2 8x8 Led matrix with MAX7219 and Teensy 3.2

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mariano

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Hello everyone,

I'm having a hard time finding information about how to properly power supply 2 8x8 led matrix (16x8) with the MAX7219 from a Teensy 3.2.
As you may know, the MAX7219 needs 5V to work (datasheet says it may work with 3.3, but they cant tell for sure), and teensy outputs 3.3v.
I saw some solutions where an external power supply is used to power up the led matrix and then the USB cable to power up the board, but i want to use only 1 power supply (or cable) to power up everything.

I'm using this module
C8ssVJ6.jpg



how can this be done?
 
Power the MAX7219 with 5V. It can accept 3.3V signals on its 3 input pins.

Please be aware some MAX7219 chips are Chinese counterfeits. Buyer beware.
 
Power the MAX7219 with 5V. It can accept 3.3V signals on its 3 input pins.

Please be aware some MAX7219 chips are Chinese counterfeits. Buyer beware.

Hi Paul,

So, if i power the 7219 with 5V, how can i use that same input to power up the teensy?
Do i need to use 1 power supply for the leds and another for the teensy?
 
The Teensy 3.2 has an onboard reg, so you have a 5V power supply for the matrix and the Teensy connected to Vin pin. Teensy regulates 3.3V internally and provides it on the 3.3V pin should you happen to have any low current hardware that needs it.
 
I made them work (kind of) :)
Still something doesn't fit.

Leds go fine from 1 to 7, but then, on the last step it skips the last column of the first matrix (colum 8) and jumps to column 16 (column 8 on the second matrix)
I tried modifying the library but didn't helped.
VIDEO: https://youtu.be/8j-KHbhmXWc


Screen Shot 2017-06-24 at 11.01.58 PM.png

I'm using this code to test both matrix:
#include <Sprite.h> // Sprite before Matrix
#include <Matrix.h>

const int numChips = 2;

// DIN, CLK, LOAD, #chips
Matrix myLeds = Matrix(2, 4, 3, numChips);

void setup() {
myLeds.clear();
}

void loop() {
byte x, y;

// light one LED at a time, scanning left to right
// and top to bottom... useful for testing the matrix
for (y=0; y<8; y++) {
for (x=0; x<(numChips * 8); x++) {
myLeds.write(x, y, HIGH);
delay(100);
myLeds.write(x, y, LOW);
}
}
}




Just in case anyone gets here with the same doubt, ill share what i did.

Teensy 3.2 with 2 chained Led Matrix 8x8 Modules with MAX7219ENG (The one in the first post)

I separated the VUSB pad and then just connected the 5V input to VIN pin and ground to the external ground.
After that, i connected the Led matrix to 5V directly, and then connected the other pins (gnd, din, cs, clk) to teensy (GND,2,3,4)

After that, i tested both matrix with the code mentioned above
 
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