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'[PIC]: Simplest, cheapest,'
2002\03\28@104351 by Drew Vassallo

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I want to display just 2 numbers out of the PIC somehow.  Doesn't matter
how, just the simplest, easiest, cheapest solution.  Could be an LED
display, LCD, smoke signals, it doesn't matter.

I'd like to use a 12C67x series 8-pin PIC, though, so I only have 3 lines to
use maximum.  If it's not possible in this case, I would have to move to a
larger chip, but it's not preferred to do this.

I have a 2-wire LCD interface already working, but I'd like to make it
simpler/cheaper if possible.

Any suggestions?

--Andrew

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2002\03\28@105117 by Michael Rigby-Jones

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{Quote hidden}

What range are the numbers you need to display? A couple of shift registers
and a handfull of LED's could be used to read up to FFh as long as you are
prepared to read in binary, and would be hard to beat for price.

Mike

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2002\03\28@111428 by Alan B. Pearce

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> I have a 2-wire LCD interface already working, but I'd like to make it
> simpler/cheaper if possible.

The only way to use less pins is to do some form of 1-wire interface to
another device. Otherwise two wires (clock/data) is about as simple as you
are going to get.

For simplest a shift register with a number of discrete led's is about as
simple as it will ever be, unless you can use a 16F628 as a one wire
receiver, perhaps using MCLR as the input pin to maximise the number of led
driving pins available.

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2002\03\28@111433 by Byron A Jeff

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On Thu, Mar 28, 2002 at 10:43:51AM -0500, Drew Vassallo wrote:
> I want to display just 2 numbers out of the PIC somehow.  Doesn't matter
> how, just the simplest, easiest, cheapest solution.  Could be an LED
> display, LCD, smoke signals, it doesn't matter.
>
> I'd like to use a 12C67x series 8-pin PIC, though, so I only have 3 lines to
> use maximum.  If it's not possible in this case, I would have to move to a
> larger chip, but it's not preferred to do this.
>
> I have a 2-wire LCD interface already working, but I'd like to make it
> simpler/cheaper if possible.

Drew,

Even the one solution I can proffer is going to cost you a chip. BGMicro
surpluses some HP 4 character 5x7 modules with a serial interface. $1.19
each or 10 for $0.89 per. It has a funky shift register interface that shifts
in all 28 bits for the same column in each of the 4 displays. You then choose
which of the 5 columns to light. There's the problem because it's a parallel
interface and would require it's own shift register to stay within the pin
constraints given. The catalog page can be found here:

http://www.bgmicro.com/pdf/page8.pdf

Good luck in your search.

BAJ

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2002\03\28@113531 by Dave Mumert

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Hi Andrew

Do you know Morris code? That would only take 1 output.

There is a 16 channel serial input LED display driver available from Allegro
http://www.allegromicro.com/sf/6276/
It is under $3.00US.

Dave

> I want to display just 2 numbers out of the PIC somehow.  Doesn't matter
> how, just the simplest, easiest, cheapest solution.  Could be an LED
> display, LCD, smoke signals, it doesn't matter.
>

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2002\03\28@124152 by Drew Vassallo

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BGMicro
>surpluses some HP 4 character 5x7 modules with a serial interface. $1.19
>each or 10 for $0.89 per. It has a funky shift register interface that
>shifts
>in all 28 bits for the same column in each of the 4 displays. You then
>choose
>which of the 5 columns to light. There's the problem because it's a
>parallel
>interface and would require it's own shift register to stay within the pin
>constraints given. The catalog page can be found here:

This is EXACTLY what I want.  I'm not an EE, but I assume the shift register
is relatively easy to use?  I've never actually used them.  Operating speed
is not a concern in this application.  I wouldn't need to do anything other
than display the numbers until they're finished being displayed.

Could you give me some advice on how I'd use the shift register as an
interface?

--Andrew

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2002\03\28@125357 by Byron A Jeff

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On Thu, Mar 28, 2002 at 09:33:48AM -0700, Dave Mumert wrote:
> Hi Andrew
>
> Do you know Morris code? That would only take 1 output.
>
> There is a 16 channel serial input LED display driver available from Allegro
> http://www.allegromicro.com/sf/6276/
> It is under $3.00US.

I think we need to go back and ask for specification clarification. What's
the most important criteria, cost or board space? Once you're talking about
$3.00 solutions then what's the benefit over using a larger PIC?

