How to control 2 LED matrix (MAX7219) using potentiometer

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1

Hello all, I'm new to Arduino and coding. I am trying to light up the LEDs of two 8x8 matrix using a potentiometer. Matrix1 will light up when the pot value ranges from 0 to 500, and another matrix will glow when the pot value ranges from 500 to 1023. I have tried with one LED matrix and need some guidance on connecting the second matrix and making it working.

Here I have given the code for single LED matrix
Code:

#include <LedControl.h>
int DIN = 11;
int CS =  10;
int CLK = 13;
LedControl lc=LedControl(DIN,CLK,CS,2);

void setup(){
 lc.shutdown(0,false); 
 lc.setIntensity(0,50);
 lc.clearDisplay(0);
}
void printByte(byte character []){
  int i = 0;
  for(i=0;i<8;i++){
    lc.setRow(0,i,character[i]);
  }
}

void loop(){ 
  byte cero[8] = {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00};
  int value = analogRead(A0); // read of potentiometer value
  int scale = map(value, 500, 1000, 0, 13); // map function to get brightness

  for (int i=0;i<scale;i++){
    cero[i] = 0xff;
  }

  printByte(cero);

  delay(100);
}
2

Welcome to the forum

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3

Why 500? 512 each side would be even... (0 - 511), (512 - 1023)

I think the first value (0) is the panel number... so the second panel will be (1).

This is how to set/reset one LED in a panel...

lc.setLed(0, 0, 0, state); // panel 0, x = 0, y = 0, ON/OFF

Connecting the panels...
VCC - VCC
GND - GND
DOUT - DIN (data moving left to right)
CS - CS
CLK - CLK

I see how moving the potentiometer on A0 "lowers" and "raises" the LEDs... what is the pattern you want reflected on panel 1?

I think this might be what you had in mind... I added comments...

#include <LedControl.h>
int DIN = 11;
int CS =  10;
int CLK = 13;
LedControl lc = LedControl(DIN, CLK, CS, 2);

void setup() {
  Serial.begin(115200);
  lc.shutdown(0, false);
  lc.setIntensity(0, 50);
  lc.clearDisplay(0);
}

void printByte(byte character [], int panel) {
  int i = 0;
  for (i = 0; i < 8; i++) {
    lc.setRow(panel, i, character[i]);
  }
}

void loop() {
  int panel; // which panel to use
  byte cero[8] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
  int value = analogRead(A0); // read of potentiometer value
  int scale = map(value, 0, 1023, 0, 17); // 16 rows, plus one

  if (value > 512) { // if raw potentiometer is above middle, use panel 0, subtract 8 for row 
    panel = 0;
    scale = scale - 8;
  } else { // if raw potentiometer is below middle, use panel 1, subtract row from 8
    panel = 1;
    scale = 8 - scale;
  }
  for (int i = 0; i < scale; i++) {
    cero[i] = 0xff;
  }
  printByte(cero, panel);
  // delay(100);
}
Put this file in WOKWI.COM diagram.json tab 
{
  "version": 1,
  "author": "Anonymous maker",
  "editor": "wokwi",
  "parts": [
    { "type": "wokwi-arduino-nano", "id": "nano", "top": 4.8, "left": -86.9, "attrs": {} },
    {
      "type": "wokwi-max7219-matrix",
      "id": "matrix1",
      "top": -143.4,
      "left": -110.18,
      "attrs": { "chain": "2" }
    },
    { "type": "wokwi-potentiometer", "id": "pot1", "top": -10.9, "left": 134.2, "attrs": {} }
  ],
  "connections": [
    [ "nano:11", "matrix1:DIN", "green", [ "v-57.6", "h163.2", "v-38.4" ] ],
    [ "nano:10", "matrix1:CS", "green", [ "v-48", "h144", "v-38.4" ] ],
    [ "nano:13", "matrix1:CLK", "green", [ "v-96", "h153.6", "v-38.4" ] ],
    [ "matrix1:GND", "nano:GND.2", "black", [ "h38.4", "v96", "h-76.8" ] ],
    [ "nano:5V", "matrix1:V+", "red", [ "v19.2", "h86.4", "v-211.2" ] ],
    [ "pot1:GND", "nano:GND.1", "black", [ "v19.2", "h-105.6" ] ],
    [ "pot1:VCC", "nano:5V", "red", [ "v28.8", "h-144.8" ] ],
    [ "nano:A0", "pot1:SIG", "green", [ "v28.8", "h201.6" ] ]
  ],
  "dependencies": {}
}
4

Thank you so much; this is what I am really trying for.

5

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