TinyTxt - a minimal text interpreter based on Ward Cunningham's Txtzyme

TinyTxt_UART_1.ino

// TinyTxt_UART_1

// Ken Boak  January 2016

// Based on  Ward Cunningham's Txtzyme interpreter

// This is the cut down kernel with UART support - compiles to 658 bytes

// Lacking all features except  p  (print x)

// Additional features must be added as case statements in textEval()

#include <stdio.h>
#include <stdlib.h>
#include <avr/io.h>

// MACRO for a 62.5nS  delay 
#define NOP __asm__ __volatile__ ("nop\n\t")

// and then use it in code as follows
 NOP; // delay 62.5ns on a 16MHz AtMega


#define F_CPU 16000000UL        // define the clock frequency as 16MHz
#define BAUD 115200

#include <util/setbaud.h>       // Set up the Uart baud rate generator
#include <uart.h>

unsigned int x = 0;
int d = 6;                      // On WiNode set LED pin as 6
int i,  j, w,  y, z ;

main() {
  
  uart_init();                       // Enable UART
  DDRD = DDRD | B11111100;           // Sets pins 2 to 7 as outputs without changing the value of pins 0 & 1, which are RX & TX
  DDRB = DDRB | B11111111;           // Port B (Pin 9 - 13) is also output
//  PORTB &= B11111110;              // Set pin 8 low 
  OK();
  
  while(1){
  
  char buf[64];
  textRead(buf, 64);
  textEval(buf);
}

}

void textRead (char *p, byte n) {
  byte i = 0;
  while (i < (n-1)) {
//    while (!Serial.available());
    char ch = u_getchar();
    if (ch == '\r' || ch == '\n') break;
    if (ch >= ' ' && ch <= '~') {
      *p++ = ch;
      i++;
    }
  }
  *p = 0;
}

void textEval (char *buf) {
  unsigned int k = 0; 
  char *loop;
  char ch;
  while ((ch = *buf++)) {
    switch (ch) {
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      x = ch - '0';
      while (*buf >= '0' && *buf <= '9') {
        x = x*10 + (*buf++ - '0');
      }
      break;
      
      
    case 'p':
    printlong(x);
    crlf();
    break;
    
    
    case '*':
//    x=x*y;
    break;
    
 
    }
  }
}

//--------------------------------------------------------------------------------------
// UART Routines
//--------------------------------------------------------------------------------------

void uart_init(void) 
{
    UBRR0H = UBRRH_VALUE;
    UBRR0L = UBRRL_VALUE;
    UCSR0A |= _BV(U2X0);
    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00);       // 8-bit data 
    UCSR0B = _BV(RXEN0) | _BV(TXEN0);         // Enable RX and TX
}

void u_putchar(char c) {
    loop_until_bit_is_set(UCSR0A, UDRE0);     // Wait until data register empty
    UDR0 = c;
}

char u_getchar(void) {
    loop_until_bit_is_set(UCSR0A, RXC0);       // Wait until data exists
    return UDR0;
}

//-----------------------------------------------------------------------------------------
// Print a 16 bit int number 

// Put a Number
static void printlong(unsigned short num) {
  if (num / (unsigned short)10 != 0) printlong(num / (unsigned short)10);
  u_putchar((char)(num % (unsigned short)10) + '0');
   
  return;
}

//----------------------------------------------------------------------------------------------------------  
// Print a string
void printstring(char *buf)
{
  
}
  
//---------------------------------------------------------------------------------------------------------- 
// Print a CR-LF

  void crlf(void)                  // send a crlf 
  {  
  u_putchar(10);
  u_putchar(13); 
  }

 //---------------------------------------------------------------------------------------------------------
 
 // Print OK

  void OK(void)                  // send OK crlf
  {  
  u_putchar('O');
  u_putchar('K'); 
  u_putchar(10);
  u_putchar(13); 
  }
 //---------------------------------------------------------------------------------------------------------
 // Generate a multiple uS delay
 
 void delay_uS(int w)
  {
  int k;
  for(k = 0; k <= w; k++)
  {  
   
   /*
   
   NOP;
   NOP;
   */
   NOP;
 }  
 
 
 }
 
 //---------------------------------------------------------------------------------------------------------
 
 void delay_mS(int z)
 
 {     
   for(j = 0; j <= z; j++)   
   {
    delay_uS(1000);                 // 1000 us delay
   }  
 }
 
 
 
//------------------------------------That's All Folks!-------------------------------------