int8_t I2C_write(uint8_t addr, uint8_t reg_addr, const uint8_t* data, uint8_t len)  // packet function
{
    HAL_StatusTypeDef  status =HAL_OK;
. J$ ]9 Y/ |; O3 N    uint16_t deviceWriteAddr = (addr << 1);    //7 bit write address shall be pre-processed
    status = HAL_I2C_Mem_Write(&hi2c1,deviceWriteAddr,(uint16_t)reg_addr,1,(uint8_t*)data,(uint16_t)len,I2C_READ_TIMEOUT);
    if (HAL_OK != status)
! E3 K# H! h' m/ f9 S$ N    {
        printf("I2C Write Fail:%d\n\r",status);
        return status;
4 L6 I3 L( ?! E  s    }
    return HAL_OK;
}
# l$ e9 t# y: E5 W, x1 _2 t6 b
5 V  F- w7 E# ?& } int8_t I2C_read(uint8_t addr, uint8_t reg_addr, const uint8_t* data, uint8_t len)  //re packet function
" ?5 C8 c0 ]& n, O" }4 Q2 L{
% N- Z( S8 f, u! \1 T; J    HAL_StatusTypeDef  status =HAL_OK;
" ]% `, S5 F& }: w   uint16_t deviceWriteAddr = addr << 1; //7 bit write address shall be pre-processed
: s0 W* O$ L* E0 D4 \      uint16_t deviceReadAddr = (addr << 1)|0x01;   //7 bit read address shall be pre-processed   
$ e/ M0 V1 F( Q3 ?   uint8_t regAddr = reg_addr;
         
9 r3 r) B7 s; _2 t( s8 f. j8 a8 s status = HAL_I2C_Master_Transmit(&hi2c1,deviceWriteAddr,&regAddr,1,I2C_READ_TIMEOUT);
   
if (HAL_OK != status)
6 Z# [5 ~# I  g6 O+ R* s7 [    {
        printf("I2C readreg Fail:%d\n\r",status);
1 H+ P  ~% K0 O2 G/ J: A3 J# r8 b        return status;
    }   

    status = HAL_I2C_Master_Receive(&hi2c1,deviceReadAddr,(uint8_t*)data,(uint16_t)len,I2C_READ_TIMEOUT); //
; O0 b1 ]; {7 S# e7 z    if (HAL_OK != status)
    {
        printf("I2C Read1 Fail:%d\n\r",status);
        return status;
+ w- d0 v' W5 X% r/ }5 R! M    }
    return HAL_OK;
}
" _! e! z# _8 [8 p
% V2 X5 p3 k( q3 O# {# v写是用HAL_I2C_Mem_Write（) 重新打包；
读操作原本要用HAL_I2C_Mem_Read，发现多字节request时，返回 I2C error.
+ T9 x9 \% `+ q, \如上改过后，单字节，多字节 读写稳定。
7 z" r4 d% `( Y7 ^HAL_I2C_Mem_Write/HAL_I2C_Mem_Read 都是cubeMX 工具生成的HAL库。
我是在STM32L4系列使用的。
: C9 K  o: R7 g2 S. X0 z" }我参考的I2C 协议参考：http://www.cnblogs.com/aaronLinux/p/6218660.html