Driving MAX6951 & eight 7-segment displays

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,
I have Duemilanove & Arduino-0019 (upped from -0018).

I'm working on a project to to drive eight 7 segment displays for a fencing scoring machine, 4 will show the time remaining and 2 each will show the left fencers score and the right fencers score.
So far, prototyped code/hardware to write 6 bits to sit at inputs of a bank of 74LS374 registers (with 7447s to drive the displays), then creating a clock to each one by writing 4 more bits to the input of a 74HC154 and toggling a pin to make clock for a 374. Got that to work. Just have one 374/7447 wired up for now, but can move the clock line down the 154's output to show at least 5 would work (all I have coded up so far). Wiring that up 7 mores times would work, but would be a lot of ICs.

Found the Max6951, just need 9 wires out to each display, I think I could breadboard that and keep it working. Running 9 wires to each digit wouldn't be bad. Each digit is also hand build with 3 LEDs per segment - originally had 12V going to each segment with 3 in series and a current limiting resister (to make ~3" tall digits), looks like now won't need to run power at all, but have the 3 in parallel instead (need <2mA per LED to be really bright, they are capable of 10,000 mcd at 20mA, just blinding!).
(hmm, could I buffer that if needed when the device acts as both current source & sink?)

Would LedControl work for the MAX6951 as well? I am still digesting its datasheet (slowgoing after an evening of fencing) and just stumbled across the LedControl site in the playground. I am thinking I may need some more setup commands.
Any one have experience with this chip? Searching the forums hasn't yielded anything yet.
I also ordered some QSOP to DIP adapters so I could put the part on a protoboard to start with. Am thinking soldering 0.025" spaced leads will be an interesting experience. Unfortunately that's the only package it comes in.

MAXIM seems to have a lot of code available also,

looks like some assember to Arduino code translating could be in my future also - always fun coming from a hardware background!

Programming so far with Aruino has been limited to picking 6 bits out of a serial stream and driving 6 outputs high & low accordingly to turn LEDs on, and writing to 6 outputs then creating a clock to write data into an external register. Looking into writing into a shift register next, using the shiftout command. I have some 74LS195s I will play with tonight. Am thinking the display could be jittery unless I turn off the 7447s whie the data is shifting.

Thanks
Robert

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Got the MAX6951 samples from MAXIM, dang that QSOP package is tiny! Like half the size of your pinky fingernail. Ordered some QSOP to DIP adapters also, no way can I solder that little thing tho.

I also got some MAX6953 samples, nice 40 pin DIP package, much easier to work with :). Have 4 LITEON LTP2057 5x7 LED matrix chips that I am starting to hook up. They take up a lot of breadboard space! So much so that only 1 connector space next to each pin is free, rest are covered up.
Went thru the 6953 datasheet last night, got some code written to try and drive it. Need a couple more setup things to set the config register and one one register, forgot to add them as I was sorting out missing right brackets.
Don't know if ShiftOut will work or not. From the data sheet looks more like a latch function to write bits out vs a clock (edge) function.
Need to pull data line line before clock starts up to put the 6953 into data accepting mode, similar at end to go into Stop state, so some extra pinbit writes may have to be added at start & stop to get the 6953 into the correct states.
May have to pull out a scope & check out what really comes out.

DPScope.com has a nice little $89 dual channel scope you assemble yourself that runs on a laptop, makes for a nice little storage scope. Have used it to troubleshoot another arduino project as well, checking out what clock lines were doing (or not).
Robert