I2C接口的输入与输出驱动的PCF8574-.doc

I2C接口的输入与输出驱动的PCF8574-pcf8574采用I2C接口，有8个准双向口，可以和外部电路连接，来实现输入输出功能，可以用来对口线进行扩展有几点需要注意1.某位作为输入的时候，必须首先置为高电平2.地址是0100 A2 A1 A0 R/W3.最多可以扩展8片4.低电流损耗，静态电流10uA,驱动电流比较大，而且有索存功能，能够驱动LED发光管5.带有外部中断输出，低电平有效我作了一个电路，其中P7-P4作为输入检测开关状态，P3-P0作为输出来驱动LED灯程序如下#include reg51.h#define SETBIT(VAR,Place) (VAR|=(1Place)#define CLRBIT(VAR,Place) (VAR&=(1Place)255)sbit IC_SCL=P36;sbit IC_SDA=P37;unsigned char IC_Re_Time;unsigned char IC_Err_Flag;void Timer0_Init(void)TMOD=0x00;/timer0工作定时器方式0，13位技术TH0=0x1e;/5msTL0=0x0c;/5msTR0=1;/启动时钟0ET0=1;/允许时钟0进行中断EA=1;/开放所有中断void Delay(void)unsigned char i;for(i=0;i=10;i+);unsigned char VALBIT(unsigned int Val,unsigned char Bit)unsigned int Buf;Buf=0x0001;if(Bit) Buf=Bit;Val&=Buf;if(Val) return(0xff);else return(0x00);/* 下面是PCF8574的操作程序1.通信方式:I2C2.通信端口:IC_SCL(P3.6),IC_SDA(P3.7)3.通信地址:0x0101000x*/void IC_Start(void)/启动IC通信IC_SDA=1;Delay();IC_SCL=1;Delay();IC_SDA=0;Delay();IC_SCL=0;Delay();void IC_Stop(void)/停止IC通信IC_SDA=0;Delay();IC_SCL=1;Delay();IC_SDA=1;Delay();void IC_Receive_Ack(void)/接受ACKIC_SDA=1;IC_SCL=1;Delay();IC_Re_Time=0;while(IC_Re_Time=30)if(IC_SDA=0)IC_Err_Flag=0;break;elseIC_Err_Flag=1;IC_SCL=0;Delay();/void IC_Send_ACK(void)/发送ACK/if read many datas at a time,this can be used/IC_SDA=0;/Delay();/IC_SCL=1;/Delay();/IC_SCL=0;/Delay();/IC_SDA=1;/void IC_Send_NAck(void)/发送NACKIC_SDA=1;Delay();IC_SCL=1;Delay();IC_SCL=0;Delay();void IC_Write_Byte(unsigned char Data)/写数据到8574unsigned char i;for(i=0;i=7;i+)if(VALBIT(Data,(7-i)/data out msbIC_SDA=1;elseIC_SDA=0;IC_SCL=1;Delay();IC_SCL=0;Delay();unsigned char IC_Read_Byte(void)/从8574读取一个数据unsigned char i;unsigned char Data;for(i=0;i=7;i+)IC_SCL=1;Delay();IC_SDA=1;Delay();if(IC_SDA)SETBIT(Data,(7-i);/data in msb tooelseCLRBIT(Data,(7-i);IC_SCL=0;Delay();return(Data);void IC_Write_Data(unsigned char Data)unsigned char write_time;unsigned char write_data;write_data=Data;for(write_time=0;write_time=2;write_time+)IC_Start();IC_Write_Byte(0x40);IC_Receive_Ack();IC_Write_Byte(write_data);IC_Receive_Ack();IC_Stop();if(IC_Err_Flag=0)break;unsigned char IC_Read_Data(void)unsigned char Return_Data;unsigned char read_time;for(read_time=0;read_time=2;read_time+)IC_Start();IC_Write_Byte(0x41);IC_Receive_Ack();Return_Data=IC_Read_Byte();IC_Send_NAck();IC_Stop();if(IC_Err_Flag=0)return(Return_Data);break;void PCF8574_Init(void)IC_Write_Data(0xf0);/输入状态的必须开始的时候置为1，输出为0void main(void)unsigned char temp3;Timer0_Init();PCF8574_Init();while(1)temp3=IC_Read_Data();IC_Write_Data(0x0f);Delay();；中间可以添加你需要的模块，比如显示或者其他的操作等/* 中断服务子程序 */extern void external0_rt(void)interrupt 0/INT0extern void eit0_rt(void)interrupt 1/T0，标准，定时中断TH0=0x1e;TL0=0x0c;IC_Re_Time+;void external1_rt(void)interrupt 2 using 1/INT1void eit1_rt(void)interrupt 3 using 1/T1，标准void sci_rt(void)interrupt 4 using 1/UARTvoid eit2_rt(void)interrupt 5 using 1/T2 3