temp_3.c

C & Asm source code for cygnal microcontrollers C8051F3xx.

//-----------------------------------------------------------------------------
// Temp_3.c
//-----------------------------------------------------------------------------
// Copyright 2001 Cygnal Integrated Products, Inc.
//
// AUTH: BW
// DATE: 12 OCT 01
//
// This program prints the C8051F30x die temperature out the hardware 
// UART at 9600bps. Uses the calibrated internal 24.5MHz oscillator as the 
// system clock source.
//
// 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
// <result>, which contains the accumulated result. 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> = 4096 gain you 6 bits of resolution: 4^6 = 4096.
//
// Target: C8051F30x
// Tool chain: KEIL C51 6.03 / KEIL EVAL C51
//

//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051f300.h>                 // SFR declarations
#include <stdio.h>

//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F30x
//-----------------------------------------------------------------------------

sfr16 DP       = 0x82;                 // data pointer
sfr16 TMR2RL   = 0xca;                 // Timer2 reload value
sfr16 TMR2     = 0xcc;                 // Timer2 counter
sfr16 PCA0CP1  = 0xe9;                 // PCA0 Module 1 Capture/Compare
sfr16 PCA0CP2  = 0xeb;                 // PCA0 Module 2 Capture/Compare
sfr16 PCA0     = 0xf9;                 // PCA0 counter
sfr16 PCA0CP0  = 0xfb;                 // PCA0 Module 0 Capture/Compare

//-----------------------------------------------------------------------------
// Global CONSTANTS
//-----------------------------------------------------------------------------

#define SYSCLK       24500000          // SYSCLK frequency in Hz
#define BAUDRATE     9600              // Baud rate of UART in bps
#define SAMPLE_RATE  100000            // Sample frequency in Hz
#define INT_DEC      4096              // integrate and decimate ratio

sbit LED = P0^2;                       // LED='1' means ON
sbit SW2 = P0^3;                       // SW2='0' means switch pressed

//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------

void SYSCLK_Init (void);
void PORT_Init (void);
void UART0_Init (void);
void ADC0_Init (void);
void Timer2_Init (int counts);
void ADC0_ISR (void);

//-----------------------------------------------------------------------------
// Global VARIABLES
//-----------------------------------------------------------------------------

long result;                           // ADC0 decimated value

//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------

void main (void) {
   long temperature;                   // temperature in hundredths of a
                                       // degree C
   int temp_int, temp_frac;            // integer and fractional portions of
                                       // temperature

   // Disable Watchdog timer
   PCA0MD &= ~0x40;                    // WDTE = 0 (clear watchdog timer 
                                       // enable)

   SYSCLK_Init ();                     // initialize oscillator
   PORT_Init ();                       // initialize crossbar and GPIO
   UART0_Init ();                      // initialize UART0
   Timer2_Init (SYSCLK/SAMPLE_RATE);   // initialize Timer2 to overflow at
                                       // sample rate

   ADC0_Init ();                       // init ADC0

	AD0EN = 1;                          // enable ADC0

   EA = 1;                             // Enable global interrupts

	while (1) {
      EA = 0;                          // disable interrupts
      temperature = result;
      EA = 1;                          // re-enable interrupts

      // calculate temperature in hundredths of a degree (14-bit full scale)
      temperature = temperature - 8700;
      temperature = (temperature * 10000L) / 3277;
      temp_int = temperature / 100;
      temp_frac = temperature - (temp_int * 100);
	   printf ("Temperature is %+02d.%02d\n", temp_int, temp_frac);

      LED = ~SW2;                      // LED reflects state of SW2
	}
}

//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// This routine initializes the system clock to use the internal 24.5MHz 
// oscillator as its clock source.  Also enables missing clock detector reset.
//
void SYSCLK_Init (void)
{
   OSCICL = 0x1c;                      // *** dummy calibration write to OSCICL

