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Subject: Re: PIC and a Hi from Sweden :)
Name:
 Bob
Date: 1/27/2005 5:26:51 PM (GMT-7)
IP Address: 68.43.169.174
In Reply to: Re: PIC and a Hi from Sweden :) posted by
RoadRunner
Message:
Your a student you have no xtra money to spend.
I never got around to learning C but even if I did the native PIC language is both assembly & basic which is easy for me & gives me the chance to program in different ways to get a better outcome.
Rows & Collums is normally used for manual momentary push buttons switches like keypads for inputs.
And for outputs like driving 4 didgets LED number displays, powering each segment. Depending on the way they are wired & programmed the power drain can be small or huge. Add one input check for a button scan & your LED display can start to flicker bad. Yes this is what had happened to me & I did not have the time to fix it totally right either.
So how many of your inputs are manual buttons ?
If not buttons then 30 inputs + 10 outputs = 40 pins before TCP/IP & you have 33 or 34 I/O pins depending on which of the two PICs you mentioned.
This is a negative problem.
The row & collum trick is done by Outputting on either the row or collum side (one of its lines) & inputting on one of the collum or row lines.
Like you had 30 inputs say they are all buttons they could be covered with 5 rows & 6 collums.
You could then turn on row 1 as a high output (near 3 to 5 volts), then turn on collum 1 as a input & check to see if its high (button pushed) or low (no button). If no button then turn collum 1 back to neutral (not an input). Collum 2 would be turned to an input & you would read that one.
& so on to collum 6. After which you would turn off row 1 as an output & do row 2 as an output.
This is what you would really do after you have detected a button pushed to find out which one is down. To fast scan check for a button just make all outputs on & all inputs on & just keep reading for a high signal on any of the 6 lines or only 5 lines if you reverse my example. To make a an even faster check leave the rest of the port empty & low with a resistor so a port reading > 0 equals at least one button down. It is even alittle more complex then this as this is the short version LoL. Its only to help you stop & think as this can be fun stuff, email would be the best way after this.
My LED flashlight project I needed to keep the price down & I wanted to drive more then 11 leds (11 outputs under $2) thou only one at a time (your 33 I/O pins was not enuf & was to expensive over $7 per chip). I found an old CMOS IC around 36 cents each & has 1 of 10 outputs on at all times. With this one IC & one 11 I/O PIC I can drive 100 leds & only one LED on at a time. In truth thou the LEDs would be very dim & may require much more then 12 volts to get the proper 3.5 volts needed to drve the LEDs without burning them up.
Just some food for thought.
Bob
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