;**********************************************************************
;
; LISTING 1 - THE DURATION BETWEEN TWO MEASUREMENTS
;
; ﾒNovel idea implements low-cost keyboard,ﾓ 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
} |
