The reason of choosing DS1821 thermo sensor is that the circuit is very simple, it only need on IO pin.
Originally, I wrote the test program by SDCC compiler, the test has some problem, the LCD display is work, but the temperature is still display zero?
Then, I did compiling by HI-TECH's PICC, the temperature value is correct.
If you are using PICC, please comment out lines as following:
typedef unsigned int config;
config at 0x2007 __CONFIG = _XT_OSC & _PWRTE_OFF & _BODEN_OFF & _WDT_OFF & _LVP_OFF;
Replace pic/pic16f877a.h by htc.h
Circuit schematics is as following:
Main process:
/*******************************************************************************
Copyright (c) 2008 Wizign Ltd.
All Rights Reserved.
main.c: Main program for demo thermometer
Version: 1.0.0
Date: Sep 05, 2008
Author: YenHung Chen
E-mail: yhchen@wizign.com
Revision:
---------- -----------------------------------------------------------------
2008/09/05 Created by YenHung Chen, demo thermometer for both 8051 and PIC
******************************************************************************/
/*******************************************************************************
The IO control
<>For AT89S52
LCD display:
There are 8 data pins, which are connected P2.
The control pins are connected to P1_0, P1_1, and P1_2.
DS1821:
P1_7
<>For PIC16F877A
LCD display:
There are 8 data pins, which are connected PORTD
The control pins are connected to RA0, RA1, and RA2.
DS1821:
RA5
******************************************************************************/
#include "global.h"
#include "delay.h"
#include "lcd.h"
#include "thermo.h"
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// define IO and global variables
#ifdef MCU_PIC
// Configurations
typedef unsigned int config;
config at 0x2007 __CONFIG = _XT_OSC & _PWRTE_OFF & _BODEN_OFF & _WDT_OFF & _LVP_OFF;
#endif
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// define functions
/* Initilize parameters before run the main loop */
void InitParams(void)
{
LCDInit();
ThermoInit();
}
/* Display message on LCD panel */
void DisplayTemperature(void)
{
char tmMsg[16];
int theT;
unsigned char myT;
int hundred;
int tenth;
int ones;
LCDGoto(0); // goto 1st line
LCDPuts(" WIZIGN LTD. ");
// Convert value to string
myT = ThermoReadTemperature();
if(myT > 127){
theT = (int)(myT - 0xFF);
}else{
theT = (int)myT;
}
// start
// it can not display correct format in this block
BLOCK
// end
hundred = (int)(theT/100);
tenth = (int)((theT%100)/10);
ones = theT%10;
tmMsg[1] = 0x30 + hundred;
tmMsg[2] = 0x30 + tenth;
tmMsg[3] = 0x30 + ones;
tmMsg[4] = 0x20;
tmMsg[5] = 'C';
tmMsg[6] = 0x20;
tmMsg[7] = '\0';
LCDGoto(0x40); // goto 2nd line
LCDPuts(tmMsg);
}
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// main program
void main(void)
{
// Initilize parameters
InitParams();
/* do loop */
while(1){
DisplayTemperature();
// The LCD display and the calculation of time
// will consume times, so, the delay time is less than 1000 ms.
DelayMs(900);
}
}
