Serial communication between esp32-cam and Arduino Uno

Using Arduino Programming Questions
1

I was trying to send some data from esp32-cam to Arduino Uno. So I was try this code for Esp32-cam

#include<Wire.h>
int hour=12;
void setup() {
  Wire.begin();
  Serial.begin(115200);
}
void loop() {
  Wire.beginTransmission(9);//9 here is the address of the slave board
  Wire.write(hour);//Transfers the value of potentiometer to the slave board
  Wire.endTransmission();
  Serial.print(hour);
  delay(1000);
}

And code for Arduino Uno:

#include<Wire.h>
int hour;
void setup() {
  // Begin the Serial at 9600 Baud
  Wire.begin(9);
  Serial.begin(15200);
  Wire.onReceive(receiveEvent);
}
void receiveEvent(int bytes) {
  while (0 < Wire.available()) {
    hour = Wire.read();
  }
}
void loop() {
  Serial.print(hour);
  delay(1000);
}

But this code not working for me. I also trying some other way. But none of them work.

Any idea, hints will be appreciate.

2

The UART serial port is a lot easier to use than I2C.

I believe that Wire.onReceive() is an interrupt handler, so "hour" must be declared volatile.

3

Hi

show us the wiring and how they are powered

As one is 3.3V the other is 5V - do you have an I2C voltage adapter?

4

I connect the
Tx pin of esp32-cam to Rx Arduino Uno
Rx pin of esp32-cam to Tx Arduino Uno
And a common ground GND.

No ,I don't use .

How I can do this?

5

See the "Serial Input Basics" tutorial on the forum.

6

is your ESP 5V compatible ? (arduino Tx can send 5V into ESP Rx)

and Rx and Tx are not the I2C pins...

7

This COULD be the mistake

8

@jremington
I tried all of them. They works for two Arduino but not for Esp32-cam and Arduino.

9

It works perfectly for me.

I don't know what you did wrong, so can't offer anything more, except to ask whether you used level shifters, as required for connecting 5V and 3.3V modules.

1 Like
10

@jremington
Can you explain how it works for you?
Means have you any example that works for you?

11

I use Serial.print() on the ESP32, and Serial.available() + Serial.receive() on the Arduino.

With a 5V to 3.3V level shifter, of course.

Did you connect TX on one to RX on the other, using the level shifter?

1 Like
12

No, I don't. May be this is the issue I have mistake.
Ok, I will try using the level shifter. Then give you feedback.

13

You may have permanently damaged either the Arduino or the ESP32.

You must not directly connect a 5V signal to a 3.3V input. The other way around (3.3V output to 5V input) is usually, but not always OK.

1 Like
14

@jremington

One things is Esp32-Cam also have a 5v input. So if I use 5v input for Esp32-Cam then is it necessary to use level shifter?

If level shifter is must, then is this level shifter will work for me?
image

I want to send data from Esp32-Cam to Arduino.

15

That is for power, to a voltage regulator. The MCU is 3.3V only.

1 Like
16

Ok. Thanks.

I got it. Is this level shifter work for Esp32-Cam?

17

That kind of level shifter will work.

18

this one worked for me without a level shifter
the esp code


#include "string.h"

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}
void loop() {
String cmd ; 
    //Serial.println("Message Received: ");
   cmd = Serial.readString();
   delay(5);
   Serial.println(cmd) ; 
   delay(5);
    Serial.write("Message Received"); 
    delay(5);
     Serial.println();
}

and the arduino code

#include <SoftwareSerial.h>
#include "string.h"
SoftwareSerial SoftSerial(4, 5);


void setup() {
  Serial.begin(9600);
   SoftSerial.begin(9600);
}
void loop() {
  String cmd;
  SoftSerial.write("Hello Boss"); 
  cmd = SoftSerial.readString() ; 
  Serial.println(cmd);
  delay(500);
}
19

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