adxl312_i2cLib

This Library can be used to communicate with the I2C protocol for the ADXL312 Digital Accelerometer in Embedded Linux Systems.

You can find detailed definitions of ADXL312 in the adxl312_io.h library.

• Setup
• Write Byte
• Write Bytes
• Read Byte
• Read Bytes
• Close

Setup

i2c_init function takes 2 parameters. They are \*i2cdevice and addr. This function open device and talk with i2c slave. If connection has any error return -1. If connection is Ok than return opened file data.

int i2c_init(char *i2cdevice,int addr){
	int file;
	if( ( file = open(i2cdevice,O_RDWR)) < 0 ){
		perror("Failed to open the i2c bus\n");
		return -1;
	}
	if( ioctl(file,I2C_SLAVE,addr) < 0 ) {
		printf("Failed to talk i2c\n");
		return -1;
	}
	return file;
}

Write Byte

i2c_writeByte function takes 3 parameters. They are file,addr and value. file is opened device and addr is the address to be written and value is the value to send. This function returns 1 if write correctly else return -1.

int i2c_writeByte(int file,int addr,int value){
	char buf[10] = {0};
	buf[0] = addr;
	buf[1] = value;
	if(write(file,buf,2) != 2){
		printf("Error setting i2c device\n");
		return -1;
	}
	return 1;
}

Write Bytes

i2c_writeBytes function takes 4 parameters. They are file,addr, value[] and nbytes. file is opened device and addr is the address to be written, value[] is the array values to send and nbytes shows how many bytes are written. This function returns 1 if write correctly else return -1.

int i2c_writeBytes(int file,int addr,char value[10],int nbytes){
	int i;
	unsigned char buf[10] = {0};
	buf[0] = addr ;
	for(i=0;i<nbytes;i++)
		buf[1+i] = value[i];
	if(write(file,buf,nbytes) != nbytes){
		printf("Error writing bytes to i2c device\n");
		return -1;
	}
	return 1;
}

Read Byte

i2c_readByte function takes 2 parameters and its returning type is a char. file is opened device and addr is a address to be read. This function returns the byte value read from the address if read is successful, otherwise returns -1.

char i2c_readByte(int file,int addr){

	char buf = addr;
	if(write(file,&buf,1) != 1 ){
		printf("Error reading byte from i2c device\n");
		return -1;
	}
	buf = '\0';
	if(read(file,&buf,1)!=1){
		printf("Error reading byte from i2c device\n");
		return -1;
	}
	return buf;
}

This function takes 4 parameters. It reads more than one address from device. This function freturns 16 bit byte value read from the address if read is successful, otherwise return -1.

int i2c_readByte(int file,int addr1,int addr2){

	char buf1,buf2;
	int fl = 0x0000FFFF;
	if(write(file,&addr1,1) != 1 ){
		printf("Error reading byte from i2c device\n");
		return -1;
	}
	if(read(file,&buf1,1)!=1){
		printf("Error reading byte from i2c device\n");
		return -1;
	}
	if(write(file,&addr2,1) != 1 ){
		printf("Error reading byte from i2c device\n");
		return -1;
	}
	if(read(file,&buf2,1)!=1){
		printf("Error reading byte from i2c device\n");
		return -1;
	}
	printf(":::  0x%02x  ::: 0x%02x \n",buf1,buf2);
	int bf = ((int)buf1 << 8) | buf2;
	return (fl&bf);
}

Read Bytes

*i2c_readBytes function takes 3 parameters and its returning type is a char*. file is opened device, addr is a address to be read and nbytesshows how many bytes are read. This function returns the byte array value read from the address if read is successful, otherwise returns NULL.

char *i2c_readBytes(int file,int addr,int nbytes){
	char *bufx;
	if( ( bufx = (char*)calloc(nbytes,sizeof(char)) ) == NULL ){
		printf("Error allocating buffer...\n");
		return NULL;
	}
	char buf = addr;
	if(write(file,&buf,1) != 1 ){
		printf("Error reading bytes from i2c device\n");
		return NULL;
	}
	if(read(file,bufx,nbytes) != nbytes){
		printf("Error reading byte from i2c device\n");
		return NULL;
	}
	return bufx;
}

Close

Close opened file function.

int i2c_close(int file){
	if(close(file)!=0){
		printf("Error while closing file...\n");
		return -1;
	}
	return 1;
}