MAX7219 8 digit 7 segment display, Arduino Mega and Ethernet Shield

Projects Programming
1

The title should state what I am using, I have an Arduino Mega, that is using the Ethernet Shield for aRest commands, and I want to add the MAX7219 8 digit 7 segment display to it. However the code example shows that it uses Pin 12,11,10 which are in use by the ethernet shield.
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A little help would be greatly appreciated. Thank you so very much!!

2

The MAX7219 uses a a shift register interface that can use any pins you want. Just put the ones you want when you define it. The SPI interface uses a specific set of hardware pins, but the MAX7219 library (at least the one I use) doesn't use the hardware support.

5

It appears when I add the ethernet shield libraries and initialize the ethernet shield (despite putting the Max7219 on pins 47, 49, 51). The Max7219 will no longer respond. I replicated this with my code and with the demo by adding in piece by piece of my code, after it initialized the ethernet shield.... no lights on the max7219.

Any ideas?

6

51 on the MEGA is a pin which is used also for SPI.
you could either use another pin or you use a library which has also the possibility to use HW-SPI.

For example my MAX7219 library:
https://werner.rothschopf.net/201904_arduino_ledcontrol_max7219.htm

it works on any pin or with the HW-SPI - which is preferred anyway.
See the example "LCDemoNoiascaHelloWorldSPI "

constexpr uint8_t ledCSpin = 8;            // 8 LED CS or LOAD -  8 CS
// you don't need to define CLK         - 13 CLK  on UNO/NANO - 52 on MEGA
// you don't need to define LED DATA IN - 11 MOSI on UNO/NANO - 51 on MEGA
constexpr uint8_t ledModules = 1;          // how many MAX72xx are connected

This works for sure on a Mega with an Ethernet/SD shield.

7

Thank you for this.... thank you for this.... I feel like an idiot. Got it most of the way working for now.