LED Message Board!!!

[c3cube]

I'm doing a project on LED message board. It's only part of my project title. My title required me to write a PC simulation program on LED message board with 3 effects and 3 size selctions. The second part is the LED message board itself, then the third part is the wireless upload from the PC to the LED message board.

I've almost done my first and third parts of my title request, but when it comes to the LED message board, my brain's becoming blank!!! I got a circuit diagram from http://www.geocities.com/neomatrix80/Embeded/prjschem.jpg, but I have no clue how it runs as a whole? I basically know how the shift register work but when it's connected to the microcontroller, all starts confusing. Yet, I'm not that good in assemble programming, thinking of using C or mikroBasic but still, I'm not sure how the port pins should run???

I still have a month before the due date of my project, so PLEASE HELP me!!! All I need is an clear idea on how to light up a character "R" or others on this circuit. So can anyone look at the circuit and provide me some simple algorithm or program that works on this circuit.

 

[Pommie]

The circuit diagram is a little hard to see but I think I've managed to follow what is connected to what.


To light any LEDs then 32 bits of data have to be written out of Port A bit 1.

To write a bit of data you do:-
Place data on RA1
Make RA3 high = 1
Make RA3 low = 0

The data you send will represent 1 row of LEDs.

As I’m a dinosaur, I count from zero upwards. Therefore the first bit is bit zero and the last bit is bit 31.

The first bit (bit 0) should be zero if the LED in the right most column is to be lit.
Bits 1 to 23 are the same for the other columns.

Bits 24 to 31 represent the row that is to be lit. Only 1 of these bits should be set to 1.
If bit 24 is 1 and 25 to 31 are zero then the top row will be lit.

After the 32 bits of data have been sent to the shift registers, you need to tell the shift registers to display what you have sent. You do this by strobing RA2.
You do this by
Making RA2 high
Making RA2 low

So, to light up the whole display you would do the following.
Send the data that represents the top row as the first 24 bits.
Send 1000000 as the next 7 bits.
Strobe RA2
Delay a short time.
Send the data that represents the second row as the first 24 bits.
Send 0100000 as the next 7 bits.
Strobe RA2
Delay a short time.
.
. do rows 3,4,5&6
.
Send the data that represents the seventh row as the first 24 bits.
Send 0000001 as the next 7 bits.
Strobe RA2
Delay a short time.


Repeat the above.

HTH

Mike.

 

[Pommie]

I should mention that the circuit that you linked to is not ideal for the algorithm that I outlined above. A better algorithm would write the column data to bits 24 to 31 and only set 1 bit low of bits 0 to 23. This of course would need repeating for each column and so would have a lower refresh rate. It would however reduce the current required per output and so would be desirable. An alternative is to put a transistor on each row output to increase the current capability.

Mike.