Hey there, I could use some troubleshooting help with this. I have a build that uses an Arduino Nano, two led's, a piezo buzzer, an 8x64 Dot Matrix LED Display Module, and a 134.2K AGV RFID Reader. This is the type of RFID reader for animal microchips and I'm using it on a build that interacts with my dogs. More for a personal POC to see what I can do with it.
My issue is that the RFID Reader range drops in half when the dot matrix is connected. So basically, without the Dot Matrix, the range on my reader is great, exactly what I need. If I turn it off, plug in the Dot Matrix, everything works as expected, but the range cuts down significantly.
This is my first more-complex build with more than one power supply, but I'm thinking this is because there's a drop in current to the RFID Reader, right? I'm confused why that would happen when they don't share the same power supply as the RFID Reader is on its own 9v battery, while everything else is on the 5v power supply from the microcontroller. I've looked all over for why this might be happening, but can't seem to figure it out, so I thought I would reach out to the community for help.
Thanks, y'all. Below is a schematic I made with some of the more obscure pieces pasted in as photos. The RFID reader and Dot matrix are both linked above for reference.
I'll also post my code below, even though I don't think it's as relevant. To give you a brief overview, my loop is constantly looking for a RFID signal. When it gets one, it reads it, parses it into a decimal ID, then checks it against my hard-coded decimal values for my dogs. Depending on which dog (or a test chip I have) it picks up, it will flash a light for that dog, display their name on the LED matrix, and play a song from the piezo buzzer.
/*************************************************
NOTE FREQUENCYS
*************************************************/
#define B0 31
#define C1 33
#define CS1 35
#define D1 37
#define DS1 39
#define E1 41
#define F1 44
#define FS1 46
#define G1 49
#define GS1 52
#define A1 55
#define AS1 58
#define B1 62
#define C2 65
#define CS2 69
#define D2 73
#define DS2 78
#define E2 82
#define F2 87
#define FS2 93
#define G2 98
#define GS2 104
#define A2 110
#define AS2 117
#define B2 123
#define C3 131
#define CS3 139
#define D3 147
#define DS3 156
#define E3 165
#define F3 175
#define FS3 185
#define G3 196
#define GS3 208
#define A3 220
#define AS3 233
#define B3 247
#define C4 262
#define CS4 277
#define D4 294
#define DS4 311
#define E4 330
#define F4 349
#define FS4 370
#define G4 392
#define GS4 415
#define A4 440
#define AS4 466
#define B4 494
#define C5 523
#define CS5 554
#define D5 587
#define DS5 622
#define E5 659
#define F5 698
#define FS5 740
#define G5 784
#define GS5 831
#define A5 880
#define AS5 932
#define B5 988
#define C6 1047
#define CS6 1109
#define D6 1175
#define DS6 1245
#define E6 1319
#define F6 1397
#define FS6 1480
#define G6 1568
#define GS6 1661
#define A6 1760
#define AS6 1865
#define B6 1976
#define C7 2093
#define CS7 2217
#define D7 2349
#define DS7 2489
#define E7 2637
#define F7 2794
#define FS7 2960
