剛開始學習樹莓派，在使用I2C接口時遇到了一些問題，比如不了解smbus有那些函數和這些函數的使用方法，網上找了很久也沒有找到具體說明smbus函數的文檔，現將我整理的一些說明資料歸檔如下，一方面便于自己后期學習，二方面便于剛接觸樹莓派，想要更深入學習I2C接口功能的朋友們，希望對大家有所幫助：

? ? ?? 使用方法：

首先在程序中導入“smbus”模塊，方法如下：

            
              #導入方法一：
import smbus

#導入方法二：
from smbus import SMBus

#創建一個smbus實例
b = smbus.SMBus(1)

b = SMBus(1)    # 0 代表 /dev/i2c-0， 1 代表 /dev/i2c-1
                #具體看使用的樹莓派那個I2C來決定。

#實例創建好了就可以使用i2c函數了
b.read_byte_data(0x2f,0x58)

            
          

?

?	function	description	parameters	return value
?	? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? SMBus Access
?	write_quick (addr)	Quick transaction.	int addr	long
?	read_byte (addr)	Read Byte transaction.	int addr	long
?	write_byte (addr, val)	Write Byte transaction.	int addr, char val	long
?	read_byte_data (addr, cmd)	Read Byte Data transaction.	int addr, char cmd	long
?	write_byte_data (addr, cmd, val)	Write Byte Data transaction.	int addr, char cmd, char val	long
?	read_word_data (addr, cmd)	Read Word Data transaction.	int addr, char cmd	long
?	write_word_data (addr, cmd, val)	Write Word Data transaction.	int addr, char cmd, int val	long
?	process_call (addr, cmd, val)	Process Call transaction.	int addr, char cmd, int val	long
?	read_block_data (addr, cmd)	Read Block Data transaction.	int addr, char cmd	long [ ]
?	write_block_data (addr, cmd, vals)	Write Block Data transaction.	int addr, char cmd, long [ ]	None
?	block_process_call (addr, cmd, vals)	Block Process Call transaction.	int addr, char cmd, long [ ]	long [ ]
?	? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I2C Access
?	read_i2c_block_data (addr, cmd)	Block Read transaction.	int addr, char cmd	long [ ]
?	write_i2c_block_data (addr, cmd, vals)	Block Write transaction.	int addr, char cmd, long [ ]	None

函數介紹：

Checking For Connected Devices

At the command prompt type one of these depending on whether you are using the I2C0 or I2C1 port:?

            
              sudo i2cdetect -y 0
//or
sudo i2cdetect -y 1

            
          

The 7 bit I2C address of all found devices will be shown (ignoring the R/W bit, so I2C address 0000 0110 is displayed as hex?03).

SMBus (System Management Bus) is a subset from the I2C protocol
When writing a driver for an I2C device try to use the SMBus commands if possible (if the device uses only that subset of the I2C protocol) as it makes it possible to use the device driver on both SMBus adapters and I2C adapters.

Note address is the 7 bit address?excluding the read / write bit (it will be shifted left 1 bit when added to the read/write bit)

            
              # Send only the read / write bit 
long write_quick(int addr)

# Read a single byte from a device, without specifying a device register. 
long read_byte(int addr)

# Send a single byte to a device 
long write_byte(int addr, char val)

# Read Byte Data transaction. 
long read_byte_data(int addr, char cmd)

# Write Byte Data transaction. 
long write_byte_data(int addr, char cmd, char val)

# Read Word Data transaction. 
long read_word_data(int addr, char cmd)

# Write Word Data transaction. 
long write_word_data(int addr, char cmd, int val)

# Process Call transaction. 
long process_call(int addr, char cmd, int val)

#Read Block Data transaction.  
long[] read_block_data(int addr, char cmd)
    
# Write up to 32 bytes to a device.  This fucntion adds an initial byte indicating the 
# length of the vals array before the valls array.  Use write_i2c_block_data instead! 
write_block_data(int addr,char cmd,long vals[])

# Block Process Call transaction.  
long[] block_process_call(int addr, char cmd, long vals[])
 
   
# I2C Access Functions
# Block Read transaction. 
long[] read_i2c_block_data(int addr, char cmd)

#Block Write transaction. 
write_i2c_block_data(int addr, char cmd, long vals[])


#Code Example

#!/usr/bin/python

import smbus

bus = smbus.SMBus(1)    # 0 = /dev/i2c-0 (port I2C0), 1 = /dev/i2c-1 (port I2C1)

DEVICE_ADDRESS = 0x15      #7 bit address (will be left shifted to add the read write bit)
DEVICE_REG_MODE1 = 0x00
DEVICE_REG_LEDOUT0 = 0x1d

#Write a single register
bus.write_byte_data(DEVICE_ADDRESS, DEVICE_REG_MODE1, 0x80)

#Write an array of registers
ledout_values = [0xff, 0xff, 0xff, 0xff, 0xff, 0xff]
bus.write_i2c_block_data(DEVICE_ADDRESS, DEVICE_REG_LEDOUT0, ledout_values)

            
          

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