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Topic: Scrolling text on LED matrices using SPI and arduino Mega2560 (Read 8 times) previous topic - next topic

Aaron_dyer

Taken from the Playground site we are mentioning here...I have it in my posting about the scrolling on matrices.....


"By no means these 2 capacitors can be ommitted (Left out), as it might lead to sporadic or permanent malfunctions. These types of errors are really hard to track down. Both capacitors must be placed as near as possible to the V+ and the Gnd pins of the MAX72XX. "


I need to re place the caps closer.....and not just on Vcc and ground planes.....

Aaron_dyer

Now I'm getting conused again......

this is taken from the playground website:

"If you read the datasheet for the MAX72XX you know that the drivers can be cascaded by simply connecting the signal DOut from one chip to DIn on the next chip. The signals Clk and Load(/CS) have to be connected  in parallel to each MAX72XX. There is no strict limit as to how many drivers can be cascaded that way."

I don't have the Loads connected in parallel...they are set up from ss0-ss3 individually from the arduino I/Os  53, 49, 48 and 47......

CrossRoads

Move the clear digits to immediately after the SPI.begin();

This chunk of code at the end of setup will leave display test on = all LEDs on:

byte display_test = 0x0F;           // 0x00 = normal, 0x01 = display test mode all on full

Code: [Select]

  // dispay test to normal
  digitalWrite (ss0, LOW);
  SPI.transfer (display_test);
  SPI.transfer (0x01);
  digitalWrite (ss0, HIGH);

I would put in a brief delay, and then set this register to 0 to turn it off.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Aaron_dyer

is there anyway you could take the code I pasted before and update it with your updates and repost it.....I'm starting to lose track of everything...I'd appreciate it....


Also one thing I need to be certain of.....

imagine you have your 4 matrices  going from left to right with each having the max7219 under them.....

the first max7219 that needs to be interfaced from the arduino is farthest to the right then going from right to left correct? Or is it farthest to the left going to the right.....

I know I'm blowing up these forums...I just want to get this right....


CrossRoads

#0 is on the left, #3 is on the right.
I'll see if I can fix the code up.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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