TextLCD.cpp

00001 /* mbed TextLCD Library
00002  * Copyright (c) 2007-2009 sford
00003  * Released under the MIT License: http://mbed.org/license/mit
00004  *
00005  * Modified by Ned Konz to provide better support for 4-line LCDs and ones with other controller chips.
00006  */
00007 
00008 #include "TextLCD.h"
00009 #include "mbed.h"
00010 
00011 /*
00012  * useful info found at http://www.a-netz.de/lcd.en.php
00013  *
00014  * Initialisation
00015  * ==============
00016  *
00017  * After attaching the supply voltage/after a reset, the display needs to be brought in to a defined state
00018  *
00019  * - wait approximately 15 ms so the display is ready to execute commands
00020  * - Execute the command 0x30 ("Display Settings") three times (wait 1,64ms after each command, the busy flag cannot be queried now).
00021  * - 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.
00022  * - If you want to use the 4 bit mode, now you can execute the command to switch over to this mode now.
00023  * - Execute the "clear display" command
00024  *
00025  * Timing
00026  * ======
00027  *
00028  * Nearly all commands transmitted to the display need 40us for execution.
00029  * Exceptions are the commands "Clear Display and Reset" and "Set Cursor to Start Position"
00030  * These commands need 1.64ms for execution. These timings are valid for all displays working with an
00031  * internal clock of 250kHz. But I do not know any displays that use other frequencies. Any time you
00032  * can use the busy flag to test if the display is ready to accept the next command.
00033  *
00034  * _e is kept low except when being used.
00035  * _rw is kept 0 (write) apart from actions that use it differently
00036  * _rs is set by the data/command writes
00037  */
00038 
00039 TextLCD::TextLCD(PinName rs, PinName rw, PinName e, PinName d0, PinName d1,
00040                  PinName d2, PinName d3, uint16_t rows, uint16_t cols) : _rw(rw), _rs(rs),
00041         _e(e), _d(d0, d1, d2, d3), _rows(rows), _columns(cols) {
00042 
00043     _rw = 0;
00044     wait_us(1);     // min. 100nsec delay
00045     _e  = 0;
00046     _rs = 0;    // command mode
00047     _d.output();
00048 
00049     reset();
00050     cls();
00051 }
00052 
00053 void TextLCD::reset() {
00054     wait_ms(15);
00055     // e is low at this point, as is rw.
00056     // 2. Send 0x3 and wait 150 ms (will stay in 8-bit mode if already there)
00057     writeHalfByte(0x3);
00058     wait_ms(5);
00059     // 3. Send 0x3 and wait 150 ms (will go to 8-bit mode if was in 4-bit without any garbage nibble)
00060     writeHalfByte(0x3);
00061     wait_ms(5);
00062     // 4. Send 0x3 and wait 250 ms (will go to 8-bit mode even if garbage nibble was previously received)
00063     writeHalfByte(0x3);
00064     wait_ms(5);
00065     // 5. Send 0x2 and wait 200 ms (should go to 4-bit mode now)
00066     writeHalfByte(0x2);
00067     wait_ms(5);
00068     // 7. Send LCD setup sequence (eg 0x2, 0x8 (=0x28), 0x0, 0x8 (=0x08), etc.)
00069     writeCommand(0x28);    // Function set 001 BW N F - -
00070     wait_ms(15);
00071 
00072     writeCommand(0x08);     // display off, cursor invisible
00073     wait_ms(15);
00074 
00075     writeCommand(0x01);
00076     wait_ms(15);      // 1.64ms command
00077 
00078     writeCommand(0x0C);     // display enabled, cursor invisible
00079     wait_ms(15);
00080 
00081     writeCommand(0x6);  //  Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
00082     wait_ms(15);
00083 
00084     locate(0,0);
00085 }
00086 
00087 // memory starts at 0x80, and is 0x40 chars long per row
00088 // However, rows 2 and 3 of 4-line displays are actually adjacent to rows 0 and 1.
00089 // 16x4 displays are addressed the same way as 20x4 ones.
00090 
00091 void TextLCD::character(uint16_t column, uint16_t row, int c) {
00092     int address;
00093     address = 0x80 + ((row & ~2) * 0x40) + column;
00094     if (row > 1)
00095         address += 20;
00096     writeCommand(address);
00097     writeData(c);
00098 }
00099 
00100 void TextLCD::writeHalfByte(uint16_t value) {
00101     _e = 1;
00102     wait_us(1);
00103     _d = value & 0x0F;    // send data on bus
00104     wait_us(1); // setup time
00105     _e = 0; // strobe
00106     wait_us(1); // hold time
00107 }
00108 
00109 void TextLCD::writeByte(uint16_t value) {
00110     writeHalfByte(value>>4);
00111     writeHalfByte(value);
00112 }
00113 
00114 void TextLCD::writeCommand(uint16_t command) {
00115     _rs = 0;
00116     writeByte(command);
00117     waitUntilDone();
00118 }
00119 
00120 void TextLCD::writeData(uint16_t data) {
00121     _rs = 1;
00122     writeByte(data);
00123     waitUntilDone();
00124 }
00125 
00126 void TextLCD::cls() {
00127     writeCommand(0x01);
00128     wait_us(2000);      // 1.64ms command
00129     locate(0,0);
00130 }
00131 
00132 // This should be changed to use readAddressAndBusy() when that works.
00133 void TextLCD::waitUntilDone() {
00134     wait_us(60);
00135 }
00136 
00137 // Return the busy/address byte.
00138 // The busy flag is the high bit.
00139 // Not yet working reliably.
00140 uint16_t TextLCD::readAddressAndBusy() {
00141     _d.input();
00142     _rw = 1;
00143     wait_us(1);
00144     _e = 1;
00145     wait_us(1);
00146     _e = 0;
00147 
00148     uint16_t retval = _d.read() << 4;
00149 
00150     wait_us(1);
00151     _e = 1;
00152     wait_us(1);
00153     _e = 0;
00154 
00155     retval |= _d.read();
00156     _rw = 0;
00157 
00158     _d.output();
00159     return retval;
00160 }
00161