#define G7 3136
#define GS7 3322
#define A7 3520
#define AS7 3729
#define B7 3951
#define C8 4186
#define CS8 4435
#define D8 4699
#define DS8 4978
#define Silence 0
// DEFINITION FOR LED MATRIX
#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
#define MAX_DEVICES 8
#define CS_PIN 3
// FOR THE PIEZO:
#include <LowPower.h>
#include <Wire.h>
// FOR THE LED MATRIX DISPLAY:
#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>
MD_Parola ledMatrix = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);
int val; // variable for analogread piezo
int knockPin = 2; //interrupt on pin 2 or 3
volatile int interruptSwitch = 0;
int redLedPin = 7;
int blueLedPin = 8;
int lastPin1State,lastPin2State;
int anastasiaMelody[] = {
FS4, G4, FS4, A4, G4, E4, G4, E4, FS4, D4, B3, E4, FS4,
FS4, G4, FS4, FS4, B4, E4, G4, E4, FS4, D4, B3, CS4, D4, B3,
};
// note durations: 2 = whole note, 3 = dotted half note, 4 = half note, 8 = quarter note, 16 = eighth note, etc.:
int anastasiaNoteDurations[] = {
4, 8, 3, 4, 8, 3, 4, 8, 6, 16, 8, 3, 3,
4, 8, 3, 4, 8, 3, 4, 8, 6, 16, 8, 4, 8, 3
};
int gotMelody[] = {
G4, C4, DS4, F4, G4, C4, DS4, F4, G4, C4, DS4, F4, G4, C4, DS4, F4,
G4, C4, E4, F4, G4, C4, E4, F4, G4, C4, E4, F4, G4, C4, E4, F4,
G4, C4, DS4, F4, G4, C4, DS4, F4, D4,
};
// note durations: 4 = quarter note, 8 = eighth note, etc.:
int gotNoteDurations[] = {
8, 8, 16, 16, 8, 8, 16, 16, 8, 8, 16, 16, 8, 8, 16, 16,
8, 8, 16, 16, 8, 8, 16, 16, 8, 8, 16, 16, 8, 8, 16, 16,
3, 3, 16, 16, 4, 4, 16, 16, 1,
};
int testMelody[] = {
C5
};
// note durations: 4 = quarter note, 8 = eighth note, etc.:
int testNoteDurations[] = {
32
};
int unknownMelody[] = {
C2, C2,
};
// note durations: 4 = quarter note, 8 = eighth note, etc.:
int unknownNoteDurations[] = {
8, 2,
};
int anastasiaMelodyLength = sizeof(anastasiaMelody)/sizeof(anastasiaMelody[0]);
int gotMelodyLength = sizeof(gotMelody)/sizeof(gotMelody[0]);
int testMelodyLength = sizeof(testMelody)/sizeof(testMelody[0]);
int unknownMelodyLength = sizeof(unknownMelody)/sizeof(unknownMelody[0]);
int tempo = 2100;
// interrupt function
void Interrupt ()
{
interruptSwitch = 1;
detachInterrupt (knockPin);
}
char message[35];
unsigned long lastSignal = 0;
bool transmission = false;
byte state = 1;
int pos;
unsigned long testCard = 2152500911;
unsigned long picaId = 2855817755;
unsigned long theoId = 2861165065;
void setup() {
Serial.begin(9600);
lastSignal = millis();
ledMatrix.begin();
ledMatrix.setIntensity(0);
ledMatrix.displayClear();
pinMode(13, OUTPUT);
pinMode(redLedPin, OUTPUT);
pinMode(blueLedPin, OUTPUT);
ledMatrix.setTextAlignment(PA_CENTER);
ledMatrix.print("PRESENTING:");
}
void loop() {
switch (state) {
case 1: {
if (Serial.available() > 0) {
lastSignal = millis();
pos = 0;
state = 2;
}
break;
}
case 2: {
// Reading of message
if (Serial.available() > 0 && pos < 35) {
lastSignal = millis();
message[pos] = Serial.read();
pos++;
}
if (millis() - lastSignal > 100) {
state = 3;
}
if (pos >= 35) {
delay(300);
state = 1;
}
break;
}
case 3: {
// checksum
Serial.println();
byte check = message[1];
for (int i = 2; i < 27; i++) {
check = check ^ message[i];
}
