7

6

5

4

3

2

1

0

0

1

0

1

0

A2

A1

A0

$ i2cdetect -r 2 0x50 0x50

WARNING! This program can confuse your I2C bus, cause data loss and worse!

I will probe file /dev/i2c-2 using read byte commands.

I will probe address range 0x50-0x50.

Continue? [Y/n] Y

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f

00:                                                

10:                                                

20:                                                

30:                                                

40:                                                

50: 50                                             

60:                                                

70:   

$ i2cset -f -y 2 0x50 0x00 0x80

$ i2cget -y 2 0x50 0x00

0x80

$ i2cdetect -F 2

Functionalities implemented by /dev/i2c-2:

I2C                              yes

SMBus Quick Command              no

SMBus Send Byte                  yes

SMBus Receive Byte               yes

SMBus Write Byte                 yes

SMBus Read Byte                  yes

SMBus Write Word                 yes

SMBus Read Word                  yes

SMBus Process Call               yes

SMBus Block Write                yes

SMBus Block Read                 no

SMBus Block Process Call         no

SMBus PEC                        yes

I2C Block Write                  yes

I2C Block Read                   yes

I2C Read Write source code

Download Source Code

 Explanation

int main(void) {

int f,i=0,n=0;  char buf[10];

/* Open the adapter and set the address of the I2C device */

(1) f = open("/dev/i2c-2", O_RDWR);

/* Set the address of the i2c slave device */

(2) ioctl(f, I2C_SLAVE, I2C_ADDRESS) == -1)

/* write 9  bytes at 0x50*/

(3) buf[0] = 0x50;  // location is 0x50

(4) buf[1] = 0x30; // 0x30 is for location 0x50

  buf[2] = 0x31; // 0x31 is for location 0x51

  buf[3] = 0x32; // 0x32 is for location 0x52

  buf[4] = 0x33; // 0x33 is for location 0x53

  buf[5] = 0x34; // 0x34 is for location 0x54

  buf[6] = 0x35; // 0x35 is for location 0x55

  buf[7] = 0x36; // 0x36 is for location 0x56

  buf[8] = 0x37; // 0x37 is for location 0x57

  buf[9] = 0x38; // 0x38 is for location 0x58

(5)  n = write(f, buf, 10);

(1) – open I2C bus 2, in read write mode. File handle will be f. 

(2) - ioctl call, to set address of I2C device.

I2C_SLAVE is 0x0703 (pre-defined) 

refer “i2c-dev.h”

I2C_ADDRESS is 0x50.

(3) - buf [0] is getting starting location from where we want to write. We want to write to location 0x50 onwards.

(4) - buf [1] to buf [9] will get data, which will be written to location 0x50 to 0x58.

(5) – content of buffer will be written to f.

/* Set the 16-bit address to read*/

(6)buf[0] = 0x50; /* address byte 1 */

(7) n = write(f, buf,1);

(8)for (i=0;i<10;i++) buf[i]= 0;

//read 9 bytes from that address

(9)n = read(f, buf,9);

This portion of code is about reading from I2C EEPROM

(6)  and (7) – setting location from  where we want to read. We are reading from location 0x50.

(8) – clearing buffer

(9) – reading 9 bytes, because in (5) we have written from location 0x50 to 0x58, total 9 bytes.