/* PRINTER port output examples */ #include #include /*inport, outport, delay function used.*/ #include /*cursor control*/ /* main function prototypes */ /* INITIALISATION */ void init_screen(); void find_port(); void port_address(); void init_port(); /* TOPMENU */ void main_menu(); void main_menu_choice(); /* STATUS REGISTER ROUTINES */ void status(); void power_switches(); /* CONTROL REGISTER ROUTINES */ void control(); /* DATA REGISTER ROUTINES */ void data(); void sub_menu(); void sub_menu_option(); void initial_data_out(); void data_out(); /* embedded function prototypes */ void up(); void down(); void left(); void right(); void finish(); void terminate(); char get_menu_option(); /* global variables */ typedef unsigned int WORD; int data_reg,status_reg,cont_reg; unsigned char init_val=0x00; /* set initial value to 0 and limit values to 0->255 only */ main() { /* local variable */ char choice; /* INITIALISE SYSTEM */ init_screen(); find_port(); port_address(); init_port(); /* TOP MENU */ main_menu(); { do { choice = get_menu_option(); if (choice == 'S') { status(); } if (choice == 'O') { data(); } if (choice == 'C') { control(); } } while (choice != 'Q'); terminate(); /* programme ends here */ } return; } /******************************* INITIALISATION **************************/ void init_screen() /* initialise screen */ { clrscr(); /* of any previous rubbish */ _setcursortype(_NOCURSOR); /* temporarily remove cursor */ } void find_port() /* find out the address of the printer port */ { /**************************************************** * THIS FUNCTION READS THE BIOS ADDRESS 0040h WITH AN * OFFSET OF 08h TO OBTAIN THE ADDRESS OF LPT_1. ****************************************************/ data_reg = *(WORD far *) MK_FP (0x0040,0x08); status_reg = data_reg + 1; cont_reg = data_reg + 2; } void port_address() /* print port address on screen */ { printf("\t\t\tdata register is at address: %0Xh\n", data_reg); printf("\t\t\tstatus register is at address: %0Xh\n", status_reg); printf("\t\t\tcontrol register is at address: %0Xh\n", cont_reg); } void init_port() /* initialise printer port */ { /* output data */ outportb(data_reg,init_val); outportb(cont_reg,0x0b); /* turn all outputs off */ } /***************************** end of INITIALISATION **********************/ /******************************* TOPMENU **********************************/ void main_menu() /* print menu options on screen */ { /* position start of menu */ /* print menu */ printf("\n\n\n"); printf("\t\t ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»\n"); printf("\t\t º º\n"); printf("\t\t º MAIN MENU º\n"); printf("\t\t º º\n"); printf("\t\t º enter S to read Status register º\n"); printf("\t\t º º\n"); printf("\t\t º enter O to write to data register º\n"); printf("\t\t º º\n"); printf("\t\t º enter C to write to Control register º\n"); printf("\t\t º º\n"); printf("\t\t º enter Q to Quit the programme º\n"); printf("\t\t º º\n"); printf("\t\t ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ\n\n"); } /************************** end of TOPMENU *******************************/ /********************* STATUS REGISTER ROUTINES **************************/ void status() /* Routine that reads the switch inputs (via the STATUS register) that are connected to the parallel port */ { /* local variables */ unsigned char raw_data,corrected_data,switches; while (!kbhit()) /* do all of the following until a key is pressed */ { clrscr(); printf("\n\n\n\t\t\t PRESS ANY KEY TO QUIT ROUTINE"); power_switches(); /* provide power for the switches */ /***************************************************** PARALLEL PORT STATUS REGISTER d7 = /BUSY pin 11 *inverted* d6 = /ACKNOWLEDGE pin 10 d5 = PAPER OUT pin 12 d4 = SELECT pin 13 d3 = /ERROR pin 14 d2 = unconfigured not used d1 = unconfigured not used d0 = unconfigured not used *****************************************************/ /* read Status register and shift right 3 times */ /* inputs can now be read on d0 to d4 */ raw_data = inportb(status_reg) >> 3; /* mask off bit d4 and invert its value to correct polarity */ corrected_data = (~raw_data & 0X10); /* NOW COMES THE CLEVER BIT! The upper nibble has been masked off, d4 inverted and equated to corrected_data. The lower nibble now needs to be masked off to dump the upper nibble. The upper and lower nibbles are now added together and equated to switches. */ switches = (corrected_data | (raw_data & 0X0f)); printf("\n\n\n\t\t\t Status Register = % .02X\r",switches); delay(200); /* switch debounce */ } finish(); return; } void power_switches() /* set the /select in (D3 in control register) to provide power for the