刚开始学习树莓派，在使用I2C接口时遇到了一些问题，比如不了解smbus有那些函数和这些函数的使用方法，网上找了很久也没有找到具体说明smbus函数的文档，现将我整理的一些说明资料归档如下，一方面便于自己后期学习，二方面便于刚接触树莓派，想要更深入学习I2C接口功能的朋友们，希望对大家有所帮助：
使用方法：
首先在程序中导入“smbus”模块，方法如下：
#导入方法一：
import smbus
#导入方法二：
from smbus import SMBus
#创建一个smbus实例
b = smbus.SMBus(1)
b = SMBus(1) # 0 代表 /dev/i2c-0， 1 代表 /dev/i2c-1
#具体看使用的树莓派那个I2C来决定。
#实例创建好了就可以使用i2c函数了
b.read_byte_data(0x2f,0x58)
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function |
description |
parameters |
return value |
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|
SMBus Access |
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write_quick (addr) |
Quick transaction. |
int addr |
long |
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|
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 |
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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 |
|
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block_process_call (addr, cmd, vals) |
Block Process Call transaction. |
int addr, char cmd, long [ ] |
long [ ] |
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|
I2C Access |
||||
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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 |
|
函数介绍：
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)
