example_6_pwm.c

CYGNAL单片机

//-----------------------------------------------------------------------------
// Example 6
// PWM using PCA High Speed Output Mode
//-----------------------------------------------------------------------------
// Copyright 2004 Silicon Laboratories Inc.
//
// AUTH: KAB
// DATE: 12MAR04
//
// This example demonstrates using the High Speed Output (HSO) mode to
// generate a PWM signal.
//
// The program reads the value of a potentiometer connected to P0.6 and uses
// this value to set the duty Cycle of the PWM. This example could be used
// to drive a dc motor.
//
// Target: C8051F30x
//
// Tool chain: KEIL Eval 'c'
//
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051f300.h>                 // SFR declarations

//-----------------------------------------------------------------------------
// typedefs
//-----------------------------------------------------------------------------

typedef union                          // union used for writing to TL0 & TH0
    {
        struct
        {
            unsigned char hi;
            unsigned char lo;
        } b;
        unsigned int w;
    }udblbyte;

//-----------------------------------------------------------------------------
// MACROS (all caps)
//-----------------------------------------------------------------------------

#define SYSCLK       24500000          // SYSCLK frequency in Hz
#define PERIOD (SYSCLK/20000)
#define DEADTIME 25                    // desired Dead-Time in clocks
#define LATENCY 45                     // worst case latency in clocks
#define HTSPAN (PERIOD - 2*LATENCY)    // high-time span
//-----------------------------------------------------------------------------
// Global Variables
//-----------------------------------------------------------------------------

unsigned int HiTime;
unsigned int  NextEdge;
bit Cycle;
//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------
void SYSCLK_Init (void);
void PORT_Init (void);
void PCA0_Init (void);
void PCA0_ISR (void);
void ADC0_Init (void);
unsigned char readVin (void);
unsigned char avgVin (void);

//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------
void main (void) {

   unsigned long x;
   unsigned int y;



   PCA0MD &= ~0x40;                    // Disable Watchdog Timer

   SYSCLK_Init ();                     // Initialize system clock to
                                       // 24.5MHz internal oscillator
   PORT_Init ();                       // Initialize crossbar and GPIO
   PCA0_Init ();
   ADC0_Init();

   EA = 1;                             // enable global interrupts

   while (1)
   {
      x = avgVin();                    // get avg. ADC reading
      x *= HTSPAN;                     // multiply by span
      y = x>>8;                        // through away low byte
      y += LATENCY;                    // add minimum latency
      EIE1 &= ~0x08;                   // disable PCA interrupt
      HiTime =  y;                     // coherent update of global hitime
      EIE1    |= 0x08;                 // enable PCA interrupt
   }
}

//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------

void SYSCLK_Init (void)
{
   OSCICN = 0x07;                      // configure for 24.5 MHz
   RSTSRC = 0x04;                      // enable missing clock detector
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports.
// P0.0 - PWM - CEX0 - push-pull output
// P0.1 -
// P0.2 -
// P0.3 -
// P0.4 -
// P0.5 -
// P0.6 - Analog Input
// P0.7 -
//
void PORT_Init (void)
{
   XBR0     =  0x00;                   // skip nothing
   XBR1     =  0x40;                   // Enable CEX0 on P0.0
   P0MDOUT  =  0x01;                   // enable CEX0 as a push-pull output
   P0MDIN   = ~0x40;                   // enable ADC input on P0.6
   XBR2    |=  0x40;                   // enable crossbar

}

//-----------------------------------------------------------------------------
// PCA0_Init
//-----------------------------------------------------------------------------

void PCA0_Init (void)
{
   udblbyte output;

   PCA0MD   = 0x08;                    // PCA uses sysclk, no CF int
   PCA0CPM0 = 0x4D;                    // High Speed Output Mode, enable ECCF0
   PCA0L    = 0x00;                    // reset the timer
   PCA0H    = 0x00;
   output.w = PERIOD/2;                // schedule first interrupt
   PCA0CPL0 = output.b.lo;
   PCA0CPH0 = output.b.hi;
   NextEdge = PERIOD;                  // initialize NextEdge
   EIE1    |= 0x08;                    // enable PCA0 interrupts
   EIP1    |= 0x08;                    // set PCA to high priority

   CR = 1;                             // start PCA0 timer
}

//-----------------------------------------------------------------------------
// PCA0_ISR
//-----------------------------------------------------------------------------
void PCA0_ISR (void) interrupt 9 using 1
{
   static bit cycle = 0;
   udblbyte output;
   
   output.w = NextEdge;
   PCA0CPL0 = output.b.lo;             // write lo byte first
   PCA0CPH0 = output.b.hi;             // write hi byte second
   PCA0CN &= ~0x87;                    // clear all PCA flags
   if (cycle)
      {
      NextEdge += PERIOD;
      NextEdge -= HiTime;
      }
   else
   {
      NextEdge += HiTime;
   }
   cycle = !cycle;
}


//-----------------------------------------------------------------------------
// ADC functions
//-----------------------------------------------------------------------------

void ADC0_Init (void)
{
   ADC0CN = 0x00;                      // normal tracking mode;
                                       // ADC0 conversions are initiated
                                       // on writes to AD0BUSY;
   AMX0SL =  0xf6;                     // select P0.6
   ADC0CF =  0x81 ;                    // AD0SC=4 gain =1
   REF0CN =  0x0a;                     // ADC uses Vdd for full scale
   EIE1  &= ~0x04;                     // disable ADC0 EOC interrupt
   AD0EN  =  1;                        // enable ADC
}

unsigned char readVin(void)
{
   AD0INT = 0;                         // clear ADC0 end-of-conversion
   AD0BUSY = 1;                        // initiate conversion
   while (!AD0INT);                    // wait for conversion to complete
   return ADC0;
}

unsigned char avgVin(void)
{
   unsigned char i, result;
   unsigned int sum;

   sum = 0;
   for (i = 64; i != 0; i--)           // repeat 64 times
   {
      sum += readVin();                // read ADC and add to sum
   }
   result = (unsigned char)(sum>>6);   // divide by 64 and cast to uchar
   return result;                      // return average reading
}