Serial.println();
if (check == message[27]) {
unsigned long id = hexInDec(message, 1, 10);
int countryNbr = hexInDec(message, 11, 4);
Serial.print("CardNumber=");
Serial.println(id);
Serial.print("Country=");
Serial.println(countryNbr);
if (id == testCard) {
Serial.println("Test Card Scanned");
ledMatrix.setTextAlignment(PA_CENTER);
ledMatrix.print("TEST OK");
blinkLedTest(blueLedPin, redLedPin);
for (int thisNote = 0; thisNote < testMelodyLength; thisNote++) {
int noteDuration = tempo / testNoteDurations[thisNote];
tone(2, testMelody[thisNote], noteDuration);
int pauseBetweenNotes = noteDuration * 1.30;
delay(pauseBetweenNotes);
noTone(8);
}
delay(1000);
ledMatrix.print("PRESENTING:");
}
else if (id == picaId) {
Serial.println("Pica Scanned");
ledMatrix.setTextAlignment(PA_CENTER);
ledMatrix.print("PICA");
blinkLed(blueLedPin);
for (int thisNote = 0; thisNote < anastasiaMelodyLength; thisNote++) {
int noteDuration = tempo / anastasiaNoteDurations[thisNote];
tone(2, anastasiaMelody[thisNote], noteDuration);
int pauseBetweenNotes = noteDuration * 1.30;
delay(pauseBetweenNotes);
noTone(8);
}
ledMatrix.print("PRESENTING:");
}
else if (id == theoId) {
Serial.println("Theo Scanned");
ledMatrix.setTextAlignment(PA_CENTER);
ledMatrix.print("THEO");
blinkLed(redLedPin);
for (int thisNote = 0; thisNote < gotMelodyLength; thisNote++) {
int noteDuration = tempo / gotNoteDurations[thisNote];
tone(2, gotMelody[thisNote], noteDuration);
int pauseBetweenNotes = noteDuration * 1.30;
delay(pauseBetweenNotes);
noTone(8);
}
ledMatrix.print("PRESENTING:");
}
else {
Serial.println("Unrecognized ID Scanned");
ledMatrix.setTextAlignment(PA_CENTER);
ledMatrix.print("UNKNOWN");
for (int thisNote = 0; thisNote < unknownMelodyLength; thisNote++) {
int noteDuration = tempo / unknownNoteDurations[thisNote];
tone(2, unknownMelody[thisNote], noteDuration);
int pauseBetweenNotes = noteDuration * 1.30;
delay(pauseBetweenNotes);
noTone(8);
}
ledMatrix.print("PRESENTING:");
}
state = 4;
}
break;
}
case 4: {
delay(2000);
state = 1;
break;
}
}
}
void blinkLed(int pin) {
digitalWrite(pin, HIGH);
delay(500);
for(int i = 0; i < 3; i++) {
digitalWrite(pin, LOW);
delay(100);
digitalWrite(pin, HIGH);
delay(100);
}
digitalWrite(pin, LOW);
}
void blinkLedTest(int pin1, int pin2) {
digitalWrite(pin1, HIGH);
digitalWrite(pin2, HIGH);
delay(500);
for(int i = 0; i < 3; i++) {
digitalWrite(pin1, LOW);
digitalWrite(pin2, LOW);
delay(100);
digitalWrite(pin1, HIGH);
digitalWrite(pin2, HIGH);
delay(100);
}
digitalWrite(pin1, LOW);
digitalWrite(pin2, LOW);
}
unsigned long hexInDec(char message[], int beg , int len) {
unsigned long mult = 1;
unsigned long nbr = 0;
byte nextInt;
for (int i = beg; i < beg + len; i++) {
nextInt = message[i];
if (nextInt >= 48 && nextInt <= 57) {
nextInt = map(nextInt, 48, 57, 0, 9);
}
if (nextInt >= 65 && nextInt <= 70) {
nextInt = map(nextInt, 65, 70, 10, 15);
}
if (nextInt >= 97 && nextInt <= 102) {
nextInt = map(nextInt, 97, 102, 10, 15);
}
nextInt = constrain(nextInt, 0, 15);
nbr = nbr + (mult * nextInt);
mult = mult * 16;
}
return nbr;
}
EDIT: Accidentally initially posted this to the wrong forum
