PCF8591组件（A/D和D/A转换）

PCF8591.h

#ifndef _PCF8591_H
#define _PCF8591_H

uint8_t getADCvalue(uint8_t chn);
void uint8_tToArray(uint8_t * arry, uint8_t val);

#endif

PCF8591.c

#include       //检查是否有误
#include "stdint.h"
#include "I2C.h"        //需要用到I2C通信协议
#include "PCF8591.h"

/* 读取当前的ADC转换值，chn-ADC通道号0~3 */
uint8_t getADCvalue(uint8_t chn) {
    uint8_t val;

    I2Cstart();
    if (I2Cwrite(0x48 << 1) == 0) {	//寻址PCF8591，如未应答，则停止操作并返回0
        I2Cstop();
        return 0;
    }
    I2Cwrite(0x40 | chn);	//写入控制字节，选择转换通道
    I2Cstart();
    I2Cwrite((0x48 << 1) | 0x01);  //寻址PCF8591，指定后续为读操作
    I2CreadAck();              //先空读一个字节，提供采样转换时间
    val = I2CreadNak();        //读取刚刚转换完的值
    I2Cstop();

    return val;
}
/* ADC转换值转为实际电压值的BCD码形式，arry-数组指针，val-AD转换值 */
void uint8_tToArray(uint8_t * arry, uint8_t val) {
	arry[0] = (uint8_t)((uint16_t)val * 25 / 2550);		//10^0
	arry[1] = (uint8_t)((uint16_t)val * 25 / 255) % 10;	//10^-1		
	arry[2] = (uint8_t)((uint16_t)val * 250 / 255) % 10;//10^-2
}