Man-Machine Interfaces

Inter-Integrated Circuit

Content

Conpect

Function	I2C	SMBus
Clock	SLC (Serial clock line)	SMBCLK
Data	SDA (Serial data line)	SMBDAT

Requirements

BeagleBone Black

Precondition

# apt-get install libi2c-dev
# apt-get install i2c-tools
# apt-get install python-smbus

Programming

Shell

CLI	Description
i2cdetect	i2c device detects
i2cdump	Dump register value
i2cget	Read register value
i2cset	Write register

i2cdetect -l

i2c-1 i2c OMAP I2C adapter I2C adapter i2c-2 i2c OMAP I2C adapter I2C adapter #<= Cap i2c-0 i2c OMAP I2C adapter I2C adapter #<= Internal

i2cdetect -y -r 0

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

00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: UU -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- #<= EEPROM, accessing by 24c256 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- --

i2cdetect -y -r 2

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

00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- #<= Cap 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- --

-

# i2cset -y 0 0x20 0x12 0x00

Reading Serial number from EEPROM of BBG (offset 4 byte then hexdump 24 byte)

# hexdump -e '8/1 "%c"' /sys/bus/i2c/devices/0-0050/eeprom -s 4 -n 24
A335BNLTBBG1BBG216113134

cat /sys/bus/i2c/devices/0-0050/modalias

i2c:24c256

dmesg | grep 24c

[ 1.527894] at24 2-0054: 32768 byte 24c256 EEPROM, writable, 1 bytes/write [ 1.528408] at24 2-0055: 32768 byte 24c256 EEPROM, writable, 1 bytes/write [ 1.528654] at24 2-0056: 32768 byte 24c256 EEPROM, writable, 1 bytes/write [ 1.528866] at24 2-0057: 32768 byte 24c256 EEPROM, writable, 1 bytes/write [ 1.943267] at24 0-0050: 32768 byte 24c256 EEPROM, writable, 1 bytes/write

cat /proc/kallsyms | grep at24

c08fb370 t at24_remove c08fb3c4 t at24_write c08fb468 t at24_read c08fb514 t at24_eeprom_write_i2c c08fb6cc t at24_eeprom_write_smbus_byte c08fb7e0 t at24_eeprom_write_smbus_block c08fb928 t at24_eeprom_read_i2c c08fbad4 t at24_eeprom_read_mac c08fbbf4 t at24_eeprom_read_serial c08fbd2c t at24_eeprom_read_smbus c08fbe58 t at24_probe c0d86410 r at24_ids c13556c8 t at24_init c136dbe8 t at24_exit c13bedec t __initcall_at24_init6 c14b5808 d at24_driver

C

C Function List

Function	User Space (SMBus)	Kernel Space
HEADER File	`i2c.h` `i2c-dev.h`
START Condition		i2c_start()
STOP Condition		i2c_stop()
Read	i2c_smbus_read_byte_data	sendbytes()
Write	i2c_smbus_write_word_data	readbytes()

Case

Reading Serial number from EEPROM of BBG

Monitor the CPU temperature of IPC

# apt-get install lm-sensors 
# sensors-detect