switches */ { /* output data */ outportb(cont_reg,0x03); } /****************** end of STATUS REGISTER ROUTINES ***********************/ /******************** DATA REGISTER ROUTINES ******************************/ void data() { /* local variable */ char choice; clrscr(); sub_menu(); initial_data_out(); sub_menu_option(); } void sub_menu() /* print menu options on screen */ { /* position start of menu */ /* print menu */ printf("\n\n\n"); printf("\t\t ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»\n"); printf("\t\t º º\n"); printf("\t\t º DATA REGISTER MENU º\n"); printf("\t\t º º\n"); printf("\t\t º enter L to shift a single bit Left º\n"); printf("\t\t º º\n"); printf("\t\t º enter R to shift a single bit Right º\n"); printf("\t\t º º\n"); printf("\t\t º enter U to increment binary count Up º\n"); printf("\t\t º º\n"); printf("\t\t º enter D to decrement binary count Down º\n"); printf("\t\t º º\n"); printf("\t\t º enter Q to Quit º\n"); printf("\t\t º º\n"); printf("\t\t ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ\n\n"); } void initial_data_out() { /* print the value of the data register on screen */ printf("\n\t\t\t initial output state = % 02X",init_val); } void sub_menu_option() /* get the required MENU option */ { /* local variable */ char choice; do { choice = get_menu_option(); if (choice == 'U') { up(); } if (choice == 'D') { down(); } if (choice == 'L') { left(); } if (choice == 'R') { right(); } data_out(); } while (choice != 'Q'); /* program returns to main menu */ finish(); } void up() /* increment output by one upto FFh and stop */ { /* set upper limit */ if (init_val <= 0xFE) { init_val++; } /* if already at upper limit dont go any further */ else { init_val = 0xFF; } } void down() /* decrement output down by one to 00h and stop */ { /* set lower limit */ if (init_val >= 1) { init_val--; } /* if already at lower limit dont go any further */ else { init_val = 0; } } void left() /* shift left a single bit upto 80h and stop */ { /* set start condition by preloading the lsb */ if(init_val == 0) { init_val++; } /* shift left */ else { init_val <<= 1; } } void right() /* shift right a single bit down to 00h. no need to stop as bits are 'lost'as there is no rotate through carry !! */ { init_val >>=1; } void data_out() { printf("\r\t\t\t current output state = % .02X",init_val); outportb(data_reg,init_val); } /****************** end of DATA REGISTER ROUTINES ************************/ /******************* CONTROL REGISTER ROUTINES ***************************/ void control() /* Exercises the LED's attached to the printer port via the CONTROL register */ { /* initialise outputs */ outportb(cont_reg,0x0b); /* switch all outputs off */ clrscr(); printf("\n\n\n\t\t\t PRESS ANY KEY TO QUIT ROUTINE"); delay(1000); while (!kbhit()) /* do all of the following until a keypress */ { /******************************************************** PARALLEL PORT CONTROL REGISTER d7 = unconfigured not used d6 = unconfigured not used d5 = DIRECTION CONTROL not used d4 = IRQ ENABLE not used d3 = /SELECT IN pin 17 (inverted) d2 = /INITIALISE pin 16 (inverted) d1 = /AUTOFEED pin 14 d0 = /STROBE pin 1 (inverted) ********************************************************/ /* output following bit pattern to cycle leds NOTE: cannot use a for loop as the required bit pattern is not contiguous 0x0a strobe on (inverted) 0x09 autofeed on (inverted) 0x0f initialise on 0x03 select-in on (inverted) 0x0b all outputs off */ { /* shift left */ outportb(cont_reg,0x0a); /* strobe on */ delay(1000); outportb(cont_reg,0x09); /* autofeed on */ delay(1000); outportb(cont_reg,0x0f); /* initialise on */ delay(1000); outportb(cont_reg,0x03); /* select-in on */ delay(1000); /* shift right */ outportb(cont_reg,0x0f); /* initialise on */ delay(1000); outportb(cont_reg,0x09); /* autofeed on */ delay(1000); } } finish(); return; } /******************* end of CONTROL REGISTER ROUTINES ********************/ /********************* embedded functions ********************************/ char get_menu_option() /* This routine returns the value of menu selected option */ { char choice; /* using getch() does not echo choice to screen, also using toupper makes the case of the keyboard insensitive */ choice = toupper(getch()); return(choice); } void finish() /* reset printer port and clear current menu option data from screen */ { outportb(data_reg,0x00); outportb(cont_reg,0x0b); clrscr(); main_menu(); } void terminate() /* reset printer port and clear all program data from screen */ { clrscr(); _setcursortype(_NORMALCURSOR); exit(1); } /************************ END OF PROGRAMME *******************************/