Dependencies:   mbed

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API Documentation at this revision

Comitter:
simon
Date:
Tue Nov 17 10:16:30 2009 +0000
Commit message:

Changed in this revision

TextLCD.cpp Show annotated file Show diff for this revision Revisions of this file
TextLCD.h Show annotated file Show diff for this revision Revisions of this file
main.cpp Show annotated file Show diff for this revision Revisions of this file
mbed.bld Show annotated file Show diff for this revision Revisions of this file
diff -r 000000000000 -r b77078f30b97 TextLCD.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TextLCD.cpp	Tue Nov 17 10:16:30 2009 +0000
@@ -0,0 +1,153 @@
+/* mbed TextLCD Library
+ * Copyright (c) 2007-2009 sford
+ * Released under the MIT License: http://mbed.org/license/mit
+ *
+ * TODO: Needs serious rework/neatening up!
+ */
+ 
+#include "TextLCD.h"
+
+#include "mbed.h"
+#include "error.h"
+
+using namespace mbed;
+
+/*
+ * useful info found at http://www.a-netz.de/lcd.en.php
+ *
+ *
+ * Initialisation
+ * ==============
+ *
+ * After attaching the supply voltage/after a reset, the display needs to be brought in to a defined state
+ *
+ * - wait approximately 15 ms so the display is ready to execute commands
+ * - Execute the command 0x30 ("Display Settings") three times (wait 1,64ms after each command, the busy flag cannot be queried now). 
+ * - The display is in 8 bit mode, so if you have only connected 4 data pins you should only transmit the higher nibble of each command.
+ * - If you want to use the 4 bit mode, now you can execute the command to switch over to this mode now.
+ * - Execute the "clear display" command
+ *
+ * Timing
+ * ======
+ *
+ * Nearly all commands transmitted to the display need 40us for execution. 
+ * Exceptions are the commands "Clear Display and Reset" and "Set Cursor to Start Position" 
+ * These commands need 1.64ms for execution. These timings are valid for all displays working with an 
+ * internal clock of 250kHz. But I do not know any displays that use other frequencies. Any time you 
+ * can use the busy flag to test if the display is ready to accept the next command.
+ * 
+ * _e is kept high apart from calling clock
+ * _rw is kept 0 (write) apart from actions that uyse it differently
+ * _rs is set by the data/command writes
+ */
+
+TextLCD::TextLCD(PinName rs, PinName rw, PinName e, PinName d0, PinName d1, 
+    PinName d2, PinName d3, int columns, int rows) : _rw(rw), _rs(rs), 
+    _e(e), _d(d0, d1, d2, d3), _columns(columns), _rows(rows) {
+
+//    _rows = 2;
+//    _columns = 16;
+    // Mon, 27 Apr 2009 23:32:34 +0200
+    // Kevin Konradt:
+    // When using a LCD with 1 row x 16 characters
+    // instead of 2x16, try changing _columns to 8.
+    // (display seems to split the 16 characters into 
+    // 2 virtual rows with 8 characters each.)
+
+    _rw = 0;
+    _e  = 1;
+    _rs = 0; // command mode
+
+    // Should theoretically wait 15ms, but most things will be powered up pre-reset
+    // so i'll disable that for the minute. If implemented, could wait 15ms post reset
+    // instead
+    // wait(0.015); 
+        
+    // send "Display Settings" 3 times (Only top nibble of 0x30 as we've got 4-bit bus)
+    for(int i=0; i<3; i++) {
+        writeNibble(0x3);
+        wait(0.00164);      // this command takes 1.64ms, so wait for it
+    }
+    writeNibble(0x2); // 4-bit mode
+            
+    writeCommand(0x28);    // Function set 001 BW N F - -  
+    writeCommand(0x0C);
+    writeCommand(0x6);  //  Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
+    
+    cls();
+}
+
+int TextLCD::_putc(int value) {
+    if(value == '\n') {
+        newline();
+    } else {
+        writeData(value);
+    }
+    return value;
+}
+
+int TextLCD::_getc() {
+    return 0;
+}
+
+void TextLCD::newline() {
+    _column = 0;
+    _row++;
+    if(_row >= _rows) {
+        _row = 0;
+    }
+    locate(_column, _row); 
+}
+
+void TextLCD::locate(int column, int row) {
+    if(column < 0 || column >= _columns || row < 0 || row >= _rows) {
+        error("locate(%d,%d) out of range on %dx%d display", column, row, _columns, _rows);
+        return;
+    }
+    
+    _row = row;
+      _column = column;
+      int address = 0x80 + (_row * 40) + _column; // memory starts at 0x80, and is 40 chars long per row
+      writeCommand(address);            
+}
+
+void TextLCD::cls() {
+    writeCommand(0x01); // Clear Display
+    wait(0.00164f);        // This command takes 1.64 ms
+      locate(0, 0);
+}
+
+void TextLCD::reset() {
+    cls();
+}
+
+void TextLCD::clock() {
+    wait(0.000040f);
+    _e = 0;
+    wait(0.000040f);  // most instructions take 40us
