Jetson Nano I2C相关调试总结

写在前面，Jetson Nano关于I2C没有对C语言的支持，使用编程语言是python。因为I2C涉及寄存器部分设置，在没有硬件的指导手册情况下，新手向不是很友好。现有可直接使用的库都是python，如果需要使用C或者C++，可参考libi2c（https://github.com/amaork/libi2c ）或者libgpiod（https://github.com/brgl/libgpiod ）。

参考文章

• https://www.jetsonhacks.com/2019/07/22/jetson-nano-using-i2c/
• https://www.jianshu.com/p/f60b6a2fd736
• https://blog.csdn.net/thystar/article/details/53021992
• https://blog.csdn.net/qq_15807167/article/details/53435831
• https://www.ncnynl.com/archives/201704/1526.html

I2Ctool检查命令：i2cdetect/i2cdump/ i2cset/i2cget

I2Ctool安装

$ sudo apt-get update
$ sudo apt-get install -y i2c-tools

检查安装情况

$ apt-cache policy i2c-tools

输出如下即为安装成功

i2c-tools:
已安装：4.0-2
候选： 4.0-2
版本列表：
*** 4.0-2 500
500 http://ports.ubuntu.com/ubuntu-ports bionic/universe arm64 Packages
100 /var/lib/dpkg/status

i2cdetect

1. 列出安装的所有总线

命令

 $ sudo i2cdetect -l

效果

i2c-3 i2c 7000c700.i2c I2C adapter
i2c-1 i2c 7000c400.i2c I2C adapter
i2c-6 i2c Tegra I2C adapter I2C adapter
i2c-4 i2c 7000d000.i2c I2C adapter
i2c-2 i2c 7000c500.i2c I2C adapter
i2c-0 i2c 7000c000.i2c I2C adapter
i2c-5 i2c 7000d100.i2c I2C adapter

2. 扫描某一总线bus上所有i2c设备，并且打印出设备i2c总线地址

命令（其中1为i2c设备号）

 $ sudo i2cdetect -y -r -a 1

参数: -y是无视交互问题直接执行，-r是SMBus read byte命令，-a是所有地址，1是指i2c-1。

效果

      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- 77  

其中，0x68和0x77 为i2c设备在I2C_1上的总线地址

i2cdump

作用是寄存器数据导出。总线上i2c设备的数据是要存储在寄存器上。
命令

sudo i2cdump -y 1 0x68

含义为：导出I2C-1中地址为0x68的设备的数据
效果，左边是寄存器地址，右侧数据

 No size specified (using byte-data access)
           0   1    2   3   4    5    6   7    8   9    a   b    c   d   e   f    0123456789abcdef
 00: 0a 51 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ?Q..............
 10: 00 08 00 00 57 00 00 00 00 00 00 00 00 00 00 00    .?..W...........
 20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 50: 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00    ....?...........
 60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 20    ............... 
 80: 0a 51 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ?Q..............
 90: 00 08 00 00 57 00 00 00 00 00 00 00 00 00 00 00    .?..W...........
 a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 d0: 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00    ....?...........
 e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 20    ............... 

i2cset
寄存器数据写入，即向寄存器中某一位地址上插入数据：
命令(sudo i2cset -y 1 i2c设备地址 写入位置 写入内容)

sudo i2cset -y 1 0x68 0x20 0x55

效果,(寄存器地址0x20上被插入数据0x55)

 No size specified (using byte-data access)
           0   1    2   3   4    5    6   7    8   9    a   b    c   d   e   f    0123456789abcdef
 00: 0a 51 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ?Q..............
 10: 00 08 00 00 57 00 00 00 00 00 00 00 00 00 00 00    .?..W...........
 20: 55 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 50: 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00    ....?...........
 60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 20    ............... 
 80: 0a 51 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ?Q..............
 90: 00 08 00 00 57 00 00 00 00 00 00 00 00 00 00 00    .?..W...........
 a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 d0: 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00    ....?...........
 e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 20    ............... 

i2cget

读出总线地址为0x77设备的0x90寄存器地址的数据

命令（sudo i2cget -y 1 i2c设备地址 寄存器位置）

sudo i2cget -y 1 0x68 0x80

效果

0x0a

Jetson Nano I2C设备

如图是jetson nano的i2c所有设备，共7组。
具体实例可以参考文章 https://www.jianshu.com/p/f60b6a2fd736
其中有几项需要说明

1. i2c设备需要安装相应的库（主要是用来设置该设备的接口和寄存器地址等，或者部分功能输出函数），如果未安装适合该设备的库，可以在网址 https://pypi.org/ 中输入设备名称寻找并安装。
2. 安装后可能需要修改部分库以适配当前的开发环境，例如修改设备总线地址等。库的安装路径为

/usr/local/lib/python3.6/dist-packages

可在其中寻找安装好的库，修改 ini.py文件。