基于單片機的溫度測量方案

三、電路圖

我在這里用的是芯片PIC18F2550，它可以與任何其他規(guī)模較小的PIC微控制器實現I2C通信。溫度由TC74傳感器讀取并顯示在LCD字符。別忘 了把兩個上拉電阻（1K）連接在SDA和SCL線I2C總線上。在本實驗中采用PIC18F2550單片機PIC板來自于StartUSB for PIC board.。

圖4 電路圖

圖5 實物圖

圖6 TC74溫度傳感器

四、軟件

PIC18F2550固件是在C使用MikroC Pro for PIC編譯開發(fā)的。MikroC Pro for PIC編譯器提供的內置支持I2C庫。單片機讀取TC74內部溫度寄存器溫度字并顯示在LCD。下面的程序顯示，TC74的整個工作范圍內在40 至125°C。

程序：

/* Project: Using TC74 with PIC microcontroller

for temperature measurement

MCU: PIC18F2550 on-board StartUSB for PIC

Clock 48.0 MHz using HS + PLL

MCLR Enabled

*/

// Define LCD module connections.

sbit LCD_RS at RC6_bit;

sbit LCD_EN at RC7_bit;

sbit LCD_D4 at RB4_bit;

sbit LCD_D5 at RB5_bit;

sbit LCD_D6 at RB6_bit;

sbit LCD_D7 at RB7_bit;

sbit LCD_RS_Direction at TRISC6_bit;

sbit LCD_EN_Direction at TRISC7_bit;

sbit LCD_D4_Direction at TRISB4_bit;

sbit LCD_D5_Direction at TRISB5_bit;

sbit LCD_D6_Direction at TRISB6_bit;

sbit LCD_D7_Direction at TRISB7_bit;

// End LCD module connection definition

unsigned char Temp;

unsigned short num;

const int TC74A0 = 0x90;

void check_device(unsigned short dev_address){ I2C1_Start();

if (I2C1_Wr(dev_address)){ Lcd_Out(1,1,"Device not found");

}

else Lcd_Out(1,1,"TC74 device");

I2C1_Stop();

}

unsigned short Read_Temp(){

unsigned short result; I2C1_Start(); // Issue start signal

I2C1_Wr(TC74A0); // Address + Write bit

I2C1_Wr(0x00); // Read Temp

I2C1_Repeated_Start(); // Issue start signal

I2C1_Wr(TC74A0+1); // Address + Read bit

result = I2C1_Rd(0u); return result;

}