Look what I found…
I think these are relatively new to Aliexpress. Unlike the ‘previous generation’ that had DIP types chips, these boards have surface mount MAX7219s and fit up against each other, making it much easier to build big displays.
Next step is to connect this to an ESP8266. I’m just wondering if it will work without a level converter - if I’m right these are 5v and the ESP8266 is 3.3v…?
Might work in the 3.3 to 5 direction but probably not the other way , you will have to take a close look at the datasheets.
But if it’s not going to be put into mass production in my experience it’s always best to dot the I’s and cross the T’s and put in a level converter.
I don’t think any signals go from the display to the microcontroller.
I might try running the display at 3.3v first and see what happens.
Might work but in my opinion it is still not a very good idea in a system with led’s being scanned and mobile phones in the room. For the sake of 50p worth of transior .
But I have worked in EMC and thus I worrey about this sort of thing
Thinking that the levels are compatible. But be careful with you grounds as you are given up a lot of headroom
The MAX7219 is a great chip, used it on matrix’s and 7 Seg displays but mainly with Arduino.
Apparently it should work on ESP8266 but officially a logic high on the MAX7219 is 3.5v so it could be a bit random without a level converter.
The MAX6951 is the new 3.3v version of the MAX7219 but that won’t help on a built in version 
Courty
It’s good to see somebody bothered to read the datasheets. …
That’s a shame. A lot of modern stuff is 5v tolerant with a 2v logic high so 3.3v to 5v stuff is often not an issue.
I assumed that would be the case…
Just found a 8x8 MAX7219 matrix in the ‘box of bits’, will hook it up to the ESP8266 NodeMCU later if I get a minute !
Courty