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| simon |
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/* mbed TextLCD Library
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* Copyright (c) 2007-2009 sford
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* Released under the MIT License: http://mbed.org/license/mit
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*/
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#include "TextLCD.h"
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#include "mbed.h"
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/*
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* useful info found at http://www.a-netz.de/lcd.en.php
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*
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* Initialisation
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* ==============
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*
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* After attaching the supply voltage/after a reset, the display needs to be brought in to a defined state
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*
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* - wait approximately 15 ms so the display is ready to execute commands
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* - Execute the command 0x30 ("Display Settings") three times (wait 1,64ms after each command, the busy flag cannot be queried now).
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* - 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.
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* - If you want to use the 4 bit mode, now you can execute the command to switch over to this mode now.
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* - Execute the "clear display" command
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*
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* Timing
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* ======
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*
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* Nearly all commands transmitted to the display need 40us for execution.
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* Exceptions are the commands "Clear Display and Reset" and "Set Cursor to Start Position"
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* These commands need 1.64ms for execution. These timings are valid for all displays working with an
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* internal clock of 250kHz. But I do not know any displays that use other frequencies. Any time you
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* can use the busy flag to test if the display is ready to accept the next command.
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*
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* _e is kept high apart from calling clock
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* _rw is kept 0 (write) apart from actions that uyse it differently
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* _rs is set by the data/command writes
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*/
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TextLCD::TextLCD(PinName rs, PinName rw, PinName e, PinName d0, PinName d1,
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PinName d2, PinName d3, const char *name) : TextDisplay(name), _rw(rw), _rs(rs),
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_e(e), _d(d0, d1, d2, d3) {
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_rw = 0;
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_e = 1;
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_rs = 0; // command mode
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// Should theoretically wait 15ms, but most things will be powered up pre-reset
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// so i'll disable that for the minute. If implemented, could wait 15ms post reset
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// instead
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// wait(0.015);
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// send "Display Settings" 3 times (Only top nibble of 0x30 as we've got 4-bit bus)
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for(int i=0; i<3; i++) {
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writeByte(0x3);
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wait(0.00164); // this command takes 1.64ms, so wait for it
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}
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writeByte(0x2); // 4-bit mode
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writeCommand(0x28); // Function set 001 BW N F - -
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writeCommand(0x0C);
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writeCommand(0x6); // Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
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cls();
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}
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void TextLCD::character(int column, int row, int c) {
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int address = 0x80 + (row * 40) + column; // memory starts at 0x80, and is 40 chars long per row
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writeCommand(address);
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writeData(c);
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}
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int TextLCD::columns() {
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return 16;
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}
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int TextLCD::rows() {
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return 2;
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}
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void TextLCD::writeByte(int value) {
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_d = value >> 4;
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wait(0.000040f); // most instructions take 40us
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_e = 0;
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wait(0.000040f);
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_e = 1;
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_d = value >> 0;
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wait(0.000040f);
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_e = 0;
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wait(0.000040f); // most instructions take 40us
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_e = 1;
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}
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void TextLCD::writeCommand(int command) {
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_rs = 0;
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writeByte(command);
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}
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void TextLCD::writeData(int data) {
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_rs = 1;
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writeByte(data);
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}
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Simon Ford