Revision 0:b77078f30b97, committed 2009-11-17

Comitter:

simon

Date:

Tue Nov 17 10:16:30 2009 +0000

Commit message:

Changed in this revision

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