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研发客服硬件：max6675 STC12C5A60S2 K型热电偶
功能：实现读取K型热电偶温度，并通过上位机打印出实际温度
难点：读取Max6675的数据是16位，而STC12系列单片机每次接收的数据为8位，如何通过硬件SPI实现直接读取Max6675的温度成为一难点。网上相关教程以及相关论文均是采用软件SPI模拟时序方式采集数据，故而通过STC12系列单片机自带的硬件SPI实现直接读取Max6675的数据具有实际研究意义。
代码：
#include "reg51.h"
#include "stdio.h"
#include
#define MASTER //define:master undefine:slave
#define FOSC 11059200L
#define BAUD (256 - FOSC / 32 / 9600) //253
typedef unsigned char BYTE;
typedef unsigned int WORD;
typedef unsigned long DWORD;
sfr AUXR = 0x8e; //Auxiliary register
sfr SPSTAT = 0xcd; //SPI status register
#define SPIF 0x80 //SPSTAT.7
#define WCOL 0x40 //SPSTAT.6
sfr SPCTL = 0xce; //SPI control register
#define SSIG 0x80 //SPCTL.7
#define SPEN 0x40 //SPCTL.6
#define DORD 0x20 //SPCTL.5
#define MSTR 0x10 //SPCTL.4
#define CPOL 0x08 //SPCTL.3
#define CPHA 0x04 //SPCTL.2
#define SPDHH 0x00 //CPU_CLK/4
#define SPDH 0x01 //CPU_CLK/16
#define SPDL 0x02 //CPU_CLK/64
#define SPDLL 0x03 //CPU_CLK/128
sfr SPDAT = 0xcf; //SPI data register
sbit SPISS = P1^3; //SPI slave select, connect to slave' SS(P1.4) pin
void InitUart();
void InitSPI();
void SendUart(BYTE dat); //send data to PC
BYTE RecvUart(); //receive data from PC
unsigned int SPISwap(); //swap SPI data between master
void Delay_xms(unsigned int z){
unsigned char i, j;
unsigned int k;
for(k=0;k
_nop_();
i = 12;
j = 84;
do{while (--j);}
while (--i);
}
}
///////////////////////////////////////////////////////////
void main()
{
unsigned int t;
unsigned int a= 0x01;
unsigned int MAX6675_Temp;
unsigned char Flag_connect;
InitUart(); //initial UART
InitSPI(); //initial SPI
while (1)
{
// #ifdef MASTER //for master (receive UART data from PC and send it to slave,
// // in the meantime receive SPI data from slave and send it to PC)
// SendUart(SPISwap(RecvUart()));
// #else //for salve (receive SPI data from master and
// ACC = SPISwap(ACC); // send previous SPI data to master)
// printf("dd");
// #endif
t=SPISwap();
Flag_connect=t&0x04; //¶Á³öÊý¾ÝµÄD2λÊÇÈȵçżµôÏß±ê־룬¸ÃλΪ1±íʾµôÏߣ¬¸ÃλΪ0±íʾÁ¬½Ó
Flag_connect=Flag_connect>>2; //MAX6675ÊÇ·ñÔÚÏß
t = t<<1; //¶Á³öÀ´µÄÊý¾ÝµÄD3~D14ÊÇζÈÖµ
t = t>>4;
MAX6675_Temp = t/4-28; //²âµÃµÄζȵ¥Î»ÊÇ0.25£¬ËùÒÔÒª³ËÒÔ0.25£¨¼´³ýÒÔ4£©²ÅÄܵõ½ÒÔ¶ÈΪµ¥Î»µÄζÈÖµ
if(Flag_connect==0) //Flag_connectΪ0±íʾÈȵçżÒÑÁ¬½Ó£¬ÕâʱÏÔʾζÈ
{
printf("%dn",MAX6675_Temp);
}
else
{
printf("δÁ¬ÉÏn");
}
// printf("%dn",t);
//// printf("%d n",t/4);
Delay_xms(1000);
}
}
///////////////////////////////////////////////////////////
void InitUart()
{
SCON = 0x5a; //set UART mode as 8-bit variable baudrate
TMOD = 0x20; //timer1 as 8-bit auto reload mode
AUXR = 0x40; //timer1 work at 1T mode
TH1 = TL1 = BAUD; //115200 bps
TR1 = 1;
}
///////////////////////////////////////////////////////////
void InitSPI()
{
SPDAT = 0; //initial SPI data
SPSTAT = SPIF | WCOL; //clear SPI status
#ifdef MASTER
SPCTL = SPEN | MSTR; //master mode
#else
SPCTL = SPEN; //slave mode
#endif
}
///////////////////////////////////////////////////////////
void SendUart(BYTE dat)
{
while (!TI); //wait pre-data sent
TI = 0; //clear TI flag
SBUF = dat; //send current data
}
///////////////////////////////////////////////////////////
BYTE RecvUart()
{
while (!RI); //wait receive complete
RI = 0; //clear RI flag
return SBUF; //return receive data
}
///////////////////////////////////////////////////////////
unsigned int SPISwap()
{
unsigned int temp=0;
SPISS = 0; //pull low slave SS
SPDAT = 25; //trigger SPI send
while (!(SPSTAT & SPIF)); //wait send complete
SPSTAT = SPIF | WCOL; //clear SPI statusa
temp = SPDAT;
temp = temp << 8;
SPDAT = 45;
while (!(SPSTAT & SPIF)); //wait send complet
temp = temp | SPDAT;
SPSTAT = SPIF | WCOL; //clear SPI status
SPISS = 1; //push high slave SS
return temp; //return received SPI data
}