This is my I2C packet, and I am not understanding how to send data to my slave

Using Arduino Programming Questions
1

Click the above to check the I2C packet structure. I am not getting any response from the slave. This is my master code.

I am writing to the slave and requesting for every 100 ms, and there is no response form the slave device. help me.

#include <Wire.h>
#include <TimerOne.h> // Header file for TimerOne library

//#ifndef TWI_FREQ
//#define TWI_FREQ 100000L
//#endif

#define LED0 13 // Pin 3
#define TIMER_US 100000 // 100mS set timer duration in microseconds

char send_data[8] = {'F','F','F','F','F','F','F','F'}; //dummy initial values
char receive_data[8] = {'1','1','1','1','1','1','1','1'}; //dummy initial values

int message_flag = 0;

void setup()
{
pinMode(LED0, OUTPUT); // Set the pins as outputs
Timer1.initialize(TIMER_US); // Initialise timer 1
Wire.begin();
Wire.setClock(100000);
Serial.begin(9600);
}

void loop()
{
Timer1.attachInterrupt( timerIsr ); // attach the ISR routine here

if(message_flag == 1)
{
Wire.beginTransmission(0x20); // transmit to device #8
Serial.println("Arduino to HMI");
// for(int i=0; i<8; i++)
// {
// Wire.write(send_data*); // sends five bytes*
// Serial.print(send_data*);
_// }_
_ Wire.write(0x40);_
_ Wire.write(0x00);_
_ Wire.write(0x00);_
_ Wire.write(0x00);_
_ Wire.write(0x41);*_

* Serial.println(" ");*
* Wire.endTransmission(); // stop transmitting*

* Wire.requestFrom(0x20, 8);*
* while(Wire.available() > 1)*
* {*
* Serial.println("HMI to Arduino");*
* for(int j =0; j<8; j++)*
* {*
* receive_data[j] = Wire.read();
Serial.print(receive_data[j]);
_ }_
_ Serial.println("");_
_ }_
message_flag = 0;
_ }_
_}_
void timerIsr()
_{_
_ digitalWrite( LED0, digitalRead( LED0 ) ^ 1 ); // Toggle LED 0*_
* message_flag = 1;
_}*_

2

I think it's about time to get used to using code tags, don't you?

3

what is the slave? please share the datasheet if possible

4

Thanks for that Awol,

Lets do this,

Here is the code:

#include <Wire.h> //includes I2C library
#include <TimerOne.h> // Header file for TimerOne library to generate timer interrupt

#ifndef TWI_FREQ //code to set 100KHZ
#define TWI_FREQ 100000L
#endif

#define LED0 13 // Pin 3
#define TIMER_US 100000 // 100mS set timer duration in microseconds

char send_data[8] = {'F','F','F','F','F','F','F','F'}; //dummy initial values
char receive_data; //dummy initial values

int message_flag = 0;

void setup()
{
pinMode(LED0, OUTPUT); // Set the pins as outputs
Timer1.initialize(TIMER_US); // Initialise timer 1
Wire.begin();
Wire.setClock(100000);
Serial.begin(9600);
}

void loop()
{
Timer1.attachInterrupt( timerIsr ); // attach the ISR routine here

if(message_flag == 1)
{
Wire.beginTransmission(0x20); // transmit to device #2
Serial.println("Arduino to HMI");

Wire.write(0x40); //send data 1
Wire.write(0x00); //send data 2
Wire.write(0x00); //send data 3

Serial.println(" ");
Wire.endTransmission(); // stop transmitting

Wire.requestFrom(0x20, 1); //requesting 1 byte of data from 20 slave
while(Wire.available() > 1)
{
Serial.println("HMI to Arduino");

receive_data = Wire.read(); //reading
Serial.print(receive_data); //print in serial

Serial.println("");
}
message_flag = 0; // flag to run for every 100 milli seconds
}
}

void timerIsr()
{
digitalWrite( LED0, digitalRead( LED0 ) ^ 1 ); // Toggle LED 0
message_flag = 1; // flag to run for every 100 milli seconds
}

5

Please see reply #1

6

oops..!! still you need some more code tags to understand the code ? :frowning:

7

britto:
oops..!! still you need some more code tags to understand the code ? :frowning:

Why can't you just do as requested?

8

code:

#include <Wire.h> // included i2c library
byte data_1 = 0x02; // first dummy data byte stored in an variable to pass to HMI
byte data_2 = 0x00; // second data byte (not used for testing now)
byte data_3 = 0x00; // third data byte (not used for testing now)
byte message_1; // Variable to receive first byte
byte message_2; // Variable to receive second byte
byte value_1; // acknowleding the status of transmission

void setup() {
Wire.begin(); // beginning the i2c transmission
Serial.begin(9600); // beginning serial for display
}

void loop(){
Wire.beginTransmission(0x20); // begin to transmit to device 0x20
Wire.write(data_1); // sends one byte
Wire.write(data_2); // second byte transmission, not under test now
Wire.write(data_3); // third byte transmission, not under test now
value_1 = Wire.endTransmission(); // stop transmitting & return the acknowledgement
Serial.println(value_1); // printing the transmission status in serial display

Wire.requestFrom(0x20, 2); // request 2 bytes from slave device #8
while (Wire.available()) { // read the bytes in the data pin. if any
message_1 = Wire.read(); // reading first byte
message_2 = Wire.read(); // reading second byte
Serial.println(message_1); // print the readed messages
Serial.println(message_2); // print the readed messages
}
}

while, writing to slave device, this code works fine. when I try to request data byte from slave, the communication is getting interrupted. Help me to solve this issue.

9

your problem could be here (THIS IS WHAT USING CODE TAG MEANS BTW):

  while (Wire.available()) {                            // read the bytes in the data pin. if any
    message_1 = Wire.read();                            // reading first byte
    message_2 = Wire.read();                            // reading second byte
    Serial.println(message_1);                          // print the readed messages
    Serial.println(message_2);                          // print the readed messages
  }

did you try doing this instead?

  while (Wire.available()) {                      // output all bytes received to serial monitor
    Serial.println(Wire.read());                          // print the readed messages
  }