Raspberry pi with Arduino using i2c

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Posted by: @mohamedmym

Hi,

I'm trying to connect raspberry pi with Arduino using I2C communication protocol, But I'm have a problem.

when I'm trying to write data to Arduino (as it's the slave device) from the pi (the master device),

the data arrives perfectly.

but when I'm trying to read data from the Arduino I always get 0.

here's my code plz some one help me.

//Arduino Code:

#include <Wire.h>
int dataSize;
char data[32];
char response[32];
char Buffer[80];
String answer = "Hi from Arduino";

void setup() {
    pinMode(13, OUTPUT);
    digitalWrite(13, 0);
    Serial.begin(9600);
    Wire.begin(0x8);

    Wire.onReceive(receiveEvent);
    Wire.onRequest(requestEvent);
    delay(500);
    Serial.println("Welcome To I2c test.");
    for (byte i = 0; i < 32; i++) {
        data[i] = 0x00;
    }
    for (byte i = 0; i < 32; i++) {
        response[i] = 0x00;
    }

}

void loop() {
    if (Serial.available()) {
        answer = Serial.readString();
    }
    delay(10);
}

int counter = 0;
char x;

void receiveEvent(int howMany) {
    dataSize = Wire.read();

 

    while (Wire.available()) {
        x = Wire.read();
        data[counter] = x;
        counter++;
    }

    Serial.print("Data Size: ");
    Serial.println(dataSize);
    Serial.print("Data Received: ");
    Serial.println(data[0]);
    Serial.println(data);
    counter = 0;

    for (int i = 0; i < 30; i++)
        data[i] = 0;
    }

    void requestEvent(){

    char response[32];

    if (sizeof(answer) < 32) {
        for (byte i = 0; i < 32; i++) {
            if (answer.charAt(i) != 0)
                response[i] = answer.charAt(i);
            else
                response[i] = 0xff;
        }
    }    

    dataSize = Wire.read();
    Wire.write(response);
    sprintf(Buffer, "Data: \n[%03d,%03d,%03d,%03d,\t%03d,%03d,%03d,%03d,\n %03d,%03d,%03d,%03d,\t%03d,%03d,%03d,%03d,\n %03d,%03d,%03d,%03d,\t%03d,%03d,%03d,%03d,\n %03d,%03d,%03d,%03d,\t%03d,%03d,%03d,%03d]"
, response[0], response[1], response[2], response[3], response[4], response[5], response[6], response[7]
, response[8], response[9], response[10], response[11], response[12], response[13], response[14], response[15]
, response[16], response[17], response[18], response[19], response[20], response[21], response[22], response[23]
, response[24], response[25], response[26], response[27], response[28], response[29], response[30], response[31]);

    Serial.println("Request Event");
    Serial .println(Buffer);

    for (byte i = 0; i < 32; i++) {
        response[i] = 0xff;
    }
    for (byte i = 0; i < 32; i++) {
        data[i] = 0xff;
    }

}

 

/***************************************************/

#Raspberry Pi Code (Python):

from smbus import SMBus
import time
name = "Welcome to my test"

data = []
bus = SMBus(1)

time.sleep(0.5)
data1 = 48
for i in name:
    data.append(i)

for i in range(len(data)):
    try:
        data [i] = ord(data[i])
    except:
        data[i] = 0

time.sleep(0.1)
print (data)

print(len(data), "Bytes")
bus.write_byte_data(0x8,len(data),data1+2)
print ("data sent")
time.sleep(1)

rec = bus.read_i2c_block_data(0x8,32,32);
print(rec)

##################################

I've tried the read_i2c_block_data () function, and the read_byte_data() function but still the same.