www.pudn.com > WEB020.rar > Analog.c

//----------------------------------------------------------------------------- 
// Copyright (c) 2002 Jim Brady 
// Do not use commercially without author's permission 
// Last revised August 2002 
// Net ANALOG.C 
// 
// This module handles the analog inputs which are external temperature 
// sensor, the on-chip temperature sensor, and operating voltage. 
//----------------------------------------------------------------------------- 
#include  
#include  
#include "C8051f.h" 
#include "net.h" 
#include "serial.h" 
#include "analog.h" 
 
extern char xdata text[]; 
UINT idata cpu_temperature, air_temperature, cpu_voltage; 
UCHAR idata mux_select; 
 
sfr16 ADC0     = 0xbe;                 // ADC0 data 
 
//-------------------------------------------------------------------------- 
// Initialize the A/D converter 
//  
//-------------------------------------------------------------------------- 
void init_adc(void) 
{ 
	ADC0CN = 0x81;                      // ADC0 enabled; normal tracking 
     	                                // mode; ADC0 conversions are initiated  
                                       	// on write to AD0BUSY; ADC0 data is 
                                       	// left-justified 
	REF0CN = 0x07;                      // enable temp sensor, on-chip VREF, 
                                       	// and VREF output buffer 
	mux_select = MUX_CPU_TEMP;	  		// CPU on-chip temp sensor 
	AMX0SL = MUX_CPU_TEMP; 	 
 
   ADC0CF = (SYSCLK/2500000) << 3;     // ADC conversion clock = 2.5MHz 
 //  ADC0CF |= 0x01;                     // PGA gain = 2 
   EIE2 &= ~0x02;                      // disable ADC0 EOC interrupt 
   EIE1 &= ~0x04;                      // disable ADC0 window compare interrupt 
} 
 
 
 
//-------------------------------------------------------------------------- 
// This function is a little state machine which reads one analog 
// inputs at a time, out of the 3 possible inputs 
//  1. On-chip temperature 
//  2. External air temperature 
//  3. CPU operating voltage 
//-------------------------------------------------------------------------- 
void read_analog_inputs(void) 
{ 
   	ULONG idata temp_long; 
 
    AD0INT = 0;                      // clear conversion complete indicator 
    AD0BUSY = 1;                     // initiate conversion 
    while (AD0INT == 0);             // wait for conversion complete 
	switch (mux_select) 
	{ 
		case MUX_CPU_TEMP: 
	      	temp_long = ADC0 - 42380/2; 
		    temp_long= (temp_long * 200L) / 156; 
			cpu_temperature=temp_long; 
			AMX0SL = 0x00;		// Select AIN1 for next read 
			mux_select = MUX_CPU_VOLTS; 
		break; 
 
		case MUX_CPU_VOLTS: 
			temp_long = ADC0; 
			temp_long = 24*temp_long/6552; 
			cpu_voltage = temp_long; 
			AMX0SL = 0x01;		// Select on-chip temp sensor 
			mux_select = MUX_AIR_TEMP; 
		break; 
 
		case MUX_AIR_TEMP: 
			temp_long = ADC0; 
			temp_long = 33*temp_long/6552; 
			air_temperature = temp_long; 
			AMX0SL = MUX_CPU_TEMP;	  
			mux_select = MUX_CPU_TEMP; 
		break; 
 
		default: 
			AMX0SL = MUX_CPU_TEMP; 
			mux_select = MUX_CPU_TEMP; 
		break; 
  	} 
}