therm_1.c

Low End Microchip PICs C函数

// Program THERM_1.C
//
// Illustrates the use of Timer 1 with the external 32.768 kHz crystal T1OSC0
// and T1OSC1.
//
// Each second, briefly blips the speaker and displays the elapsed time in
// seconds and in hour:minute:sec format on the LCD.  Also performs A/D conversion
// on A/D Ch 1 and displays the temperature is degrees C and F.
//
// copyright, Peter H. Anderson, Baltimore, MD, Dec, '00

#case

#device PIC16F877 *=16 ICD=TRUE

#include <defs_877.h>
#include <lcd_out.h> // LCD and delay routines
#include <math.h>

#define TRUE !0
#define FALSE 0

#define THERM_A 0.0004132
#define THERM_B 0.000320135

struct TM
{
    byte hr;
    byte mi;
    byte se;
};

float calc_T_C(long ad_val);
float T_C_to_T_F(float T_C);
long meas_ad1(void);

void blip_tone(void);
void increment_time(struct TM *t);

byte timer1_int_occ;    // note that this is global

main()
{

   long elapsed_t, ad_val;
   struct TM t;
   float T_F, T_C;

   pcfg3 = 0; pcfg2 = 1; pcfg1 = 0; pcfg0 = 0;
   // config A/D for 3/0

   lcd_init();

   pspmode = 0;
   portd0 = 0;    // make speaker an ouput 0
   trisd0 = 0;

   // Set up timer2
   PR2 = 250;    // period set to 250 * 4 usecs  = 1 ms

   // Timer 2 post scale set to 1:1
   toutps3 = 0;  toutps2 = 0; toutps1 = 0; toutps0 = 0;

   // Timer 2 prescale set to 1:4
   t2ckps1 = 0; t2ckps0 = 1;

   // Set up timer1
   t1oscen = 1;   // enable external crystal osc circuitry
   tmr1cs = 1;    // select this as the source

   t1ckps1 = 0;   t1ckps0 = 0;   // prescale of 1

   tmr1if = 0;    // kill any junk interrupt
   TMR1L = 0x00;
   TMR1L = 0x80;

   tmr1ie = 1;
   peie = 1;
   gie = 1;

   timer1_int_occ = FALSE;

   elapsed_t = 0;                // start with elapsed time = 0
   t.hr = 0;  t.mi = 0; t.se = 0;

   tmr1on = 1;

   while(1)
   {
       if (timer1_int_occ)
       {
           blip_tone();
           timer1_int_occ = FALSE;
           ++elapsed_t;
           increment_time(&t);
           lcd_cursor_pos(0, 0);
           printf(lcd_char, "%ld    ", elapsed_t);

           lcd_cursor_pos(1, 0);
           lcd_dec_byte(t.hr, 2);
           lcd_char(':');
           lcd_dec_byte(t.mi, 2);
           lcd_char(':');
           lcd_dec_byte(t.se, 2);

           ad_val = meas_ad1();

           if (ad_val == 0)
           {
               ad_val = 1;      // avoid a divide by zero error
           }

           T_C = calc_T_C(ad_val);
           T_F = T_C_to_T_F(T_C);

           lcd_cursor_pos(2, 0);
           printf(lcd_char, "T_C = %3.1f  ", T_C);
           lcd_cursor_pos(3, 0);
           printf(lcd_char, "T_F = %3.1f  ", T_F);
       }
       // else do nothing
   }
}

float calc_T_C(long ad_val)
{
    float ad_val_float, r_therm, T_K, T_C;

    ad_val_float = (float) ad_val;
    r_therm = 10.0e3 / (1024.0/ad_val_float - 1.0);
    T_K = 1.0 / (THERM_A + THERM_B * log(r_therm));
    T_C = T_K - 273.15;
    return(T_C);
}

float T_C_to_T_F(float T_C)
{
    float T_F;
    T_F = T_C * 1.8 + 32.0;
    return(T_F);
}

long meas_ad1(void)
{
    long ad_val;

    adfm = 1;                 // right justified
    adcs1 = 1; adcs0 = 1;     // internal RC

    adon=1;                   // turn on the A/D
    chs2=0;  chs1=0;   chs0=1;   // channel 1
    delay_10us(10);      // a brief delay

    adgo = 1;
    while(adgo)    ;  // poll adgo until zero
    ad_val = ADRESH;
    ad_val = ad_val << 8 | ADRESL;
    adon = 0;
    return(ad_val);
}

void blip_tone(void)
{
   tmr2ie = 1;    // turn on timer 2 and enable interrupts
   peie = 1;
   tmr2on = 1;
   gie = 1;

   delay_ms(200); // tone for nominally 200 ms

   tmr2ie = 0;
   tmr2on = 0;
}

void increment_time(struct TM *t)
{
    ++t->se;
    if (t->se > 59)
    {
        t->se = 0;
        ++t->mi;
        if (t->mi > 59)
        {
            t->mi = 0;
            ++t->hr;
            if (t->hr > 23)
            {
                t->hr = 0;
            }
        }
    }
}

#int_timer1 timer1_int_handler(void)
{
    timer1_int_occ = TRUE;
    TMR1H = 0x80;
}

#int_timer2 timer2_int_handler(void)
{
    portd0 = !portd0;
}

#include <lcd_out.c>