   OSCICN |= 0x03;                     // configure internal oscillator for
                                       // its maximum frequency}
   RSTSRC = 0x04;                      // enable missing clock detector
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports.
// P0.0 - 
// P0.1 -
// P0.2 - LED (push-pull)
// P0.3 - SW2
// P0.4 - UART TX (push-pull)
// P0.5 - UART RX
// P0.6 - 
// P0.7 - C2D
//
void PORT_Init (void)
{
   XBR0    = 0x0c;                     // skip LED and Switch in crossbar 
                                       // assignments
   XBR1    = 0x03;                     // UART0 TX and RX pins enabled
   XBR2    = 0x40;                     // Enable crossbar and weak pull-ups
   P0MDOUT |= 0x14;                    // enable TX0 and LED as a push-pull
                                       // outputs
}

//-----------------------------------------------------------------------------
// UART0_Init
//-----------------------------------------------------------------------------
//
// Configure the UART0 using Timer1, for <BAUDRATE> and 8-N-1.
//
void UART0_Init (void)
{
   SCON0 = 0x10;                       // SCON0: 8-bit variable bit rate
                                       //        level of STOP bit is ignored
                                       //        RX enabled
                                       //        ninth bits are zeros
                                       //        clear RI0 and TI0 bits
   if (SYSCLK/BAUDRATE/2/256 < 1) {
      TH1 = -(SYSCLK/BAUDRATE/2);
      CKCON |= 0x10;                   // T1M = 1; SCA1:0 = xx
   } else if (SYSCLK/BAUDRATE/2/256 < 4) {
      TH1 = -(SYSCLK/BAUDRATE/2/4);
      CKCON |=  0x01;                  // T1M = 0; SCA1:0 = 01
      CKCON &= ~0x12;
   } else if (SYSCLK/BAUDRATE/2/256 < 12) {
      TH1 = -(SYSCLK/BAUDRATE/2/12);
      CKCON &= ~0x13;                  // T1M = 0; SCA1:0 = 00
   } else {
      TH1 = -(SYSCLK/BAUDRATE/2/48);
      CKCON |=  0x02;                  // T1M = 0; SCA1:0 = 10
      CKCON &= ~0x11;
   }

   TL1 = 0xff;                         // set Timer1 to overflow immediately
   TMOD |= 0x20;                       // TMOD: timer 1 in 8-bit autoreload
   TMOD &= ~0xD0;                      // mode
   TR1 = 1;                            // START Timer1
   TI0 = 1;                            // Indicate TX0 ready
}

//-----------------------------------------------------------------------------
// ADC0_Init
//-----------------------------------------------------------------------------
//
// Configure ADC0 to use Timer2 overflows as conversion source, to
// generate an interrupt on conversion complete, and to sense the output of
// the temp sensor.  Enables ADC end of conversion interrupt. Leaves ADC 
// disabled.
//
void ADC0_Init (void)
{
   ADC0CN = 0x02;                      // ADC0 disabled; normal tracking
                                       // mode; ADC0 conversions are initiated 
                                       // on overflow of Timer2;
   AMX0SL = 0xf8;                      // select temp sensor as mux input
   ADC0CF = (SYSCLK/7500000) << 3;     // ADC conversion clock <= 7.5MHz
   ADC0CF |= 0x02;                     // PGA gain = 2
   REF0CN = 0x0e;                      // enable temp sensor, VREF = VDD, bias
                                       // generator is on.
   EIE1 |= 0x04;                       // enable ADC0 EOC interrupt
}

//-----------------------------------------------------------------------------
// Timer2_Init
//-----------------------------------------------------------------------------
//
// Configure Timer2 to auto-reload at interval specified by <counts> (no 
// interrupt generated) using SYSCLK as its time base.
//
void Timer2_Init (int counts)
{
   TMR2CN = 0x00;                      // STOP Timer2; Clear TF2H and TF2L;
                                       // disable low-byte interrupt; disable
                                       // split mode; select internal timebase
   CKCON |= 0x20;                      // Timer2 uses SYSCLK as its timebase

   TMR2RL  = -counts;                  // Init reload values
   TMR2    = 0xffff;                   // set to reload immediately
   ET2 = 0;                            // disable Timer2 interrupts
   TR2 = 1;                            // start Timer2
}

//-----------------------------------------------------------------------------
// 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 8 using 3
{
   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 >> 6;
      accumulator = 0L;                // reset accumulator
   }
}