-Adam


Terry wrote:

{Quote hidden}

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2001\07\13@082502 by Kashif Ali

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part 1 497 bytes content-type:text/plain; charset=us-ascii (decoded 7bit)
Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit You ask for hardware challenge, thats why I am asking you a question I am facing a problem of external reset with 16f874, please give me the complete solution of reset (including configuration bit settings), I have a little experience of 16f84a, and have no problem of reset. I use this external reset for both uC but 874 did not response. [Image] Kashif Ali
part 2 8456 bytes content-type:multipart/related; boundary="------------2214477EF6C882B58E14ED12" (decode)

part 3 141 bytes
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2001\07\13@085957 by Jinx

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part 1 1284 bytes content-type:multipart/alternative; (decoded quoted-printable)


------ 2001\07\15@232817 by Alexandre Domingos F. Souza
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>Want to get this going with minimal effort and cost. At present Scenx with
>virtual peripherals seems the probable easiest.
>3 x 4800 UART receives
>2 x UART TXs
>1 x EEROM read/write
>GPS data filtering
>Data request/write control
>Data direction to/from peripherals.

       I'd use MCS51. With 4K of internal program memory and EASY OF PROGRAMMING, this is well suited to this task. I've done what you are doing before.


---8<---Corte aqui---8<----

Alexandre Souza
RemoveMEtaitoTakeThisOuTspamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2001\07\16@023309 by Kashif Ali

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Dear Jinx,

I still found no result, may be I'm ignoring something in configuration
bit, please tell what can I do ?

Kashif ali

Jinx wrote:

> The topic was discussed about a year ago, and this circuit was
> generallythought to be the one with optimum components for rise times
> and currentdraw

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2001\07\16@041220 by Jinx

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> I still found no result, may be I'm ignoring something in
> configuration bit, please tell what can I do ?
>
> Kashif ali

I'm not sure. My experience is only with F84 and F628 and I
assume the F877 MCLR is also purely hardware, and nothing
you could do in software would make any difference. The only
thing I could suggest is to physically check the components.
Perhaps the current limiting 100R is open or high Z or the
switch is faulty. Perhaps even a broken wire. Possibly a nasty
voltage has got into MCLR and destroyed a gate or two in the
Reset path before the actual uC part of the die

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