一个简单的onewire(单总线)温度测试小程序

        onewire(单总线)是DALLAS公司推出的外围串行扩展总线，传输时钟信号又传输数据，而且能够进行双向通信，具有节省I/O口线、资源结构简单、成本低廉、便于总线扩展和维护等诸多优点。常用到单总线的器件，一般是稳定传感器，如DS18B20、DS2431。

以下是一个简单的onewire(单总线)温度测试程序，希望大家能够喜欢。

1. // LCD module connections
   
2. sbit LCD_RS at P2_0_bit;
   
3. sbit LCD_EN at P2_1_bit;
   
4. 
   
5. sbit LCD_D4 at P2_2_bit;
   
6. sbit LCD_D5 at P2_3_bit;
   
7. sbit LCD_D6 at P2_4_bit;
   
8. sbit LCD_D7 at P2_5_bit;
   
9. // End LCD module connections
   
10. 
    
11. // OneWire pinout
    
12. sbit OW_Bit at P1_2_bit;
    
13. // end OneWire definition
    
14. 
    
15. 
    
16. //  Set TEMP_RESOLUTION to the corresponding resolution of used DS18x20 sensor:
    
17. //  18S20: 9  (default setting; can be 9,10,11,or 12)
    
18. //  18B20: 12
    
19. const unsigned short TEMP_RESOLUTION = 9;
    
20. 
    
21. char *text = "000.0000";
    
22. unsigned temp;
    
23. 
    
24. void Display_Temperature(unsigned int temp2write) {
    
25.   const unsigned short RES_SHIFT = TEMP_RESOLUTION - 8;
    
26.   char temp_whole;
    
27.   unsigned int temp_fraction;
    
28. 
    
29.   // check if temperature is negative
    
30.   if (temp2write & 0x8000) {
    
31.     text[0] = '-';
    
32.     temp2write = ~temp2write + 1;
    
33.   }
    
34. 
    
35.   // extract temp_whole
    
36.   temp_whole = temp2write >> RES_SHIFT;
    
37. 
    
38.   // convert temp_whole to characters
    
39.   if (temp_whole/100)
    
40.      text[0] = temp_whole/100  + 48;
    
41.   else
    
42.      text[0] = '0';
    
43. 
    
44.   text[1] = (temp_whole/10)%10 + 48;             // Extract tens digit
    
45.   text[2] =  temp_whole%10     + 48;             // Extract ones digit
    
46. 
    
47.   // extract temp_fraction and convert it to unsigned int
    
48.   temp_fraction  = temp2write << (4-RES_SHIFT);
    
49.   temp_fraction &= 0x000F;
    
50.   temp_fraction *= 625;
    
51. 
    
52.   // convert temp_fraction to characters
    
53.   text[4] =  temp_fraction/1000    + 48;         // Extract thousands digit
    
54.   text[5] = (temp_fraction/100)%10 + 48;         // Extract hundreds digit
    
55.   text[6] = (temp_fraction/10)%10  + 48;         // Extract tens digit
    
56.   text[7] =  temp_fraction%10      + 48;         // Extract ones digit
    
57. 
    
58.   // print temperature on LCD
    
59.   Lcd_Out(2, 5, text);
    
60. }
    
61. 
    
62. void main() {
    
63. 
    
64.   Lcd_Init();                                    // Initialize LCD
    
65.   Lcd_Cmd(_LCD_CLEAR);                           // Clear LCD
    
66.   Lcd_Cmd(_LCD_CURSOR_OFF);                      // Turn cursor off
    
67.   Lcd_Out(1, 1, " Temperature:   ");
    
68.   // Print degree character, 'C' for Centigrades
    
69.   Lcd_Chr(2,13,223);  // different LCD displays have different char code for degree
    
70.                       // if you see greek alpha letter try typing 178 instead of 223
    
71. 
    
72.   Lcd_Chr(2,14,'C');
    
73. 
    
74.   //--- main loop
    
75.   do {
    
76.     //--- perform temperature reading
    
77.     Ow_Reset();                                  // Onewire reset signal
    
78.     Ow_Write(0xCC);                              // Issue command SKIP_ROM
    
79.     Ow_Write(0x44);                              // Issue command CONVERT_T
    
80.     Delay_us(120);
    
81. 
    
82.     Ow_Reset();
    
83.     Ow_Write(0xCC);                              // Issue command SKIP_ROM
    
84.     Ow_Write(0xBE);                              // Issue command READ_SCRATCHPAD
    
85. 
    
86.     temp =  Ow_Read();
    
87.     temp = (Ow_Read() << 8) + temp;
    
88. 
    
89.     //--- Format and display result on Lcd
    
90.     Display_Temperature(temp);
    
91. 
    
92.     Delay_ms(500);
    
93.   } while (1);
    
94. }
    

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