example_8_qdec.c

CYGNAL单片机

//-----------------------------------------------------------------------------
// Example 8
// Quadrature Decode
//-----------------------------------------------------------------------------
// Copyright 2004 Silicon Laboratories Inc.
//
// AUTH: KAB
// DATE: 12MAR04
//
// This example provides a quadrature decode interface using the
// external interrupts INT0 and INT1. The external interrupts are
// assigned to P0.0 and P0.1.
//
// The interrupt service routines first complement the appropriate
// interrupt polarity bit and then increment or decrement the global
// variable Position as needed. A nested if...else statement is used
// to determine the appropriate action depending on the status of
// the  polarity bits.
//
// The Position variable is output on the UART each time the Position
// changes. The Position can be monitored using a standard Terminal
// application such as Hyperterm. The Terminal should be configured
// for 9600 bps.
//
// Target: C8051F30x
//
// Tool chain: KEIL Eval 'c'
//
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051f300.h>                 // sfr declarations
#include <stdio.h>                     // printf()
//-----------------------------------------------------------------------------
// Macros
//-----------------------------------------------------------------------------

#define SYSCLK       24500000          // sysclk frequency in Hz
#define BAUDRATE     9600              // baud rate of UART in bps

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

void main (void);
void SYSCLK_Init (void);
void PORT_Init (void);
void UART0_Init (void);
void EINT_Init (void);
void INT0_ISR (void);
void INT1_ISR (void);

//-----------------------------------------------------------------------------
// Global VARIABLES
//-----------------------------------------------------------------------------
unsigned int Position;                 // position of quadrature encoder
sbit CHA = P0^0;                       // quadrature channel A pin state
sbit CHB = P0^1;                       // quadrature channel B pin state
//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------

void main (void)
{

   unsigned int p;                     // last position

   PCA0MD = 0x00;                      // disable watchdog timer

   PORT_Init ();                       // initialize GPIO and Crossbar
   SYSCLK_Init ();                     // initialize System Clock
   EINT_Init();                        // initialize External Interrupt
   UART0_Init ();                      // initialize UART

   Position = 0;                       // clear initial position

   EA = 1;                             // enable global interrupts

   while (1)
   {
      while(p == Position);            // do nothing until moved

      p = Position;                    // update p

      printf("%u     \r", p);          // display position
   }
}

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

//-----------------------------------------------------------------------------
// 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 - INT0 - CHA input
// P0.1 - INT1 - CHB input
// P0.2 -
// P0.3 -
// P0.4 - UART TX - push-pull output
// P0.5 - UART RX
// P0.6 -
// P0.7 - C2D
//
void PORT_Init (void)
{
   XBR0    =  0x03;                    // skip P0.0 & P0.1
   XBR1    =  0x03;                    // enable uart
   P0MDOUT =  0x10;                    // TX output
   XBR2   |=  0x40;                    // enable crossbars

}

//-----------------------------------------------------------------------------
// EINT_Init
//-----------------------------------------------------------------------------
void EINT_Init (void)
{
    IT01CF  =  0x10;                   // INT0=P0.0, INT1=P0.1
    if(CHA==0)                         // check CHA state
      IT01CF|=0x08;                    // if low, trigger high
    if(CHB==0)                         // check CHB state
      IT01CF|=0x80;                    // if low, trigger high
    TCON   |=  0x05;                   // set IT0 & IT1 for edge trigger
    TCON   &= ~0x0a;                   // clear IE0 and IE1 flags
    IP     |=  0x05;                   // INT0 and INT1 high priority
    IE     |=  0x05;                   // Enable INT0 and INT1

 }

//-----------------------------------------------------------------------------
// INT0_ISR, INT1_ISR
//-----------------------------------------------------------------------------
//
// These two interrupt service routines occur when the respective encoder
// channel changes state. The interrupt service routines are identical
// except for the respective change in the interrupt flag, polarity bit, and
// count direction. The nested if...else statement performs the logical
// equivalent of an exclusive OR function using the polarity bits as the
// quadrature state.
//
void INT0_ISR (void) interrupt 0
{

   IT01CF ^= 0x08;                     // toggle edge select trigger


   if ((IT01CF&0x08)==0x08)
      if((IT01CF&0x80)==0x80)
         Position--;                   // if both decrement
      else
         Position++;                   // if different increment
   else
      if((IT01CF&0x80)==0x80)
         Position++;                   // if different increment
      else
         Position--;                   // if neither decrement
}

void INT1_ISR (void) interrupt 2
{

   IT01CF ^= 0x80;                     // toggle edge  select trigger

   if ((IT01CF&0x08)==0x08)
      if((IT01CF&0x80)==0x80)
         Position++;                   // if both increment
      else
         Position--;                   // if different decrement
   else
      if((IT01CF&0x80)==0x80)
         Position--;                   // if different decrement
      else
         Position++;                   // if neither increment
}

//-----------------------------------------------------------------------------
// UART0_Init
//-----------------------------------------------------------------------------
//
// Standard UART0 Init from software examples
//
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 &= ~0x13;                  // T1M = 0; SCA1:0 = 01
      CKCON |=  0x01;
   } 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 &= ~0x13;                  // T1M = 0; SCA1:0 = 10
      CKCON |=  0x02;
   }

   TL1 = TH1;                          // init Timer1
   TMOD &= ~0xf0;                      // TMOD: timer 1 in 8-bit auto-reload
   TMOD |=  0x20;
   TR1 = 1;                            // START Timer1
   TI0 = 1;                            // Indicate TX0 ready
}