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Topic: MAX7219 in daisy chain. How many decop capacitors I need? (Read 4586 times) previous topic - next topic

Riva


"when I turned the board over to the front that the columns were now backwards"
But you can fix that in software - swap the bytes end for end that go to the max7219 registers:
Data intended for Register1 goes to Register8, and data for Register8 goes to Register1 instead.

This happened months ago. I just swapped the order of the 8 wires, only took a couple of minutes.

Aaron_dyer

Riva,

I uploaded your ScrollTest4  code....

This is the run in I'm having with my mega2560.....

so for this one I have the Duemilanove running....

but the text is scrolling vertical and the letters are backwards.....

man this is so frustrating..

I'm just using 1  max7219 and 1 matrix right now......


I wire my components up via this site:

http://www.pjrc.com/teensy/td_libs_Matrix.html

My matrices say XH-1088BRW  on them as well......

Pedro147


so the matrices don't scroll across each other, they just all show the same letter as each individual matrix scrolls...

I did play around with two matrices and  LedControl and had this problem too. From memory (not stating fact) I had the number of devices integar set at 1 instead of 2

LedControl lc=LedControl(12,11,10,1);    12, 11 and 10  Arduino pins  1 number of Max7219.

It maybe worth checking good luck Pedro.
http://www.pedroduino.com

Riva

#33
Nov 09, 2012, 09:11 am Last Edit: Nov 09, 2012, 09:13 am by Riva Reason: 1

I wire my components up via this site:
http://www.pjrc.com/teensy/td_libs_Matrix.html

Ah, I understand now, I though you had it all wired up using this article http://www.arduino.cc/playground/Main/MAX72XXHardware but it turns out it's not.
The matrix is wired slightly different in each article so the code I suggested is no use to you. Also the pjrc version has the matrix rotated 90 degrees so this accounts for the letters scrolling the wrong way. I'm not sure why the letters would be backwards but as Crossroads points out this can easily be fixed by reversing the retrieval order of the matrix data. Now the only thing I can suggest for each matrix showing the same letter is you have them cascaded backwards. Looking from the front of your 4x matrix blocks the arduino should be connected to the right hand device (DIN, CLK & LOAD) and that MAX7219 DOUT should be connected to DIN on the MAX7219 to it's left and so on.

EDIT: Just noticed this in the pjrc article.
Quote
Beware, the Matrix library wants Teensy to connect to the last chip, and the DOUT-to-DIN chain connects from right to left. That seems backwards, but if you wire Teensy to DIN on the left-most chip as might seem intuitive, your display will end up with groups of 8 instead of one nice, continuous X-axis coordinates.

dhenry

The pjrc wiring is fairly common: you send most significant byte (left most digit) first.

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