www.pudn.com > avrepp.zip > hostepp.c

/**** A P P L I C A T I O N   N O T E   A V R 3 2 5 ************************ 
 * 
 * Title:          High-speed Interface to Host EPP Parallel Port 
 * Version:        1.0 
 * Last updated:   2001.12.20 
 * Target:         All AVR Devices with 12 I/O pins or more 
 * 
 * Support E-mail: avr@atmel.com 
 *  
 * DESCRIPTION 
 * This Application Note describes a method for high-speed bidirectional data 
 * transfer between an AVR microcontroller and an off-the-shelf Intel x86 
 * desktop computer. 
 * 
 * This host program is constructed to talk to an AVR running AVREPP (over  
 * an EPP link). 
 * 
 * It functions more or less as a terminal program, passing keyboard data  
 * into the AVR, and displaying data from the AVR on the screen. The program  
 * exits if ESC (0x1b) is typed. 
 * 
 * This program expects the EPP to be at LPT1 (0x378); to change this, change  
 * PPORT below.  
 * 
 * This program was written for DOS Turbo-C 2.01 
 ***************************************************************************/ 
 
#include                 /* inp, outp                               */ 
#include               /* kbhit() et al                           */ 
 
#define PPORT   0x378           /* LPT1                                    */ 
 
#define EPPSTAT(_p) ((_p)+1)    /* EPP/SPP status register                 */ 
#define EPPDATA(_p) ((_p)+4)    /* EPP data register                       */ 
#define SPPCTL(_p)  ((_p)+2)    /* SPP Control Register                    */ 
 
/* 
 *      status register bits 
 */ 
#define	EPPTIMEOUT 0x01 
#define EPPBSY     0x80 
#define	EPPINTR	   0x40 
#define EPPINIT    0x04         /* 0bxxxx0100                             */ 
 
#define ESC        0x1B         /* use this to quit                       */ 
 
int main(int argc, char *argv[]) 
{ 
 
    unsigned char c, r; 
 
    if (argc || argv)           /* ARGSUSED                               */ 
        ; 
 
    outp(SPPCTL(PPORT), EPPINIT);      /* FAMcK                           */ 
 
    /* Forever (or at least until user types Esc):                        */ 
 
    while (1)  
    { 
 
        /* Check keyboard side                                            */ 
 
        if (kbhit())  
        { 
            /* Something typed -- pass it through                         */ 
 
            c = getch();           /* get what user typed                 */ 
            if (c == ESC)          /* way-out                             */ 
	        break; 
            outp(EPPDATA(PPORT), c);	/* write to port */ 
        } 
 
        /* Check EPP (Rx) side. The EPP peripheral (the AVR) indicates    */ 
        /* that data is ready via the INTR signal.                        */ 
 
        r = inp(EPPSTAT(PPORT)); 
 
        if ((r & EPPBSY) == 0)      /* powered down?                      */ 
            continue;               /* ignore it                          */ 
 
        if (r & EPPINTR)            /* intr is request to read            */  
        {		 
            c = inp(EPPDATA(PPORT));	/* so do it		          */ 
            r = inp(EPPSTAT(PPORT));	/* get the status register        */ 
 
            /* If we're following the protocol (reading only on EPPINTR)  */ 
            /* we should Never see a timeout.                             */ 
 
            if (r & EPPTIMEOUT)  
            { 
                outp(EPPSTAT(PPORT), EPPTIMEOUT); /* clear it             */ 
                c = '@';                        /* display '@' on timeout */ 
            } 
            putch(c);                           /* display on the screen  */ 
        } 
    } /* end while(1)                                                     */ 
 
    return(0); 
}