I'll start the discussion. Let's start with the 25 part price at Digikey for
the 12C508 and the 16F627. $1.72 for the former and $2.01 for the latter.
29 cents difference. board real estate wise the 16F627 adds 10 pins, all
of which can be used for I/O. We know that with 8 pins and 2 nickel transistors
we can drive two 7 segment displays directly from the PIC. In fact we can
ditch the external transistors if we assign one more I/O pin to the task.

BTW if it's directly connected to the PIC with no external drivers, the
software must multiples each segment of the display, not entire displays so
that the PIC's port won't be overloaded.

Now with that in mind let's redefine: Is there a serial I/O solution that
takes less than 10 pins of board real estate and cost less than 30 cents?

I can't think of one. Even my previous solution would have required a 14 pin
driver in addition to the display itself.

So here's my bar. The simplest, easiest, cheapest solution is a 16F627
directly driving a 2 digitd LED display using 9 I/O pins. It cost 29 cents
and 10 I/O pins.

Any takers?

BTW I picked the 25 part price for two reasons. 1st if digikey's minimum order
and secondly the 25 part price ditches most of the overhead for single pieces
and gives a truer sense of the actual cost of the part. The difference in
single part prices is $1.45 BTW.

BAJ

{Quote hidden}

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2002\03\28@130912 by Byron A Jeff

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On Thu, Mar 28, 2002 at 12:41:52PM -0500, Drew Vassallo wrote:
> BGMicro
> >surpluses some HP 4 character 5x7 modules with a serial interface. $1.19
> >each or 10 for $0.89 per. It has a funky shift register interface that
> >shifts
> >in all 28 bits for the same column in each of the 4 displays. You then
> >choose
> >which of the 5 columns to light. There's the problem because it's a
> >parallel
> >interface and would require it's own shift register to stay within the pin
> >constraints given. The catalog page can be found here:
>
> This is EXACTLY what I want.  I'm not an EE, but I assume the shift register
> is relatively easy to use?  I've never actually used them.  Operating speed
> is not a concern in this application.  I wouldn't need to do anything other
> than display the numbers until they're finished being displayed.

It's easy once you understand the format. Let me show you with 3 displays that
are 2x2:

A1 C3 E5
B2 D4 F6

Where the letters are in column 1 of the display and the numbers are column 2

The shift register shifts down the columns. So if you shifted the F6 bit
is ejected and replaced by the previous E5. Everything else shifts down/over
(i.e. D4->E5, C3->D4) and the new data is shifted into A1. Note that all of
the column bits have the same value. So 'C' in column 1 and '3' in column 2
are the same bit.

>
> Could you give me some advice on how I'd use the shift register as an
> interface?

Well you still need to deal with the issue of driving the columns. There are
5 column drivers, one for each column. So the process is

* Shift in the data for column 1
* Select the column 1 driver which lights column 1 for all 4 displays
* Shift in the data for column 2
* Select the column 2 driver which lights column 2 for all 4 displays

etc.

Now this is how I'd do it. The display has both a data in, shich gets shifted
into A1 and data out which has the current value of F6. So you can add a second
shift register to the chain to drive the columns. This only requires two I/O
so the thrid I/O can be used to select/deselect the column driver. Something
like a 74HC595 which has an output enable input. So you can then shift in 33
bits, 28 for the display and 5 for the 74HC595 column driver, then turn the
display on using the last I/O.

I still not sure think that it's as cost effective as driving a 7 segment LED
from a 16F627, but I do think that it's workable.

I have the displays if you need a sample or two. Drop me a line.

BAJ

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2002\03\28@155605 by M. Adam Davis

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The cheapest visual solution is one very cheap LED.  Like the old engine
indicators:

Blink the number of times for the first digit (1/4 second on, 3/4 second
off)
Pause for 2 seconds
Blink the number of times for the second digit (1/4 second on, 3/4
second off)
Pause for 5 seconds

Takes 25 seconds max to read the two digits off the display, but costs
less than a few cents, and only needs one line.

I bet there's even a way to do it with zero dedicated lines.

-Adam

Drew Vassallo wrote:

{Quote hidden}

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2002\03\28@170412 by Barry Gershenfeld

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>I bet there's even a way to do it with zero dedicated lines.
>
>-Adam

If you have a radio nearby, there is :)

Barry

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2002\03\28@185323 by michael brown

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Dave said
> Do you know Morris code? That would only take 1 output.

