di3155.txt
;*********************************************************************************
;
; LISTING 1 - THE DURATION BETWEEN TWO MEASUREMENTS
;
; "Novel idea implements low-cost keyboard," EDN, April 3, 2002, pg 69
;
;*********************************************************************************

/*
 * Function :	LittleKb_Scan with 1 I/O
 *
 * Description :	scans the Little Keyboard
 *
 * Return value :	0 if not any touch is pushed
 *			else a value between 1 and 255
 *
 * Note : 		by default, KB_IO is an output
 *			and its exit is set to 0 (see Note 1)
 */

BYTE LittleKb_Scan (void)
{
BYTE bRet = 0;
				// beginning …
KB_IO = 1;			// sets I/O (out) to 1 (see Note 1)
Delay_us(55); 			// waits for 55us (see Note 1)

KB_IO_Input();			// KB_IO is an input
do
{
	bRet++;			// counter ++
	if(KB_IO == 0)		// checks I/O (input)
		break;
} while (bRet != 0);		// the loop lasts 2us

KB_IO = 0;			// resets I/O to 0 (see Note 1)
KB_IO_Output();			// KB_IO is an Output
				// and discharges C
return bRet; 			// … end
}