i2cset：向i2c設備某個寄存器寫入值

Usage: i2cset [-f] [-y] [-m MASK] [-r] [-a] I2CBUS CHIP-ADDRESS DATA-ADDRESS [VALUE] ... [MODE]
  I2CBUS is an integer or an I2C bus name
  ADDRESS is an integer (0x03 - 0x77, or 0x00 - 0x7f if -a is given)
  MODE is one of:
    c (byte, no value)
    b (byte data, default)
    w (word data)
    i (I2C block data)
    s (SMBus block data)
    Append p for SMBus PEC
    
    f:強制訪問
    y:指令執行自動yes，否則會提示確認執行Continue? [Y/n] Y，不加參數y會有很多執行提示，可以幫助判斷
    r:寫入后立即回讀寄存器的值，并將結果與寫入的值進行比較
    i2cbus：總線編號
    chip-address:i2c設備地址
    data-address:i2c寄存器地址
    value 要寫入的值
    mode：指定讀取的大小，b字節，w字，s是SMBus塊，i是i2c塊

設置i2c-1上0x20器件的0x77寄存器值為0x3f
./i2cset -f -y 1 0x20 0x77 0x3f

i2cget：讀取i2c設備某個寄存器的值

Usage: i2cget [-f] [-y] [-a] I2CBUS CHIP-ADDRESS [DATA-ADDRESS [MODE]]
  I2CBUS is an integer or an I2C bus name
  ADDRESS is an integer (0x03 - 0x77, or 0x00 - 0x7f if -a is given)
  MODE is one of:
    b (read byte data, default)
    w (read word data)
    c (write byte/read byte)
    Append p for SMBus PEC
    
    f:強制訪問
    y:關閉交互模式，不會提示警告信息
    i2cbus:總線編號
    chip-address:i2c設備地址
    data-address:i2c寄存器地址
    mode:指定讀取的大小，b字節，w字，s是SMBus塊，i是i2c塊

讀取i2c-1上0x20器件的0x77寄存器值
./i2cget -f -y 1 0x20 0x77

i2cdump：讀取某個i2c設備所有寄存器的值

Usage: i2cdump [-f] [-y] [-r first-last] [-a] I2CBUS ADDRESS [MODE [BANK [BANKREG]]]
  I2CBUS is an integer or an I2C bus name
  ADDRESS is an integer (0x03 - 0x77, or 0x00 - 0x7f if -a is given)
  MODE is one of:
    b (byte, default)
    w (word)
    W (word on even register addresses)
    s (SMBus block)
    i (I2C block)
    c (consecutive byte)
    Append p for SMBus PEC
    
    r:指定寄存器范圍，只能掃描從 first 到 last 區域
    f:強制訪問設備
    y:關閉人機交互模式
    i2cbus:總線編號
    address:指定設備地址
    mode:指定讀取的大小，b字節，w字，s是SMBus塊，i是i2c塊

讀取i2c1上0x38器件的所有寄存器
./i2cdump -f -y -a 1 0x38

一般寄存器都是8位地址的，i2cdump、i2cget、i2cset 也是設置讀取8位的地址，如果一次超過8位，需要用 i2ctransfer。

i2ctransfer：一次性讀寫多個字節

Usage: i2ctransfer [-f] [-y] [-v] [-V] [-a] I2CBUS DESC [DATA] [DESC [DATA]]...
  I2CBUS is an integer or an I2C bus name
  DESC describes the transfer in the form: {r|w}LENGTH[@address]
    1) read/write-flag 2) LENGTH (range 0-65535) 3) I2C address (use last one if omitted)
  DATA are LENGTH bytes for a write message. They can be shortened by a suffix:
    = (keep value constant until LENGTH)
    + (increase value by 1 until LENGTH)
    - (decrease value by 1 until LENGTH)
    p (use pseudo random generator until LENGTH with value as seed)

查看系統上存在的 i2c 總線及其設備地址

ls /sys/bus/i2c/devices/

可以在這里查看實際的設備，然后對比 i2c-tools 掃描出來的對不對。