I bet this is the most inexpensive way and simple too.  Just drive an LED or
buzzer using Morse code.  Good idea.  Numbers are easy to learn.   ;-)

michael brown (N5QMG)

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2002\03\28@220746 by Thomas McGahee

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Instead of morse code, use a simpler code where ones are a short beep and
a longer beep is a five. Two longs means zero.

0 = beeeeep beeeeep
1 = beep
2 = beep beep
3 = beep beep beep
4 = beep beep beep beep
5 = beeeeep
6 = beeeeep beep
7 = beeeeep beep beep
8 = beeeeep beep beep beep
9 = beeeeep beep beep beep beep

Fr. Tom McGahee


{Original Message removed}

2002\03\29@014655 by Graeme Zimmer

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> Instead of morse code, use a simpler code where ones are a short beep
>  and a longer beep is a five. Two longs means zero.

No.   Is better to use the correct abbreviated morse characters...

1 7-
2 77-
3 7--
4 777-
5 777
6 -777
7 --7
8 -77
9 -7
0 -

................ Zim ........... VK3GJZ

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2002\03\29@023044 by Graeme Zimmer

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> No.   Is better to use the correct abbreviated morse characters...
>
>  1 7-
>  2 77-
>  3 7--
>  4 777-
>  5 777
>  6 -777
>  7 --7
>  8 -77
>  9 -7
>  0 -

Whups, where the hell did those sevens come from ???
trying again...

1  7_
2  77_
3  7__
4  777_
5  777
6  _777
7  __7
8  _77
9  _7
0  _

................... Zim

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2002\03\29@023450 by Graeme Zimmer

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>  1  7_
>  2  77_
>  3  7__

I give up

anyway goto   http://www.ac6v.com/morseaids.htm#AB

.............. Zim

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2002\03\29@044437 by Russell McMahon

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Lets see if the "7" monster cattacvks me too -


>  1  7_        o - - - -
>  2  77_      o o ---
>  3  7__      o o o - -
>  4  777_    o o o o -
>  5  777       o o o o o
>  6  _777    - o o o o
>  7  __7     - - o o o
>  8  _77    - - - o o
>  9  _7     - - - - 0
>  0  _       - - - - -



       RM

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2002\03\29@071758 by Diego Sierra

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Zim,

> >  9 -7
> >  0 -
>
> Whups, where the hell did those sevens come from ???  trying again...

You are using Outlook Express, same as me, there is something somewhere
that changes the coding. It happens to me either when I write a pound
sign and it sends a #.

Cheers,
Diego.

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2002\03\29@105543 by Bob Barr

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On Fri, 29 Mar 2002 12:15:36 -0000, Diego Sierra wrote:

>Zim,
>
>> >  9 -7
>> >  0 -
>>
>> Whups, where the hell did those sevens come from ???  trying again...
>
>You are using Outlook Express, same as me, there is something somewhere
>that changes the coding. It happens to me either when I write a pound
>sign and it sends a #.
>

That last sentence is liable to be a puzzler for some folks.
My thought is that you're referring to writing the symbol for pound
sterling.

The '#' character (I believe its proper name is 'octothorpe') is
commonly referred to as a 'pound sign' here in the US. At least,
commonly enough for Micro$oft's purposes. :=)


Regards, Bob

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2002\03\29@113907 by Diego Sierra

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>The '#' character (I believe its proper name is 'octothorpe') is
>commonly referred to as a 'pound sign' here in the US.

Oops, sorry, I do not know that. Yes, I was referring to the sterling
pound symbol.

And yes, your believing is true:

http://www.sigtel.com/tel_tech_octothorpe.html
http://www.quinion.com/words/weirdwords/ww-oct1.htm

>At least, commonly enough for Micro$oft's purposes. :=)

:D

Cheers,
Diego.

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2002\03\29@165209 by Barry Gershenfeld

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>http://www.sigtel.com/tel_tech_octothorpe.html
>http://www.quinion.com/words/weirdwords/ww-oct1.htm

Spotted something there that gave me the idea to tell the folks
here that what we are talking about looks like a tic-tac-toe board.

I have seen in the past some international keyboards where
the  "pound" symbol could be changed to the "pound" symbol.
That being the octothorpe in the US but changing to
the "pound-sterling" (looks like an L) for Britain. But
both above the "3".

As for Fr. Tom's suggestion, since nobody took the trouble to
do the obvious, ...

{Quote hidden}

Now, doesn't that clear everything up? ;-)

Barry

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