MAX7219 breakout system

[oblique karma]

Hi,
I am trying to configure my system with a breakout board with 2 MAX7219 5 digits. I unsuccessfully followed the instructions in https://github.com/MobiFlight/mobiflight-pcbs/blob/main/max7219-breakout-system/README.md so I need some help.

In the module setup, I used pins 7-8-9 (DIN-CS-CLK). How many modules should I put here? 2 because there are 2 5-digits modules connected? Or 4 because the board offers 4 slots?

I connected one flat cable to J2 and one to J4.

After powering up (5V from external source) the digits flash shortly then stabilize as in the picture. I believe it is normal at startup. The fact that all the leds are light up let me think that cabling is correct so I think that something wrong must be in the position of the cables and/or in the setup of MF configuration.

The configuration is in the picture however if I press test the number does not show up in the digits.

Thanks for your help!

[fierce furnace]

One "module" is equivalent to one MAX7219 chip. The PCB contains 4 of them. You have up to 4 module for your project.
Each module is capable of controlling up to 8 LCD digits.
beside the plugs there are pairs of numbers:

• DIG 0-3 0-5
• DIG 4-7
  This means that the "upper" plug might be used for the digits
• 0 to 3 or
• 0 to 5
  The "lower" plug might be used for the digits
• 4 to 7
  You should configure your Hardware for 4 modules.
  The flat cable is mounted correct for up to 6 digits.

How did you connect +5V and GND?
As far as I remember the module and the Arduino should share GND. And for such a low number of LEDs the +5V from the Arduino should be sufficient, not taking too much power.

[dusty kayak]

Thanks for chiming in

Yes, look at the PCB and the connectors. One connector will drive all 8 digits of a chip. and the other connector only half. So you can share the 8 digits like @fierce furnace already explained.

@oblique karma in the device configuration for the 7-segment display you want to set the number of modules to 4

[oblique karma]

Ok guys, so it seems that I have connected the cables correctly. The flat cables are in the upper connectors (0-5 digits). The only thing that I did not do correctly is sharing the ground. Will give it another try later today.

[oblique karma]

Solved: the problem was in the connection of the board to the arduino mega. The names o the pins in the breakboard and those in the manual differ and that confused me.
In MF interface the pins are named DIN-CS-CLK, in the breakout they are labelled DIN-CLK-LOAD (i.e. CLK is in the middle!)

Hope this post will be useful for other too!! Thanks again 🙂

[dusty kayak]

you have to pay attention to the version of the board

the first version had these pins different than recent versions