Display for Arduino

[SillyOldDufferModerator @sillyoldduffer]

Posted by Ady1 on 27/11/2020 16:12:35:

I sent the 5v live and ground to the breadboard and connected the modules from there, the 7219 first

The 7219 is greedy because it's 100s of LEDs

Does negatives too

edit: must confess that the outputs look weird to me, 100.5 is 10.05 kgs perhaps… hmmm

Just noticed sods post… oops

well if you get the led one it works ok… ish

my brain has exploded so I'll look at calibration testing later

Can you post a picture of your working Parola Display Ady? Then we can see the difference between Peter's 7 segment display and a 16×16 display.

What confused all of us is both types of display are driven by the same MAX7219 chip. It didn't work because the LEDs are wired differently to the 7219 so the commands sent to create visible characters on the two displays are incompatible.

Peter's Adafruit display uses the #include <HCMAX7219.h> library, while Ady's display uses #include <MD_Parola.h> (which behind the scenes depends on the MD_MAX72XX library, supporting 7219 and 7222 LED drivers. )

Peter bumped into the need to check everything!

• The display was wired correctly to power and the SPI pins
• His program was logically and syntactically correct
• The program loaded and ran correctly on the Arduino, meaning Peter's serial link and processor selections were correct.
• The program does not cause 'undefined behaviour' due to consuming too much memory, ie Peter's code wasn't a resource hog or running amok.
• Peter's 7 segment display failed only because it doesn't understand 16×16 commands sent by the Parola library.

All the bother was caused by a simple mistook at the beginning : Peter's chosen library didn't match the hardware.

Ady's mention of the 16×16 display guzzling power reminded me of another problem, fortunately it didn't happen here. There's a chance the bootloader will malfunction whilst burning a new program if the Arduino's power supply is heavily loaded by connected devices, The cure is to connect power greedy devices after loading the new program, or to power them separately.

Dave

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