主从单片机通讯实例.doc

最近在开发一个单片机多机通信系统,主从式分布,请问如何给从机分配地址?主机发送广播询问地址时,从机如何校验地址?用C如何编写代码?以一主机,2从机为例
单片机a,b,c. a为主机,bc为从机。a上有一个外部中断0输入,按第一次a的两个LED亮500ms,再按一下,b机的两个LED灯亮500ms,第三次按下c机的两个LED灯亮500ms,然后周而复始。两个数码管分别显示0/1/2, 和abc(bc由从机反馈)
/*
主从通信基本步骤:
1. 主机从机初始化为方式2或者3,从机都置SM2=1,允许中断
2. 主机置TB8=1,发送从机地址
3. 所有从机均接收主机发送要寻址的从机地址
4. 被寻址的从机确认地址后,置本机SM2=0,向主机返回地址,供主机核对
5. 核对无误后,主机向被寻址的从机发送命令,通知从机接受或者发送数据。
6. 本次通信结束后,主从机重置SM2=1,主机可再对其他从机寻址
*/
******************************************************************
主机a:
******************************************************************
#include <>
#define uchar unsigned char
#define uint unsigned int
uchar leddata[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x77,0x7C,0x39,0x5E,0x79,0x71,0x40,0x00};
uchar Mode;
sbit P10 = P1^0;
sbit P13 = P1^3;
sbit P17 = P1^7;
sbit P20 = P2^0;
sbit P21 = P2^1;
void UART_init()
{
TMOD = 0x20;
TH1 = 0xfd;
TL1 = 0xfd;
TR1 = 1;
SCON = 0xd0;
ES = 1;
EX0 = 1;
IT0 = 1; //INT0下跳触发
EA = 1;
TI = 0;
}
void DelayMs(int ms)
{
uchar i;
while(ms--)
for(i=0; i<120; i++);
}
void putc_to_SerialPort(uchar c)
{
SBUF = c;
while(TI == 0);
TI = 0;
}
void MasterControl(unsigned char Addr, unsigned d)
{
TB8 = 1;
putc_to_SerialPort(Addr);
DelayMs(50);
TB8 = 0;
d);
DelayMs(50);
}
Ex0_int(void) interrupt 0
{
P0 = leddata[Mode];
P20 = 0;
if(Mode == 0)
{
P2 = leddata[10];
P10 = 0;
P13 = 0;
DelayMs(500);
P10 = 1;
P13 = 1;
// MasterControl('b','C');
// MasterControl('c','C');
}
else if(Mode == 1)
{
P10 = 1;
P13 = 1;
MasterControl('b','O');
// MasterControl('c','C');
}
else if(Mode == 2)
{
P10 = 1;
P13 = 1;
// MasterControl('b','C');
MasterControl('c','O');
}
Mode = (Mode + 1) % 3;
}
com_int(void) interrupt 4
{
if(RI)
{
RI = 0;
if(SBUF == 'b')
{
P2 = leddata[11];
}
if(SBUF == 'c')
{
P2 = leddata[12];
}
}
}
void main(void)
{
P0 = 0x00;
P1 = 0xff;
P2 = 0x00;
UART_init();