analog.c

8051 Web Server project See Makefile for build notes Written for Keil C51 V5.1 compiler, notes:

//-----------------------------------------------------------------------------
// Net ANALOG.C
//
// This module handles the analog inputs which are external temperature
// sensor, the on-chip temperature sensor, and operating voltage.
//-----------------------------------------------------------------------------
#include <string.h>
#include <stdlib.h>
#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 = MUX_CPU_VOLTS;		// Select AIN1 for next read
			mux_select = MUX_CPU_VOLTS;
		break;

		case MUX_CPU_VOLTS:
			temp_long = ADC0;
			temp_long = 24*temp_long/655*10;
			cpu_voltage = temp_long;
			AMX0SL = MUX_AIR_TEMP;		// Select on-chip temp sensor
			mux_select = MUX_AIR_TEMP;
		break;

		case MUX_AIR_TEMP:
			temp_long = ADC0;
			temp_long = 24*temp_long/655*2;
			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;
  	}
}