lad_pad.h

Linux嵌入式设计配套光盘,学习嵌入式设计可参考

/*
 * An LCD/keypad interface.
 *
 * The book "Linux Appliance Design" describes a simple LCD and
 * keypad interface.  This file documents the defines and the
 * API of that interface.
 *
 * Copyright (c) 2005,2006 by Laddie Group, Inc
 *
 */

/***************************************************************************
 * LICENSE:
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 ***************************************************************************/


#ifndef LADPAD_H
#define LADPAD_H


/* CONTENTS:
 - Overview
 - Hardware
 - Installation
 - Usage
 - Defines
 */

/* -OVERVIEW
The book "Linux Appliance Design" includes a sample appliance,
called "Laddie".  The sample appliance is an alarm system that
uses the five input pins on a parallel port as inputs from the
alarm system hardware.  The sample appliance includes a web
interface, a command line interface, a framebuffer and LIRC
interface, a MIB and SNMP agent, and a LCD/keypad interface.
This file describes the LCD/keypad interface by describing its
hardware, installation, usage, and API.
*/


/* -HARDWARE
The Laddie appliance is an alarm system with a remote station
that allows a user to enable or disable the alarm system.  This
"remote station" has a two line display, a sixteen button keypad,
and an LED.  This section briefly describes the hardware for the
remote station.  Please see http://www.linuxappliancedesign.com
for the full schematics or, better, buy the book.

The hardware can be thought of as having three sections, two
output sections and one input section.  The ouput sections are
the two line alphanumeric display and the LED.  The input section
is the 16 button keypad.  We use a standard parallel port for
all IO to the device.  

The LCD display uses an HD44780 compatible controller.  This is
by far the most widely used text LCD controller and the code given
here should port easily to any 44780 based device.  A complete
description of these types of displays is beyond the scope of this
document and the interested reader is referred to the following
web sites for more information:
   http://www.myke.com/lcd.htm
   http://home.iae.nl/users/pouweha/lcd/lcd.shtml
*/


/* -INSTALLATION
You must build the ladpad module and to do this you should have
the Linux kernel source code installed on your development system.
Download the ladpad module source code from the LAD web site and
install in your /usr/src/linux (or equivalent) directory.  Build 
and install the module with:
   cd /usr/src/linux
   tar -xzf ladpad.tgz
   cd ladpad
   make

The major number is assigned automatically.  Look in /proc/devices
for the number assigned.
   LADPAD_MAJOR=`grep ladpad /proc/devices | awk '{print $1}'`
   mknod /dev/ladpad c $LADPAD_MAJOR 0

You may wish to place the above lines in your rc.local file.

After you have installed the ladpad module and created the ladpad
device you can read from its keypad and write to its LCD and LED.
Verify that keypad is connected and working with the following
command:
   cat /dev/ladpad

Keys pressed on the keypad should be displayed in your terminal
window.

Verify that output to the display is working with the following
command:
   echo -n "Hello World" > /dev/ladpad

Verify that the LED is working with the following:
   echo -ne '\021' >/dev/ladpad 
   echo -ne '\003' >/dev/ladpad 
*/


/* -USAGE
Input from the kepad is straighforward.  Reading from the device
will block until the user presses a key.  When a key is presses,
the device driver will return the ASCII value of the key pressed.
You can use either blocking reads or a select statement to wait
for key presses.

Output to the LCD is a little more complicated in that the 44780
type of displays have a command set that allows defining the font
for custom characters and allows cursor positioning.  You can
transparently send commands to the LCD by prepending the command
with an escape character.

CHARACTER  RESPONSE
printable  Puts the character on the display at the current cursor
           location.  The cursor is then shifted one position to 
           the right.  You can override the "shift right" default
           by sending the appropriate command to the LCD.
0x10       Escape character for LCD commands.  The next byte read is
           sent to the LCD display as a command.  For example, the
           two byte sequence to move the cursor to the beginning of
           the first line is: 0x10, 0x80.  To move to the beginning
           of the second line: 0x10, 0xC0.  Any 8 bit pattern can be
           used in the second byte, and the data is transparently
           delivered to the LCD as a command.  You can use this 
           escape mechanism to define custom characters if you wish.
0x11       Escape character for LED control.  The next byte read 
           has the desired state of the LED.  Zero is off, 0xFF is
           on steady, and any other value is the number of jiffies
           between transitions.
*/



/* -DEFINES
*/

#define LADPAD_CMD  ((char) 0x10)
#define LADPAD_LED  ((char) 0x11)


#endif  /* LADPAD_H */