+    _e = 1;    
+}
+
+void TextLCD::writeNibble(int value) {
+    _d = value;
+    clock();
+}
+
+void TextLCD::writeByte(int value) {
+    writeNibble(value >> 4);
+    writeNibble(value >> 0);
+}
+
+void TextLCD::writeCommand(int command) {
+    _rs = 0;
+    writeByte(command);
+}
+
+void TextLCD::writeData(int data) {
+    _rs = 1;
+    writeByte(data);
+    _column++;
+    if(_column >= _columns) {
+        newline();
+    } 
+}
diff -r 000000000000 -r b77078f30b97 TextLCD.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TextLCD.h	Tue Nov 17 10:16:30 2009 +0000
@@ -0,0 +1,111 @@
+/* mbed TextLCD Library
+ * Copyright (c) 2007-2009 sford
+ * Released under the MIT License: http://mbed.org/license/mit
+ *
+ * TODO: Needs serious rework/neatening up!
+ */
+ 
+#ifndef MBED_TEXTLCD_H
+#define MBED_TEXTLCD_H
+
+#include "Stream.h"
+#include "DigitalOut.h"
+#include "BusOut.h"
+
+namespace mbed {
+
+/* Class: TextLCD
+ * A 16x2 Text LCD controller
+ *
+ * Allows you to print to a Text LCD screen, and locate/cls. Could be
+ * turned in to a more generic libray.
+ *
+ * If you are connecting multiple displays, you can connect them all in
+ * parallel except for the enable (e) pin, which must be unique for each
+ * display.
+ *
+ * Example:
+ * > #include "mbed.h"
+ * > #include "TextLCD.h"
+ * >
+ * > TextLCD lcd(p24, p25, p26, p27, p28, p29, p30); // rs, rw, e, d0, d1, d2, d3
+ * >
+ * > int main() {
+ * >     lcd.printf("Hello World!");
+ * > }
+ */
+class TextLCD : public Stream {
+
+public:
+    /* Constructor: TextLCD
+     * Create a TextLCD object, connected to the specified pins
+     *
+     * All signals must be connected to DigitalIn compatible pins. 
+     *
+     * Variables:
+     *  rs -  Used to specify data or command
+     *  rw - Used to determine read or write
+     *  e - enable
+     *  d0..d3 - The data lines
+     */
+    TextLCD(PinName rs, PinName rw, PinName e, PinName d0, PinName d1, 
+        PinName d2, PinName d3, int columns = 16, int rows = 2);
+
+#if 0 // Inhereted from Stream, for documentation only
+    /* Function: putc
+     *  Write a character
+     *
+     * Variables:
+     *  c - The character to write to the serial port
+     */
+    int putc(int c);
+
+    /* Function: printf
+     *  Write a formated string
+     *
+     * Variables:
+     *  format - A printf-style format string, followed by the
+     *      variables to use in formating the string.
+     */
+    int printf(const char* format, ...);
+#endif
+        
+    /* Function: locate
+     * Locate to a certian position
+     *
+     * Variables:
+     *  column - the column to locate to, from 0..15
+     *  row - the row to locate to, from 0..1
+     */
+    virtual void locate(int column, int row);
+    
+    /* Function: cls
+     * Clear the screen, and locate to 0,0
+     */
+    virtual void cls();    
+    
+    virtual void reset();
+        
+//protected:
+
+    void clock();
+    void writeData(int data);
+    void writeCommand(int command);
+    void writeByte(int value);
+    void writeNibble(int value);
+    virtual int _putc(int c);        
+    virtual int _getc();
+    virtual void newline();                
+            
+    int _row;
+    int _column;    
+    DigitalOut _rw, _rs, _e;
+    BusOut _d;
+    int _columns;
+    int _rows;
+
+};
+
+}
+
+#endif
diff -r 000000000000 -r b77078f30b97 main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Nov 17 10:16:30 2009 +0000
@@ -0,0 +1,37 @@
+// Write to all HD44780 TextLCD RAM locations, sford
+//
+// A quick hack to write to all the display RAM locations
+// in an HD44780 display, to identify which location maps
+// to which character.
+//
+// Instructions:
+//  - Change TextLCD pinout as appropriate so it works
+//  - Run, and it should fill the screen with characters
+//  - Identify what characters are at the start of each row
+//
+// To determine what address each line starts at, you subtract the 
+// ascii code for '0'(48) from the character at the start of each line
+//  - see http://www.asciitable.com/
+// 
+// e.g.
+//   +----------------+
+//   |0123456789:;<=>?| first char = '0' (48)
+//   |XYZ....         | first char = 'X' (88)
+//   +----------------+
+//  
+// So in this case, the RAM offsets are 0 and 40
+
+#include "mbed.h"
+#include "TextLCD.h"
+
+TextLCD lcd(p10, p11, p12, p15, p16, p29, p30);
+DigitalOut led(LED1);
+
+int main() {
+    lcd.locate(0,0);
+    for(int i=0; i<80; i++) {
+        lcd._rs = 1; 
+        lcd.writeByte('0' + i);
+    }
+}
+
diff -r 000000000000 -r b77078f30b97 mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Tue Nov 17 10:16:30 2009 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/d1a9de3f4fe0