f_10_12_txfifo.c

* Use 10 MHz crystal frequency. * Use Timer0 for ten millisecond looptime. * Blink "Alive" LED e

// In Hyperterminal, use File->Properties->Settings->AscII setup
// and ensure that line delay and character delay are 0 milliseconds


#include "config.h"

#include "math.h"  // for sqrt function

#include "serial.c"

/* 

'getch' uses interrupt driven input to read the values from
the serial port.

'putch' also uses interrupt driven IO

This program reads decimal number, computers the 
floating point square root, and prints it out.

Will be used to illustrate buffering in interrupt driven
input 
*/

char getch (void);
void putch (char c);
void pcrlf (void);
char getche (void);


#define BUFMAX 32


volatile unsigned char txbuf[BUFMAX];
volatile unsigned char txhead, txtail;

void putch (char c)
{
  char tmp;

  // must use tmp because we do not want ISR thinking
  // that buffer is empty
  tmp = txhead;
  tmp++;
  if (tmp == BUFMAX) tmp = 0;
  while(tmp == txtail);  // wait until buffer empties
  txbuf[tmp] = c;
  txhead = tmp;
  // enable interrupt
  TXIE = 1;
}


void pcrlf (void)
{
  putch(0x0a);
  putch(0x0d);
}

// head points to last character received 
volatile unsigned char ibuf[BUFMAX];
volatile unsigned char head, tail;

// return 8 bit char from Recieve port 
// interrupt driven version 
char getch (void)
{
  unsigned char c;

  while (head == tail) {};
  tail = tail + 1;
  if (tail == BUFMAX) tail = 0;
  c = ibuf[tail];
  return(c);
}

// needed by scanf library call, 
// get character and echo
char getche (void)
{
  unsigned char c;
  c = getch();
  putch(c);
  return(c);
}

#if defined(__18CXX)
void my_gets (char *s);
//return a string from the console
void my_gets (char *s){
 char c;
 
 do {
  c = getche();
  *s = c;
  s++;
  } while (c != '\r');
}
#endif

#if defined(HI_TECH_C)
void interrupt pic_isr(void)
#endif
#if defined(__18CXX)
#pragma interrupt pic_isr
void pic_isr(void)
#endif
{
  // see if this interrupt was generated by a receive character 
  if (RCIF) {  // check RCIF bit 
    head = head + 1;
    if (head == BUFMAX) head = 0;
    // reading this register clears interrupt bit 
    ibuf[head] = RCREG;  
  }
  if (TXIF) {  //check TXIF bit
    if (txtail == txhead) { // buffer is empty, disable
      TXIE = 0;
    } else {
      // get character
      txtail = txtail + 1;
      if (txtail == BUFMAX) txtail = 0;
      TXREG = txbuf[txtail];
    }
  }
}

unsigned ivalue,root;
double temp_fp, root_fp;

void main(void)
{
  // 19200 in HSPLL mode, crystal = 7.3728 MHz 
  serial_init(95,1); 
  // enable received character interrupt
  IPEN = 0;    RCIE = 1;    PEIE = 1;   GIE = 1;  
  printf("Has software tx/rx fifo buffer.");  pcrlf();
  printf("Hit any key to start...");  pcrlf();
  getch();
  while(1) {
  // read an ASCII string in, convert to decimal
#if defined(HI_TECH_C)
    scanf("%d",&ivalue); 
#endif
#if defined(__18CXX)
    {// MCC18 does not have scanf, just get string from console, use atoi
	  char buf[30];
	  my_gets(buf);  // get a string from console
	  ivalue = atoi(buf);  // convert string to integer
	}
#endif    
    // convert integer to floating point value
    temp_fp = ivalue; 
    // use library routine to compute floating point square root
    root_fp = sqrt(temp_fp); 
    root = (unsigned int)root_fp;  // integer square root
    printf("Square root of %d is: %d",ivalue,root); pcrlf();
  }
}

//for MCC18, place the interrupt vector goto
#if defined(__18CXX)
#if defined(HIGH_INTERRUPT)
#pragma code HighVector=HIGH_INTERRUPT
#else
#pragma code HighVector=0x0008  
#endif
void HighVector (void)
{
    _asm goto pic_isr _endasm
}
#pragma code
#endif