Temperature Unit Conversion
//----------------------------------------------------------------------------- // Temp_2.c // This program is a modified version of Temp_3.c that comes with the Cygnal // development system tools. It takes 256 samples of the temperature, averages // them, and stores the average in a global variable. In the main program, this // global variable is monitored, and the LED lights up if the temperature goes // above room temperature. // Assumes an 22.1184MHz crystal is attached between XTAL1 and XTAL2. // // The ADC is configured to look at the on-chip temp sensor. The sampling // rate of the ADC is determined by the constant <SAMPLE_RATE>, which is given // in Hz. // // The ADC0 End of Conversion Interrupt Handler retrieves the sample // from the ADC and adds it to a running accumulator. Every <INT_DEC> // samples, the ADC updates and stores its result in the global variable // <temperature>, which holds the current temperature in hundredths of a // degree. The sampling technique of adding a set of values and // decimating them (posting results every (n)th sample) is called 'integrate // and dump.' It is easy to implement and requires very few resources. // // For each power of 4 of <INT_DEC>, you gain 1 bit of effective resolution. // For example, <INT_DEC> = 256 gain you 4 bits of resolution: 4^4 = 256. // // Also note that the ADC0 is configured for 'LEFT' justified mode. In this // mode, the MSB of the ADC word is located in the MSB position of the ADC0 // high byte. Using the data in this way makes the magnitude of the resulting // code independent of the number of bits in the ADC (12- and 10-bits behave // the same). // // Target: C8051F02x // Tool chain: KEIL C51 6.03 / KEIL EVAL C51 //
//----------------------------------------------------------------------------- // Includes //-----------------------------------------------------------------------------
#include <c8051f020.h> // SFR declarations #include <stdio.h>
//----------------------------------------------------------------------------- // 16-bit SFR Definitions for 'F02x //-----------------------------------------------------------------------------
sfr16 DP = 0x82; // data pointer sfr16 TMR3RL = 0x92; // Timer3 reload value sfr16 TMR3 = 0x94; // Timer3 counter sfr16 ADC0 = 0xbe; // ADC0 data sfr16 ADC0GT = 0xc4; // ADC0 greater than window sfr16 ADC0LT = 0xc6; // ADC0 less than window sfr16 RCAP2 = 0xca; // Timer2 capture/reload sfr16 T2 = 0xcc; // Timer2 sfr16 RCAP4 = 0xe4; // Timer4 capture/reload sfr16 T4 = 0xf4; // Timer4 sfr16 DAC0 = 0xd2; // DAC0 data sfr16 DAC1 = 0xd5; // DAC1 data
//----------------------------------------------------------------------------- // Global CONSTANTS //-----------------------------------------------------------------------------
#define SYSCLK 22118400 // SYSCLK frequency in Hz #define SAMPLE_RATE 50000 // Sample frequency in Hz #define INT_DEC 256 // integrate and decimate ratio
sbit LED = P1^6; // LED='1' means ON sbit SW1 = P3^7; // SW1='0' means switch pressed
//----------------------------------------------------------------------------- // Function PROTOTYPES //-----------------------------------------------------------------------------
void SYSCLK_Init (void); void PORT_Init (void); void ADC0_Init (void); void Timer3_Init (int counts); void ADC0_ISR (void);
//----------------------------------------------------------------------------- // Global VARIABLES //-----------------------------------------------------------------------------
long result; // ADC0 decimated value
//----------------------------------------------------------------------------- // MAIN Routine //-----------------------------------------------------------------------------
void main (void) {
unsigned long temperature; // temperature in degrees C
WDTCN = 0xde; // disable watchdog timer
WDTCN = 0xad;
SYSCLK_Init (); // initialize oscillator
PORT_Init (); // initialize crossbar and GPIO
Timer3_Init (SYSCLK/SAMPLE_RATE); // initialize Timer3 to overflow at
// sample rate
ADC0_Init (); // init ADC
AD0EN = 1; // enable ADC
EA = 1; // Enable global interrupts
while (1) {
temperature = result;
if (temperature < 0xB230) LED = 0;
else LED = 1;
}
}
//----------------------------------------------------------------------------- // Initialization Subroutines //-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// This routine initializes the system clock to use an 22.1184MHz crystal
// as its clock source.
//
void SYSCLK_Init (void)
{
int i; // delay counter
OSCXCN = 0x67; // start external oscillator with
// 22.1184MHz crystal
for (i=0; i < 256; i++) ; // XTLVLD blanking interval (>1ms)
while (!(OSCXCN & 0x80)) ; // Wait for crystal osc. to settle
OSCICN = 0x88; // select external oscillator as SYSCLK
// source and enable missing clock
// detector
}
//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports
//
void PORT_Init (void)
{
XBR0 = 0x04; // Enable UART0
XBR1 = 0x00;
XBR2 = 0x40; // Enable crossbar and weak pull-ups
P0MDOUT |= 0x01; // enable TX0 as a push-pull output
P1MDOUT |= 0x40; // enable P1.6 (LED) as push-pull output
}
//-----------------------------------------------------------------------------
// ADC0_Init
//-----------------------------------------------------------------------------
//
// Configure ADC0 to use Timer3 overflows as conversion source, to
// generate an interrupt on conversion complete, and to use left-justified
// output mode. Enables ADC end of conversion interrupt. Leaves ADC disabled.
//
void ADC0_Init (void)
{
ADC0CN = 0x05; // ADC0 disabled; normal tracking
// mode; ADC0 conversions are initiated
// on overflow of Timer3; ADC0 data is
// left-justified
REF0CN = 0x07; // enable temp sensor, on-chip VREF,
// and VREF output buffer
AMX0SL = 0x0f; // Select TEMP sens as ADC mux output
ADC0CF = (SYSCLK/2500000) << 3; // ADC conversion clock = 2.5MHz
ADC0CF |= 0x01; // PGA gain = 2
EIE2 |= 0x02; // enable ADC interrupts }
//-----------------------------------------------------------------------------
// Timer3_Init
//-----------------------------------------------------------------------------
//
// Configure Timer3 to auto-reload at interval specified by <counts> (no
// interrupt generated) using SYSCLK as its time base.
//
void Timer3_Init (int counts)
{
TMR3CN = 0x02; // Stop Timer3; Clear TF3;
// use SYSCLK as timebase
TMR3RL = -counts; // Init reload values
TMR3 = 0xffff; // set to reload immediately
EIE2 &= ~0x01; // disable Timer3 interrupts
TMR3CN |= 0x04; // start Timer3
}
//----------------------------------------------------------------------------- // Interrupt Service Routines //-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// ADC0_ISR
//-----------------------------------------------------------------------------
//
// ADC0 end-of-conversion ISR
// Here we take the ADC0 sample, add it to a running total <accumulator>, and
// decrement our local decimation counter <int_dec>. When <int_dec> reaches
// zero, we post the decimated result in the global variable <result>.
//
void ADC0_ISR (void) interrupt 15
{
static unsigned int_dec=INT_DEC; // integrate/decimate counter
// we post a new result when
// int_dec = 0
static long accumulator=0L; // here's where we integrate the
// ADC samples
AD0INT = 0; // clear ADC conversion complete
// indicator
accumulator += ADC0; // read ADC value and add to running
// total
int_dec--; // update decimation counter
if (int_dec == 0) { // if zero, then post result
int_dec = INT_DEC; // reset counter
result = accumulator >> 8;
accumulator = 0L; // reset accumulator
}
}