8+ X MAX7219 Scroller

Projects General Guidance
1

I have tried various code for an 8x64 or more scroller but often only works for 2 'sqaures' or 4 squares not 8 or sixteen - i have edited the field 'numdevices' which works for 1 or 2 or 4 devices but makes no difference for 8 - 16
I suspect there is something in the code I don't understand

here is the best code i have been using not my own!
Hardware is a nano (or uno) and 4-16 1088as and max 7219's
I can get 4 working great but any more doesn't work
They initialise in sequence.. i can get modules on the daisy chained module to work (i have 4 modules with 4x8x8 on each) but at the expense on modules on the other unit so i don't think its power related
I have tried it with a lm7805 regulator and made no difference rather than running it all off the usb port

Really appreciate some help on this! Thanks
I've had to include code as attachment as too long

Dot_matrix_MAX7219_scroll.ino (16.3 KB)

2

Please use code tags, the symbol up and left in the Quick Reply window. Helpers using tablets, phones etc. have no IDE and can't read Your code.

3

I did! it still said too big!

just tried again and it says exceeds 9000 characters..

i've attached as txt file if that helps

New Text Document.txt (16.3 KB)

4

Sorry. You did the right thing having that large code. My mistake.

Can You post the wiring, data or links to the power supply?
I've used plenty of 7805 but I suspect Your project might need "some current", maybe too much.

5

Hi
It's running on a 10 amp variable bench psu..
I put the regulators in just in case! along with reverse polarity protect diodes as I tend to cock thinks up sometimes haha!

Bench Psu running at 7v with 0.5a current limit
470uf cap across input to regulator
0.1uf cap across output of regulator
small heatsink on regulator

output voltage from regulator is 4.85v on scope and dmm with almost no measurable ripple (Switch mode supply!)
current varies but with text on 4 modules is no more than 200ma

6

7 volt feeding a 7805 sounds a little bit low to me. I would use 7.5 - 8 volts.
Okey, 200 ma. That's safe. Is that for the maximum setup?

7

Hi thanks
I can vary the voltage in.. the reg is to protect the circuit if I accidentally change the wrong digit of the bench PSU to 30v LOL
I have measured regulator with a 5 ohm load and it provides 800ma with small sink at 7v in - gets hot but not too much
I don't think this is power related I think its code related

8

My guess on a power issue was based on the fact that things work using a small amount of loads.
Increasing the numer of power consuming devices very, very often leads to a power issue.
Can You check all voltages using the maximum setup?
I'll do the work to download Your code in the mean time.

9

Looking at Your code I find a call to a function "pgm_read_byte_near" but I don't find the function itself. That puzzles me.
Using strings is not good due to the poor garbage collection within the IDE/Arduino world. That's a suspect.

The function is used to return both byte, int and unsigned long. That's extraordinary to me.
Some help, please.

10

I'm an Arduino noob analog electronics ..
last time I wrote code was a zx spectrum lol

this is not my code so hard to fault find

Thankyou

11

Okey.
That's not good. Is there any chance You can ask the guy who once wrote that code?
I feel I have nothing more to offer You. This to odd for me.

12

I will try and find

The link in the code is dead.. hence why i'm on here

I've had similar issues with various other code designed for max7219 even with different library's and some I assume old library's wont even compile

What is the most solid max7219 library to use and learn?

13

As I suspected, the bulk of the code is a huge character storage matrix. That should really be in a separate .h file in the same sketch folder, and #include 'd in the main .ino.

There's nothing really wrong with the LedControl library that it uses. I've used it before.

14

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