K-type thermocouple program Proteus test based on ATMEGA8A microcontroller + MAX6675

Adopting avr series ATMEGA8A microcontroller, digital tube adopts 74hc595 static drive, reads MAX6675 chip and performs temperature conversion.



Cold junction compensation potassium thermocouple digital converter (0℃ to +1024℃)
MAX6675 performs cold junction compensation and digitizes the signal of K-type thermocouple. The data is output in 12-bit resolution, SPI compatible, read-only format. The converter can resolve the temperature to 0.25°C, the reading can reach up to +1024°C, and the thermocouple accuracy is 8 LSb in the range of 0°C to +700°C. MAX 6675 adopts small 8-pin SO4 package. Application ● Industry ● Home appliances ● HVAC

Features ● Direct digital conversion of K-type thermocouple output ● Cold junction compensation ● Simple SPI compatible serial interface ● 12 bits, 0.25°C resolution ● Open thermocouple detection



Simply put, read 16 binary, only the middle 3 to 14 are valid, take them out, and then multiply by the resolution 0.25 to get how many degrees Celsius.


The microcontroller source program is as follows:

1. #include
   

2. #include
   

3. 
   

4. #include
   

5. 
   

6. #define Date16 PORTD.5
   

7. #define CLK PORTD.7
   

8. #define RCLK PORTD.6
   

9. 
   

10. 
    

11. #define DateIN PINB.0
    

12. #define MCLK PORTB.1
    

13. #define CS PORTB.2
    

14. 
    

15. const unsigned char Dis_Code[] = {0xFC, 0x60, 0xDA, 0xF2, 0x66, 0XB6, 0xBE, 0xE0, 0XFE, 0xF6};
    

16. 
    

17. unsigned char Blk_Flg,Blk_Bit;
    

18. unsigned char Disp_Timer, Dis_Buffer[8];
    

19. 
    

20. unsigned int wendu,T_Timer;
    

21. 
    

22. 
    

23. 
    

24. 
    

25. unsigned int Read6675(void)
    

26. {
    

27. unsigned int date6675=0;
    

28. unsigned char i;
    

29.      CS=0;
    

30.      delay_us(15);
    

31.      MCLK=0;
    

32.      delay_us(15);
    

33.      for(i=0;i<16;i++)
    

34.      {
    

35. 
    

36.        date6675<<=1;
    

37.        delay_us(15);
    

38.        MCLK=1;
    

39.        delay_us(15);
    

40.        if(DateIN==1) date6675|=0X01;
    

41.        delay_us(15);
    

42.        MCLK=0;
    

43.        delay_us(15);
    

44.      }
    

45.      CS=1;
    

46.      delay_us(15);
    

47. //     MCLK=1;
    

48.      if((date6675&0X0004)!=0)   date6675=4095;
    

49.      else  date6675>>=3;
    

50.      return  date6675;
    

51. 
    

52. }
    

53. 
    

54. 
    

55. void T_zhuanhuan(void)
    

56. {
    

57.    float temp;
    

58.    temp=Read6675();
    

59.    temp*=2.5;
    

60.    wendu=(unsigned int)temp;
    

61. }
    

62. 
    

63. 
    

64. int EEPROMwrite( int location, unsigned char byte)
    

65. {
    

66.     unsigned char oldSREG;
    

67. 
    

68.     while (EECR & 0x02);
    

69. 
    

70.     EEAR = location;
    

71. 
    

72.     EEDR = byte;
    

73. 
    

74.     oldSREG = SREG;
    

75.     SREG &= ~0x80;
    

76. 
    

77.     EECR |= 0x04;
    

78.     EECR |= 0x02;
    

79. 
    

80.     SREG = oldSREG;
    

81.     return 0;
    

82. }
    

83. unsigned char EEPROMread( int location)
    

84. {
    

85.     while (EECR & 0x02);
    

86. 
    

87.     EEAR = location;
    

88. 
    

89.     EECR |= 0x01;
    

90. 
    

91.     return (EEDR);
    

92. }
    

93. 
    

94. 
    

95. void Disp_Led(void)
    

96. {
    

97.     unsigned char Dis_Temp_B1,Dis_Temp_B2,Dis_Temp_B3 ;
    

98.     RCLK=1 ;
    

99.     for(Dis_Temp_B1=0;Dis_Temp_B1<5;Dis_Temp_B1++)
    

100.     {
     

101.         Dis_Temp_B3=1 ;
     

102.         for(Dis_Temp_B2=0;Dis_Temp_B2<8;Dis_Temp_B2++)
     

103.         {
     

104.             if((Dis_Buffer[Dis_Temp_B1]&Dis_Temp_B3)!=0)
     

105.             Date16=1 ;
     

106.             else
     

107.             Date16=0 ;
     

108.             CLK=0 ;
     

109.             CLK=1 ;
     

110.             Dis_Temp_B3*=2 ;
     

111.         }
     

112.     }
     

113.     RCLK=0 ;
     

114.     RCLK=1 ;
     

115. }
     

116. void Dex_To_Bcd(int Dis_Value,unsigned char Blk_En,unsigned char Bcd_T_B1)
     

117. {
     

118.     Dis_Buffer[4]=Dis_Code[Dis_Value/10000];
     

119.     Dis_Value%=10000 ;
     

120.     Dis_Buffer[3]=Dis_Code[Dis_Value/1000];
     

121.     Dis_Value%=1000 ;
     

122.     Dis_Buffer[2]=Dis_Code[Dis_Value/100];
     

123.     Dis_Value%=100 ;
     

124.     Dis_Buffer[1]=Dis_Code[Dis_Value/10];
     

125.     Dis_Value%=10 ;
     

126.     Dis_Buffer[0]=Dis_Code[Dis_Value];
     

127.     if((Blk_Flg==1)&&(Blk_En!=0))
     

128.     {
     

129.         switch(Blk_Bit)
     

130.         {
     

131.             /*0*/
     

132.             case 0 :
     

133.             break ;
     

134.             /*1*/
     

135.             case 1 :
     

136.             if(Bcd_T_B1==4)Bcd_T_B1=3 ;
     

137.             break ;
     

138.             /*2*/
     

139.             case 2 :
     

140.             if(Bcd_T_B1==3||Bcd_T_B1==4)Bcd_T_B1=2 ;
     

141.             break ;
     

142.             /*3*/
     

143.             case 3 :
     

144.             if(Bcd_T_B1==2||Bcd_T_B1==3||Bcd_T_B1==4)Bcd_T_B1=1 ;
     

145.             break ;
     

146.             /*4*/
     

147.             case 4 :
     

148.             Bcd_T_B1=0 ;
     

149.             break ;
     

150.             default :
     

151.             break ;
     

152.         }
     

153.     }
     

154. 
     

155.     if(Bcd_T_B1==1&&Dis_Buffer[4]==0xFC)Dis_Buffer[4]=0x00 ;
     

156.     if(Bcd_T_B1==2&&Dis_Buffer[4]==0xFC)
     

157.     {
     

158.         Dis_Buffer[4]=0x00 ;
     

159.         if(Dis_Buffer[3]==0xFC)
     

160.         
     

161. ……………………