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Pic help

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2005-2006 » Archive through 19 September, 2005 » Pic help « Previous Next »

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Koool
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Username: Koool

Post Number: 3
Registered: 08-2005

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Posted on Saturday, 27 August, 2005 - 09:06 pm:   Edit Post Delete Post Print Post

hello to all,
i want to design a moving message led display sign board using pic 16f84a i want to design of 8 * 32 of size.. 8 rows and 32 colums.. please some body help me how to design the hardware for 32 columns.. bcz pic have 8 lines for portb and 5 lines on porta .. i deceded to use 8 lines for row.. but i dont have idea how about colums.. pls help me.. and also help me is pic16f84a is capable for deriving such kind of led display.. and multifunction moving messeges..i want to scrool moving letters messege.. of long time.. please help me.. i will be so thankful ...
thanks a lot..
Khan.
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Admin
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Post Number: 28
Registered: 04-2005


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Posted on Saturday, 27 August, 2005 - 10:04 pm:   Edit Post Delete Post Print Post

When posting a new message, please be sure to use the Start New Thread link at the BOTTOM of the main EPE Chat Zone page, not the Start New Thread link within an existing thread.

Otherwise you will simply create a sub-topic off an existing thread, and no-one is likely to see your new message.

Thanks,

(Message edited by admin on 28 August, 2005)
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Paul_goodson
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Post Number: 75
Registered: 05-2005


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Posted on Saturday, 27 August, 2005 - 11:06 pm:   Edit Post Delete Post Print Post

you could give this a look
http://www.attiny.com/dotmatrix.htm
hope it helps
Paul
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Ashfaq
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Posted on Saturday, 10 September, 2005 - 01:31 am:   Edit Post Delete Post Print Post

I WANT TO MEASURE VOTAGES & CURRENT AND TAMPERATURE OF A POWER SUPPLY.I M USING ADC 0808 FOR THIS PURPOSE.I ALSO WANT TO SHOW SHORT CIRCUIT INDICATION.PLZ GUIDE ME.}
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Yesiam
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Post Number: 11
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Posted on Saturday, 10 September, 2005 - 03:13 am:   Edit Post Delete Post Print Post

The easiest way with the 16F84 is to use a single port for your 8-bit output for your rows and the 74HC595 serial to parallel shift register to operate your columns. The shift register will require 3 pins output on another port. It has an 8-bit parallel output and can be cascaded. For 32 columns you would need to cascade 4- 74HC595's.
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Eagre
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Post Number: 28
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Posted on Saturday, 10 September, 2005 - 03:39 am:   Edit Post Delete Post Print Post

I only must wonder why anyone is using the 16F84(A) PIC at tis time. It is obsolete and much more expensive than far more capable 18p replacements, such as the 16F88. I suppose if you have several in your "junk box" that is a reason. Otherwise, invest a little reading of spec sheets, and move ahead.

Ed Grens
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Paul_goodson
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Post Number: 80
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Posted on Saturday, 10 September, 2005 - 03:04 pm:   Edit Post Delete Post Print Post

Sorry but are we still talking on the same subject
"Moving message led display signboard"
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Microguy
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Username: Microguy

Post Number: 6
Registered: 09-2005

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Posted on Saturday, 10 September, 2005 - 10:25 pm:   Edit Post Delete Post Print Post

What was that the admin said about off topic subjects........


Koool, you need to "decode" the other lines. you can use 8 row drivers as the are.

But you will need to decode the column drivers. Using a 1 of 32 decoder, and the input would simply be a 5 bit binary counter (implemented in the PIC code)

Basically,

Set your column counter to Zero,
send out your row data,
turn off the row data,
increment the column counter,
send out the next row data,
turn off the row display,
increment the column counter....
repeat until you reach 31 and loop.

(or something similar, there are slightly other ways that involve slightly differeent timing, but the general idea is the same)
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Yesiam
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Post Number: 14
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Posted on Sunday, 11 September, 2005 - 12:07 am:   Edit Post Delete Post Print Post

Microguy wrote: "But you will need to decode the column drivers. Using a 1 of 32 decoder, and the input would simply be a 5 bit binary counter (implemented in the PIC code)"

Is there such an animal? I found a serial to 32 output driver chip by Allegro: http://www.allegromicro.com/sf/6818/. I'm not aware of a 5-to-32 addressable device. There is a 3-to-8 IC. It's a 3 line addressable IC which would still require 4 IC's for the column enables, and lest we forget 4 lines for the chip enables (unless you add another decoder for these), but would require less MPU clock cycles for output.
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Microguy
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Post Number: 10
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Posted on Sunday, 11 September, 2005 - 02:20 am:   Edit Post Delete Post Print Post

I don't know of a "1 of 32" decoder right off, but you can split it up.

Like two "1 of 16" or four "1 of 8" decoder chips.

Let's see if I can say this is such a way that it makes sense.

If you use two "1 of 16" (74XX154) chips, it's easier. 4 lines to decode, and one line to select which decoder chip to use. Easy. But there's a trade off, the chips are bigger and more expensive (not much though).

If you use 4 "1 of 8" (74XX138) decoders, there's a little more wiring to do, but the chips are easier to find and use.

This is generally something only you decide what to use.

Based on your expierence and the project size, how much wiring you want to do, parts availability etc...

I would go with one or two chips per display, with that type of design. But other people may go a different route, like one chip per display (so you can make a package type deal, end stackable).


It's all a matter of choice.


Go to http://www.fairchildsemi.com/ or some other place like that and brose their catalog. (or maybe browse the sellers like Digi-Key or Newwark because they'll tell you what they have on hand also) and look at the chip descriptions for things like "3 to 8" line decoder or "4 to 16" or "1 of 16"


Just have to do some research, and decide what looks best to you, based on your input, things like price and availability and your abilities.

(the manufacturers also have LOT'S of notes of how to use them, an incredible source of education, I used to read their data books like people read novel's, tons and tons of information)
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Magnum4
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Username: Magnum4

Post Number: 103
Registered: 04-2005


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Posted on Wednesday, 14 September, 2005 - 11:17 pm:   Edit Post Delete Post Print Post

This any help?
http://www.interq.or.jp/japan/se-inoue/e_pic6.htm
Regards,
Jim

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