cristian rodriguez
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TextLCD_20X4.cpp
00001 /* mbed TextLCD Library 00002 * Copyright (c) 2007-2009 sford 00003 * Released under the MIT License: http://mbed.org/license/mit 00004 * 00005 * TODO: Needs serious rework/neatening up! 00006 */ 00007 00008 /* 00009 * 2010/05/14 modified for 20X4 LCD by ym1784 00010 */ 00011 00012 #include "TextLCD_20X4.h" 00013 00014 #include "mbed.h" 00015 #include "error.h" 00016 00017 using namespace mbed; 00018 00019 /* 00020 * useful info found at http://www.a-netz.de/lcd.en.php 00021 * 00022 * 00023 * Initialization 00024 * ============== 00025 * 00026 * After attaching the supply voltage/after a reset, the display needs to be brought in to a defined state 00027 * 00028 * - wait approximately 15 ms so the display is ready to execute commands 00029 * - Execute the command 0x30 ("Display Settings") three times (wait 1,64ms after each command, the busy flag cannot be queried now). 00030 * - 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. 00031 * - If you want to use the 4 bit mode, now you can execute the command to switch over to this mode now. 00032 * - Execute the "clear display" command 00033 * 00034 * Timing 00035 * ====== 00036 * 00037 * Nearly all commands transmitted to the display need 40us for execution. 00038 * Exceptions are the commands "Clear Display and Reset" and "Set Cursor to Start Position" 00039 * These commands need 1.64ms for execution. These timings are valid for all displays working with an 00040 * internal clock of 250kHz. But I do not know any displays that use other frequencies. Any time you 00041 * can use the busy flag to test if the display is ready to accept the next command. 00042 * 00043 * _e is kept high apart from calling clock 00044 * _rw is kept 0 (write) apart from actions that uyse it differently 00045 * -> on this program, the _rw is not used ... ym1784 00046 * _rs is set by the data/command writes 00047 */ 00048 00049 TextLCD_20X4::TextLCD_20X4(PinName rs, PinName e, PinName d0, PinName d1, 00050 PinName d2, PinName d3, int columns, int rows) : _rs(rs), _e(e), _d(d0, d1, d2, d3), 00051 _columns(columns), _rows(rows) { 00052 00053 _rows = 4; 00054 _columns = 20; 00055 // Mon, 27 Apr 2009 23:32:34 +0200 00056 // Kevin Konradt: 00057 // When using a LCD with 1 row x 16 characters 00058 // instead of 2x16, try changing _columns to 8. 00059 // (display seems to split the 16 characters into 00060 // 2 virtual rows with 8 characters each.) 00061 // 00062 // 2010/05/14 ym1784 00063 // This program is only for 4 rows x 20 characters specific 00064 00065 // _rw = 0; // on this program, the _rw is not used ... ym1784 00066 _e = 1; 00067 _rs = 0; // command mode 00068 00069 // Should theoretically wait 15ms, but most things will be powered up pre-reset 00070 // so i'll disable that for the minute. If implemented, could wait 15ms post reset 00071 // instead 00072 wait(0.015); // for safety ... ym1784 00073 00074 // send "Display Settings" 3 times (Only top nibble of 0x30 as we've got 4-bit bus) 00075 for(int i=0; i<3; i++) { 00076 writeNibble(0x3); 00077 wait(0.00164); // this command takes 1.64ms, so wait for it 00078 } 00079 writeNibble(0x2); // 4-bit mode 00080 00081 writeCommand(0x28); // Function set 001 BW N F - - 00082 writeCommand(0x0C); 00083 writeCommand(0x6); // Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes 00084 00085 cls(); 00086 } 00087 00088 int TextLCD_20X4::_putc(int value) { 00089 if(value == '\n') { 00090 newline(); 00091 } else { 00092 writeData(value); 00093 } 00094 return value; 00095 } 00096 00097 int TextLCD_20X4::_getc() { 00098 return 0; 00099 } 00100 00101 void TextLCD_20X4::newline() { 00102 _column = 0; 00103 _row++; 00104 if(_row >= _rows) { 00105 _row = 0; 00106 } 00107 locate(_column, _row); 00108 } 00109 00110 void TextLCD_20X4::locate(int column, int row) { 00111 if(column < 0 || column >= _columns || row < 0 || row >= _rows) { 00112 error("locate(%d,%d) out of range on %dx%d display", column, row, _columns, _rows); 00113 return; 00114 } 00115 _row = row; 00116 _column = column; 00117 // modified for 20X4 LCD 00118 switch (_row) { 00119 case (0) : address = 0x80 + _column; 00120 break; 00121 case (1) : address = 0xc0 + _column; 00122 break; 00123 case (2) : address = 0x94 + _column; 00124 break; 00125 case (3) : address = 0xd4 + _column; 00126 break; 00127 } // switch 00128 writeCommand(address); 00129 } 00130 00131 void TextLCD_20X4::cls() { 00132 writeCommand(0x01); // Clear Display 00133 wait(0.00164f); // This command takes 1.64 ms 00134 // locate(0, 0); // We don't have to do this here 00135 } 00136 00137 void TextLCD_20X4::reset() { 00138 cls(); 00139 } 00140 00141 void TextLCD_20X4::clock() { 00142 wait(0.000040f); 00143 _e = 0; 00144 wait(0.000040f); // most instructions take 40us 00145 _e = 1; 00146 } 00147 00148 void TextLCD_20X4::writeNibble(int value) { 00149 _d = value; 00150 clock(); 00151 } 00152 00153 void TextLCD_20X4::writeByte(int value) { 00154 writeNibble(value >> 4); 00155 writeNibble(value >> 0); 00156 } 00157 00158 void TextLCD_20X4::writeCommand(int command) { 00159 _rs = 0; 00160 writeByte(command); 00161 } 00162 00163 void TextLCD_20X4::writeData(int data) { 00164 _rs = 1; 00165 writeByte(data); 00166 _column++; 00167 if(_column >= _columns) { 00168 newline(); 00169 } 00170 }
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