Data order getting changed in I2C in ESP32 Arduino #10383
Description
Board
ESP32 Dev Module
Device Description
I am using 2 ESP32 Dev modules and a breadboard. The SDA (GPIO21) and SCL (GPIO22) of both ESP32s are connected together as well as pulled up to 3.3V using 4.7k resistors.
Hardware Configuration
Only the SDA (GPIO21) and SCL (GPIO22) of both ESP32s are connected together and pulled up to 3.3V using 4.7k resistors.
Version
v3.0.4
IDE Name
Arduino IDE
Operating System
Windows 10
Flash frequency
80MHz
PSRAM enabled
no
Upload speed
921600
Description
I programmed an ESP32 as an I2C slave. I was using arduino IDE to program the ESP32 and the version installed in the boards manager is 3.0.4. When I tested it with a master, the data order was incorrect on the received data. To test it at a very basic level, I wrote a piece of code where whatever the master wrote to the slave, the slave would return the double of it on the next data request. The issue is that, the data is delayed by one read. To understand, see the the master and slave output:
Master Output
Sent: 1, Received: 10
Sent: 2, Received: 2
Sent: 3, Received: 4
Sent: 4, Received: 6
Sent: 5, Received: 8
Sent: 1, Received: 10
Sent: 2, Received: 2
Sent: 3, Received: 4
Sent: 4, Received: 6
Sent: 5, Received: 8
Slave Output
Received from master: 1, Prepared to send: 2
Received from master: 2, Prepared to send: 4
Received from master: 3, Prepared to send: 6
Received from master: 4, Prepared to send: 8
Received from master: 5, Prepared to send: 10
Received from master: 1, Prepared to send: 2
Received from master: 2, Prepared to send: 4
Received from master: 3, Prepared to send: 6
Received from master: 4, Prepared to send: 8
Received from master: 5, Prepared to send: 10
The slave sends te correct responses but the master receives it the next time.
After working on the issue, I can say that the issue is on the slave side. I uploaded the same slave code to an arduino mega and used it with ESP32 as the master and the response is correct without the data order getting changed.
Following is the master code
#include <Wire.h>
const int slaveAddress = 0x08; // I2C address of the slave
void setup() {
Wire.begin(); // join I2C bus as master
Serial.begin(115200);
}
void loop() {
// Send numbers 1, 2, 3, 4, 5 in series
for (int valueToSend = 1; valueToSend <= 5; valueToSend++) {
sendAndReceive(valueToSend); // Send and receive for each number
delay(1000); // 1-second delay between transmissions
}
}
void sendAndReceive(int valueToSend) {
// Send the value to the slave
Wire.beginTransmission(slaveAddress);
Wire.write(valueToSend); // Send the number to be doubled
Wire.endTransmission();
delay(5000); // Small delay to ensure the slave processes the request
// Request 1 byte back from the slave
Wire.requestFrom(slaveAddress, 1);
if (Wire.available()) {
int receivedValue = Wire.read(); // Read the response from the slave
Serial.print("Sent: ");
Serial.print(valueToSend);
Serial.print(", Received: ");
Serial.println(receivedValue); // Expecting the doubled value
} else {
Serial.println("No response from slave");
}
}
The slave code is also attached
Sketch
#include <Wire.h>
int receivedValue = 0;
int responseValue = 0;
void setup() {
Wire.begin(0x08); // join I2C bus with address 0x08
Wire.onReceive(receiveEvent); // register event for receiving data from master
Wire.onRequest(requestEvent); // register event for responding to master requests
Serial.begin(115200);
}
void loop() {
}
// This function is triggered when data is received from the master
void receiveEvent(int howMany) {
if (Wire.available()) {
receivedValue = Wire.read(); // Receive the number sent by the master
responseValue = receivedValue * 2; // Double the value
Serial.print("Received from master: ");
Serial.print(receivedValue);
Serial.print(", Prepared to send: ");
Serial.println(responseValue);
}
}
// This function is triggered when the master requests data
void requestEvent() {
Wire.write(responseValue); // Send the doubled value back to the master
}Debug Message
Not Applicable
Other Steps to Reproduce
No response
I have checked existing issues, online documentation and the Troubleshooting Guide
- I confirm I have checked existing issues, online documentation and Troubleshooting guide.