I spent some time looking for basic requirements when using this module. Couldn't find anything.Here's how I got a display in working order. It needs some tweaks to work well.Not sure where to post this kind of info. Feel free to repost it or remove it.Thanks.MarkHope this helps those using this module.8x8 LED max7219 fc-16 hardware modulesI was having all kinds of interment problems and made the same basic changes and bam no problems. Thanks for the post. What I like about these modules is that they provide a display thatcan be seen from a distance. But there are a couple requirementsto get them working well. I'd always use an external power supply.There's 64 LED's in each matrix. If they draw 10ma each, that's atotal of 640ma for only one matrix when every LED is on. They needa power supply for reliable, consistent operation. It's not optional.Just spent a couple hours sorting out hardware issues on these.They are picky about ground connections. And they need filter caps.I will not spend any time to isolate every detail of their operation.In any case I would recommend soldering an electrolytic filter capacross Vcc and GND at the top of each module. At least 1uF, orlarger. I used what I had on hand. It's a prototype. Max7912drivers generate switching currents when driving LED's. Filter capshelp reduce voltage spikes that will interfere with control signals.Random and intermittent operation results without them, depending onhow many LED's are being driven.These two requirements are not optional for any hope of hardwarestability. What follows is not as critical.I soldered all connectors across a 10 matrix display. Vcc and GNDwere all soldered with separate leads to an external power source.Each module has its own Vcc and GND lead to the power source. Theseare NOT wired in series like the original configuration. Parallel.Signal wires (3) must be connected in series from the bottom of onemodule to the top of the next module. This is standard configuration.I soldered all of these connections. DIN, CS, CLK.Then, all the bottom Vcc connections are left open and all bottomGND connectors are soldered to a single wire, in series, which isthen connected to an UNO GND pin.Since making these mods, hardware issues are resolved. There areprobably other ways to address hardware issues, but these mods workwell for me.MaxMatrix code has to be edited when writing to more than ninemodules. At least for the revision that I found online. Everywherethere is an '80' or '81' in the .h or .cpp file I changed to avalue of '88'. It now writes to ten modules connected in series.If you add more modules, keep increasing these numbers until itwrites correctly. I did not go through all the code, so I can'tsay how this works, exactly. There's almost no comments in thecode, and I don't want to spend any more time on it.I have not had any trouble working with my display since making thesemods. I'm using a total of ten (10) FC-16 modules.There's no substitute for a soldering iron. And I might add aresistor here and there in signal lines if any other hardware issuescrop up. It's always a good idea to add current limiting resistorson all signal pins/ports of your Arduino. There's nothing quite likestable hardware, and it's seldom mentioned. (I see these issues quitea bit watching youtube video.) It makes coding that much easier.Again, I really like these modules for a display. They just need alittle help to get them working well. It's hard to complain aboutprice, and there's a number of ways they can be configured fordisplay purposes -that you can see across the room-. 64 outputs foreach matrix. In combinations, many more than that. Kinda cool.Then, there's SPI applications... Later.
I didn't read through your entire dissertation.