Re: C Programming

Chris Michalak (cmich@CAM.ORG) Sat, 2 Dec 2000 03:35:35 -0500 (EST) 

Date: Sat, 2 Dec 2000 03:35:35 -0500 (EST)
From: Chris Michalak <cmich@CAM.ORG>
Subject: Re: C Programming




William,

Here is my rdkbd function, using a loops. Let me know if something is
unclear.

int rdkbd (void)
/* waits for all keys on keypad to be released. Then waits for a key to be
pressed and returns it's integer value */
{
  int dat;  /* used to store raw input data */
  int i,j;  /* loop variables */
  spoke(DATA_PORT,0xF);      /* check all rows */
  while ( speek(DATA_PORT) & 0xF ) { };  /* wait for all keys to be
cleared */
  while ( !(speek(DATA_PORT) & 0xF)) { } ;  /* waits for a keypress */
  for (i=0;i<=3;i++) {                   /* for each row */
    spoke(DATA_PORT,1<<i);
    if (dat = speek(DATA_PORT) & 0xF) {  /* true if a key in this row */
      for (j=0;j<=3;j++) {                /* for each colum */
        if ((dat>>j) & 1) { return (j*4+i); }  /* found it */
      }
    }
  }
}


Chris Michalak

On Fri, 1 Dec 2000, William Tse wrote:

> I was study today and was trying to use some loops to
> write the read keyboard part of the program of lab #2
> instead of using 16 "if" statements and I could not
> get it to work.  Can someone help, with an example
> perhaps?
> 
> William Tse
> 
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