Can't change 7 segment display

[jsureke]

I can get the MAX7219 to initially put numbers on the 7 seg digits, but if I change any value it either turns completely off or completely on (all lights lit 8.8.8.8.8.
I tried to make a timer that counts seconds, but it turned off, then on, then off, etc. every second.
There must be something to do besides calling setDigit.
Where can I look for an example?

[PaulStoffregen]

Where can I look for an example?

In Arduino, click File > Examples > LedControl > LCDemo7Segment

[jsureke]

That doesn't even work. It starts working but it doesn't show all the changes and it doesn't loop a second time. I must have faulty components.

[Frank B]

Quite possible that it is just a problem with the connections.
If we had a photo, we could take a look

[jsureke]

a problem with the connections

I just learned that the chip is really finiky.

a problem with the connections.If we had a photo, we could take a look

This prototype isn't the best looking solder job. I'm just going to start over.

[PaulStoffregen]

Which Teensy are you using? (if I were to dig out my MAX7219, which one should I test....)

[jsureke]

Which Teensy are you using?

I have a Teensy 3.5 and an Arduino Mega. Multiple boards, multiple sketches, alll with the same results, so it has to be the hardware.
I do know that I didn't use the capacitors on the 5v that some people say are needed, so I'm scrapping all of this and starting over, but I'm using a socket this time, so I don't kill my chip. Not that they are all that expensive, but waiting on delivery is a pain.

[PaulStoffregen]

I found that old MAX7219 test board, plugged in a Teensy 4.1, and ran the LCDemo7Segment example.

It seems to work fine...

[PaulStoffregen]

I have a Teensy 3.5 and an Arduino Mega. Multiple boards, multiple sketches, alll with the same results, so it has to be the hardware.

Yup, probably hardware.

Since it was still on my workbench, I plugged in a Teensy 3.5 just to make sure.



On this test board the MAX7219 runs from VIN (5V). There are only 5 wires between the MAX7219 and Teensy: 5V, GND, and 3 signals. The MAX7219 seems to do fine with the 3.3V signals when running from only 5V.

[defragster]

I just got one of these :: protosupplies.com/product/max7219-8-digit-7-segment-socketed-red-display-module/


Plugged into a T_4.1 it is working with :: ...\hardware\teensy\avr\libraries\LedControl\examp les\LCDemo7Segment\LCDemo7Segment.ino

Had to extend the running digits to cover all 7 - but it is working. Also 5V VIN and data/control lines from 3.3V T_4.1.