Need help on countdown timers using 2 bicolor dot matrix without shift register.

Hey guys, I'm new to arduino. Just recently I just received an assignment, as what the title said, it's an 8x8 Bi-Colored dot matrix, meaning 24-pins. Any form of help will be appreciated.

EDIT: I'm using Arduino UNO & ORM-1588ASRG Dot Matrix.

What exactly does “without shift register” mean?
Is this a common cathode bicolor matrix, or common anode bicolor matrix?

I mean without the use of shift registers.
It's a common anode matrix.

Crossroads,
Couldn't he modify this example ? (I don't see the 74HC595 library in the code and it says "direct drive ")
http://playground.arduino.cc/Main/DirectDriveLEDMatrix#.Uyu08PldW_g

Needs 24 IO pins - either 1284P, 2560, or some external buffers to alternate 8 pins between the cathodes.

Oh, right. (DUH !) I guess he needs and I/O expander.

Sorry, but i didn't understand a thing y'all are talking about... mind filling me in?

Also, is therr any tuts i can follow?

raschemmel:
Oh, right. (DUH !) I guess he needs and I/O expander.

Yes, but I/O expanders are normally I2C. Which is a serial bus. So would that break the "no shift registers" rule? We don't know. You could argue an I2C i/o expander is a form of shift register. Same for max7219.

How about a couple of 3 to 8 line decoders, plus a couple of ULN2803s, 1:16 multiplex ratio. Only 12 lines needed.

Or a couple of octal counters (4012?) plus the 2803s. Only 10 lines.

AmosL, sorry, once we have had a quick techy discussion, will be glad to explain in more detail.

Paul

It doesn’t need to be that complex - drive the anodes, and buffer 2 sets of cathode drivers - then multiplex like you would a normal 8x8 matrix - 1 anode high at a time, 1 cathode low at a time.

If ULN2803 was put after the 'F244, then whole columns could be turned on, for more efficient multiplexing - 1 of 16 columns, vs 1 of 128 LEDs.

CrossRoads:
It doesn't need to be that complex

Well, your second diagram has 4 external ICs and uses 18(?) Arduino outputs. My suggestion has 3 ICs (4514 + 2 x ULN2803) and 12 outputs:

8 anode drivers
4 column address outputs

AmosL, we had better just check - this rule about "no shift registers" - are any other types of chips banned?

No. There is not. However, if it is easier to do this using Shift registers, do let me know. I can make arrangements.

AmosL:
No. There is not. However, if it is easier to do this using Shift registers, do let me know. I can make arrangements.

Yes, its easier using shift registers. Use 2 x tipc6b595. Total of 11 Arduino outputs required.

Okay, is there a schematic i can follow on that?

AmosL:
Okay, is there a schematic i can follow on that?

Maybe Bob will oblige. He seems to be in a particularly generous & helpful mood today...

Pardon my ignorance, but who's Bob?
Thanks in advance.

AmosL:
Pardon my ignorance, but who's Bob?
Thanks in advance.

Sorry. Bob is Crossroads, the guy who has been helping you and has already drawn up two schematics, just for you personally.

However, your insistance on not using shift registers, him putting in the effort of suggesting alternatives and illustrating them, followed by your sudden about-face may have left Bob feeling a little frustrated (I did).

Oh, I'm sorry guys. I... will just try to make do with what's taught in this thread. Sorry to bother.

Nope, just out of town for a funeral.
Think I’d go cd74ac164 for anodes, and tcip6b595 for cathodes. 3 pins. 3 spi.transfer’s to send out data.

AmosL:
Oh, I'm sorry guys. I... will just try to make do with what's taught in this thread. Sorry to bother.

That's ok. So... we have solutions without shift registers using 3 or 4 ICs and anything from 12 to 18 Arduino ouputs. Or with shift registers using 2 or 3 ICs and 3 to 11 outputs. You need to consider what else the project needs and how many Arduino pins you can afford to run the display. Let us know and I'm sure one of us can knock up a schematic gor you.

Paul