Diff: TextLCD_20X4.cpp

Revision:

0:6089ae824f06

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TextLCD_20X4.cpp	Mon Dec 26 15:58:32 2011 +0000
@@ -0,0 +1,170 @@
+/* mbed TextLCD Library
+ * Copyright (c) 2007-2009 sford
+ * Released under the MIT License: http://mbed.org/license/mit
+ *
+ * TODO: Needs serious rework/neatening up!
+ */
+
+/*
+ *  2010/05/14 modified for 20X4 LCD by ym1784
+ */
+
+#include "TextLCD_20X4.h"
+
+#include "mbed.h"
+#include "error.h"
+
+using namespace mbed;
+
+/*
+ * useful info found at http://www.a-netz.de/lcd.en.php
+ *
+ *
+ * Initialization
+ * ==============
+ *
+ * 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
+ *  -> on this program, the _rw is not used ... ym1784
+ * _rs is set by the data/command writes
+ */
+
+TextLCD_20X4::TextLCD_20X4(PinName rs, PinName e, PinName d0, PinName d1,
+    PinName d2, PinName d3, int columns, int rows) : _rs(rs), _e(e), _d(d0, d1, d2, d3),
+    _columns(columns), _rows(rows) {
+
+    _rows = 4;
+    _columns = 20;
+    // 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.)
+    //
+    // 2010/05/14 ym1784
+    // This program is only for 4 rows x 20 characters specific
+
+//  _rw = 0; // on this program, the _rw is not used ... ym1784
+    _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); // for safety ... ym1784
+        
+    // 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_20X4::_putc(int value) {
+    if(value == '\n') {
+        newline();
+    } else {
+        writeData(value);
+    }
+    return value;
+}
+
+int TextLCD_20X4::_getc() {
+    return 0;
+}
+
+void TextLCD_20X4::newline() {
+    _column = 0;
+    _row++;
+    if(_row >= _rows) {
+        _row = 0;
+    }
+    locate(_column, _row);
+}
+
+void TextLCD_20X4::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;
+// modified for 20X4 LCD
+    switch (_row) {
+        case (0) : address = 0x80 + _column;
+        break;
+        case (1) : address = 0xc0 + _column;
+        break;
+        case (2) : address = 0x94 + _column;
+        break;
+        case (3) : address = 0xd4 + _column;
+        break;
+        } // switch
+    writeCommand(address);
+}
+
+void TextLCD_20X4::cls() {
+    writeCommand(0x01); // Clear Display
+    wait(0.00164f);     // This command takes 1.64 ms
+//    locate(0, 0);     // We don't have to do this here
+}
+
+void TextLCD_20X4::reset() {
+    cls();
+}
+
+void TextLCD_20X4::clock() {
+    wait(0.000040f);
+    _e = 0;
+    wait(0.000040f);  // most instructions take 40us
+    _e = 1;
+}
+
+void TextLCD_20X4::writeNibble(int value) {
+    _d = value;
+    clock();
+}
+
+void TextLCD_20X4::writeByte(int value) {
+    writeNibble(value >> 4);
+    writeNibble(value >> 0);
+}
+
+void TextLCD_20X4::writeCommand(int command) {
+    _rs = 0;
+    writeByte(command);
+}
+
+void TextLCD_20X4::writeData(int data) {
+    _rs = 1;
+    writeByte(data);
+    _column++;
+    if(_column >= _columns) {
+        newline();
+    }
+}