MAX72xx chaining

Is there a limit to the number of MAX72xx LED drivers you can chain together? I was thinking of using 12.

Should be okay.
May have to buffer the clock and latch signals, maybe as 2 pairs driving 6 parts each. Data is part to part.

An alternative (to buffering) would presumably be to "bit-bang" instead of using the SPI hardware, thus slowing down the update process.

There is probably some aspect also of module construction. Presuming (with great confidence) that you are wanting to use matrix displays, there are two versions of the common modules available, the older, crude design presuming you use jumper wires to chain them and the later proper design which is compact, immediately stackable both horizontally and vertically and simply uses jumpers to chain from one to the next.

Thanks for the input. I'm going to make PCBs for the driver chips and LEDs, but before I do that I wanted to know if I could address >8 MAX7219 driver chips each one controlling two 7-segment LEDs.

Well, that poses two questions.

Given my comments regarding wiring, if you were to put them all on one PCB, I cannot guarantee whether they would work without the buffers or not.

But more to the point - one MAX7219 will control eight 7-segment LEDs (nine if you forego the decimal and mix common-cathode and common-anode displays; eight of one and one of the other), so you only require a quarter of (whatever) the number you propose! :astonished:

Paul__B:
Well, that poses two questions.

Given my comments regarding wiring, if you were to put them all on one PCB, I cannot guarantee whether they would work without the buffers or not.

But more to the point - one MAX7219 will control eight 7-segment LEDs (nine if you forego the decimal and mix common-cathode and common-anode displays; eight of one and one of the other), so you only require a quarter of (whatever) the number you propose! :astonished:

Interesting, I thought that a single MAX7219 could control up to 8 digits on a 7-sgement, so either 8 single digit LED's, 4 x 2-digit 7-segment LEDs, etc... I'm planning on controlling:

[2 + 4] digit off of 1 MAX7219, then [3 + 3] digit off of 1 MAX7219 x 5 on a single PCB

then the same on another connected (via ribbon cable) PCB. Hence 6 MAX7219 per PCB.

I was planning on addressing each MAX7219 with address's [0..11] from a driver PCB also connected to the first LED PCB via ribbon cable.

So, when you say that a single MAX7219 can control up to eight 7-segment I think you are referring to 8 digits.

" [2 + 4] digit off of 1 MAX7219, then [3 + 3] digit off of 1 MAX7219 x 5 on a single PCB

then the same on another connected (via ribbon cable) PCB. Hence 6 MAX7219 per PCB."

That reads to me as 1 MAX7219 with 6 digits arranged as displays of 2 and 4 digits,
then 5 groups of 1 MAX7219 with 6 digits arranged as displays of 3 and 3 digit.
So 6 MAX7219.
Repeat for a 2nd board.
Depending on how far apart they are, SCK/SS could go to each board and be daisy chained to all 6 parts, with MOSI going to DIN on first part and DOUT-DIN from part to part.
Both boards would update in parallel.
Or you could have a unique SS to each board and update independently.

SPI clock can be slowed down if needed.