TextLCD for threaded applications
Diff: TextLCD.cpp
- Revision:
- 0:edfb85c53631
- Child:
- 1:ac48b187213c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/TextLCD.cpp Sat May 22 18:18:19 2010 +0000 @@ -0,0 +1,115 @@ +/* mbed TextLCD Library, 4-bit 2x16 + * Copyright (c) 2007-2010, sford + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include "TextLCD.h" +#include "mbed.h" + +/* + * 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) : _rw(rw), _rs(rs), + _e(e), _d(d0, d1, d2, d3) { + + _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++) { + writeByte(0x3); + wait(0.00164); // this command takes 1.64ms, so wait for it + } + writeByte(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(); +} + +void TextLCD::character(int column, int row, int c) { + int address = 0x80 + (row * 40) + column; // memory starts at 0x80, and is 40 chars long per row + writeCommand(address); + writeData(c); +} + +int TextLCD::columns() { + return 16; +} + +int TextLCD::rows() { + return 2; +} + +void TextLCD::writeByte(int value) { + _d = value >> 4; + wait(0.000040f); // most instructions take 40us + _e = 0; + wait(0.000040f); + _e = 1; + _d = value >> 0; + wait(0.000040f); + _e = 0; + wait(0.000040f); // most instructions take 40us + _e = 1; +} + +void TextLCD::writeCommand(int command) { + _rs = 0; + writeByte(command); +} + +void TextLCD::writeData(int data) { + _rs = 1; + writeByte(data); +}