Dual MAX7219 Chips and displays simultaneously?

ifright

I need to display the same information on two separate numeric displays. One is local, the other remote - about 50 feet away in another room. I have two MAX7219 driving 3 digits each. A Basic Stamp 1 is running the displays.

I have tried running the chips in parallel sharing the Data, Clock & Load lines - then both displays stop working.

Is there a way to split or duplicate the lines for each display? Is there a chip for that?

Do I need to somehow use another set of pins from the BS1 and duplicate the information (Data, Clock & Load lines) on those pins? Is it possible?

Gadgetman

If I remember correctly, it's possible to daistchain the 7219 chips...
(The output of one set is connected to the input of the next set)
Then you can just clock ot the samedata twice to mke it work.

Note: NEVER parallell couple DATA pins unless you're absolutely certain that only one is active at any time and that the others are in a 'high-impedance' mode. Otherwise you may end up short-circuiting them.

Zoot

You can share all the lines except the load/latch lines. Since the 7219 does not output data on it's data line (only accepts input) you can safely tie those together. The clock lines likewise. Each load/latch line would need it's own pin, so 4 pins would let you control both 7219s (1 shared data pin, 1 shared clock pin, 1 latch pin for the first 7219, 1 latch pin for the second 7219). To drive either one you would shift out as normal, then pulse whichever latch line is appropriate for the chip you're shifting to.

Daisy chaining would cut it down to 3 pins, and you would use the Q' (data out) pin of one 7219 to feed the Q (data in) pin of the second 7219. This makes sense if both chips are in close proximity and if you don't mind setting up your code to always load BOTH chips at once (the second chip in the chain receives the first set of bytes out, the first chip in the chain receives the second set of bytes out).

ifright

Thanks Gadgetman and Zoot!
I shall try your recommendations.

ifright

I managed to find a solution to my problem by using a 74LS244 octal buffer/line driver to 'split' the Data, Clock and Load lines to both displays. It provides fresh clean signals to both MAX7219 chips. I also found a diagram that showed 10K pull down resistors on the Data, Clock and Load lines at the chip which has helped significantly. I also added a .1uf cap at the chip for switching noise. The displays are part of my project on my other thread http://forums.parallax.com/showthread.php?133736-Orchestra-Pit-Depth-Display .