Main.c
#include "ads1118.h"
void Init(void)    //此函数方便串口调试
{
  TMOD = 0X20;
  TH1 = 0XF3;
  TL1 = 0XF3;
  TR1 = 1;
  SM1 = 1;SM0 = 0;
  REN = 1;
  TI = 1;
}
float Volt_Value;
void main(void)单片机printf函数
{
    uint value;
    Init();
    EA = 1;
    ADS1118_Init();
    Write_ADS1118(CONFIG_VALUE,0);
    while(1)
    {
        delay_ms(1000);
        value  =  ADS_SEL_Read(0,4);  //0.512V
        printf("value = %d\n\r",value);
        Volt_Value = value*0.512/32768;  //第二次转换时读出的是前一次的电压
        printf("Volt_Value %f\n\r\n\r",Volt_Value);
  }
}
Ads1118.c
#include "ads1118.h"
void delay_ms(uint z)
{
    uint x;
    for(;z>0;z--)
    for(x=120;x>0;x--);
}
void ADS1118_Init(void)
{
    CS_H;
    SCLK_H;
    MOSI_L;
}
union aa
{
    uint dat1[2];
    ulong dat2;
};
uint Write_ADS1118(uint dat,uchar mode)
{
//    uint temp;
    union aa temp;
    union aa temp1;
//    ulong Value;
    uchar i;       
    if(mode == 1) dat |= 0x8000;   
    temp.dat1[1] = dat;
      temp.dat1[0] = dat;
    SCLK_L;
    CS_L;
    delay_ms(1);
    for(i=0;i<32;i++)
    {
        if(temp.dat2 & 0x80000000)MOSI_H;
        else MOSI_L;
        temp.dat2 <<= 1;
        _nop_();
        SCLK_H;
        _nop_();
        SCLK_L;
        _nop_();
       
        temp1.dat2 <<= 1;
        if(READ_MISO)temp1.dat2 |= 0x01;
        _nop_();
    }
      CS_H;
    SCLK_L;
    MOSI_L;
    MISO_L;
    printf("temp %d\n\r",temp1.dat1[0]);
    printf("temp %#X\n\r",temp1.dat1[1]);
    return temp1.dat1[0];
}
int ADS_SEL_Read(uchar road,uchar Ref)        //测几路电压
{
    int dat = 0;
    uint Config_Value = 0x008b;                    //默认低8位，DOUT带上拉电阻
    switch(road)
    {
    case 0:  Config_Value += 0x0000;break;    //AINP = AIN0 and AINN = AIN1 (default)
    case 1:  Config_Value += 0x1000;break;    //AINP = AIN0 and AINN = AIN3
    case 2:  Config_Value += 0x2000;break;    //AINP = AIN1 and AINN = AIN3
    case 3:  Config_Value += 0x3000;break;    //AINP = AIN2 and AINN = AIN3
    case 4:  Config_Value += 0x4000;break;    //AINP = AIN0 and AINN = GND
    case 5:  Config_Value += 0x5000;break;    //AINP = AIN1 and AINN = GND
    case 6:  Config_Value += 0x6000;break;    //AINP = AIN2 and AINN = GND
    case 7:  Config_Value += 0x7000;break;    //AINP = AIN3 and AINN = GND
    default : break;
    }
    switch(Ref)
    {
    case 0:  Config_Value += 0x0000;break;    //000 : FS = ±6.144V(1)
    case 1:  Config_Value += 0x0200;break;    //001 : FS = ±4.096V(1)
    case 2:  Config_Value += 0x0400;break;    //002 : FS = ±2.048V(1)
    case 3:  Config_Value += 0x0600;break;    //003 : FS = ±1.024V(1)
    case 4:  Config_Value += 0x0800;break;    //004 : FS = ±0.512V(1)
    case 5: case 6: case 7: Config_Value += 0x0a00;break;    //005 : FS = ±0.256V(1)
    default : break;
    }
    CS_L;
    dat = Write_ADS1118(Config_Value,1);
    _nop_();
    CS_H;
    return dat;
}
Ads1118.h
#include <reg52.h>
#include <stdio.h>
#include <intrins.h>
typedef unsigned char uchar;
typedef unsigned int  uint;
typedef unsigned long ulong;
#define CONFIG_VALUE    0X038B      //AIN0-AIN1  4.096  128sps  pull on DOUT
sbit SCLK = P2^1;
sbit MOSI = P2^2;
sbit MISO = P2^3;
sbit CS  = P2^0;
#define SCLK_H    SCLK = 1
#define SCLK_L    SCLK = 0
#define MOSI_H    MOSI = 1
#define MOSI_L    MOSI = 0
#define MISO_H    MISO = 1
#define MISO_L    MISO = 0
#define CS_H      CS = 1
#define CS_L      CS = 0
#define READ_MISO  P2 & 0X8 
void ADS1118_Init(void);
uint Write_ADS1118(uint dat,uchar mode);
void delay_ms(uint z);
int ADS_SEL_Read(uchar road,uchar Ref);