Lee Kai Xuan / mbed-os

mbed-os

Fork of mbed-os by erkin yucel

features/unsupported/tests/mbed/freopen/TextLCD.cpp@0:f269e3021894, 2016-10-23 (annotated)

Committer:
elessair
Date:
Sun Oct 23 15:10:02 2016 +0000
Revision:
0:f269e3021894
Initial commit

Who changed what in which revision?

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elessair 0:f269e3021894 1 /* mbed TextLCD Library
elessair 0:f269e3021894 2 * Copyright (c) 2007-2009 sford
elessair 0:f269e3021894 3 * Released under the MIT License: http://mbed.org/license/mit
elessair 0:f269e3021894 4 */
elessair 0:f269e3021894 5
elessair 0:f269e3021894 6 #include "TextLCD.h"
elessair 0:f269e3021894 7 #include "mbed.h"
elessair 0:f269e3021894 8
elessair 0:f269e3021894 9 /*
elessair 0:f269e3021894 10 * useful info found at http://www.a-netz.de/lcd.en.php
elessair 0:f269e3021894 11 *
elessair 0:f269e3021894 12 * Initialisation
elessair 0:f269e3021894 13 * ==============
elessair 0:f269e3021894 14 *
elessair 0:f269e3021894 15 * After attaching the supply voltage/after a reset, the display needs to be brought in to a defined state
elessair 0:f269e3021894 16 *
elessair 0:f269e3021894 17 * - wait approximately 15 ms so the display is ready to execute commands
elessair 0:f269e3021894 18 * - Execute the command 0x30 ("Display Settings") three times (wait 1,64ms after each command, the busy flag cannot be queried now).
elessair 0:f269e3021894 19 * - 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.
elessair 0:f269e3021894 20 * - If you want to use the 4 bit mode, now you can execute the command to switch over to this mode now.
elessair 0:f269e3021894 21 * - Execute the "clear display" command
elessair 0:f269e3021894 22 *
elessair 0:f269e3021894 23 * Timing
elessair 0:f269e3021894 24 * ======
elessair 0:f269e3021894 25 *
elessair 0:f269e3021894 26 * Nearly all commands transmitted to the display need 40us for execution.
elessair 0:f269e3021894 27 * Exceptions are the commands "Clear Display and Reset" and "Set Cursor to Start Position"
elessair 0:f269e3021894 28 * These commands need 1.64ms for execution. These timings are valid for all displays working with an
elessair 0:f269e3021894 29 * internal clock of 250kHz. But I do not know any displays that use other frequencies. Any time you
elessair 0:f269e3021894 30 * can use the busy flag to test if the display is ready to accept the next command.
elessair 0:f269e3021894 31 *
elessair 0:f269e3021894 32 * _e is kept high apart from calling clock
elessair 0:f269e3021894 33 * _rw is kept 0 (write) apart from actions that uyse it differently
elessair 0:f269e3021894 34 * _rs is set by the data/command writes
elessair 0:f269e3021894 35 */
elessair 0:f269e3021894 36
elessair 0:f269e3021894 37 TextLCD::TextLCD(PinName rs, PinName rw, PinName e, PinName d0, PinName d1,
elessair 0:f269e3021894 38 PinName d2, PinName d3, const char *name) : TextDisplay(name), _rw(rw), _rs(rs),
elessair 0:f269e3021894 39 _e(e), _d(d0, d1, d2, d3) {
elessair 0:f269e3021894 40
elessair 0:f269e3021894 41 _rw = 0;
elessair 0:f269e3021894 42 _e = 1;
elessair 0:f269e3021894 43 _rs = 0; // command mode
elessair 0:f269e3021894 44
elessair 0:f269e3021894 45 // Should theoretically wait 15ms, but most things will be powered up pre-reset
elessair 0:f269e3021894 46 // so i'll disable that for the minute. If implemented, could wait 15ms post reset
elessair 0:f269e3021894 47 // instead
elessair 0:f269e3021894 48 // wait(0.015);
elessair 0:f269e3021894 49
elessair 0:f269e3021894 50 // send "Display Settings" 3 times (Only top nibble of 0x30 as we've got 4-bit bus)
elessair 0:f269e3021894 51 for(int i=0; i<3; i++) {
elessair 0:f269e3021894 52 writeByte(0x3);
elessair 0:f269e3021894 53 wait(0.00164); // this command takes 1.64ms, so wait for it
elessair 0:f269e3021894 54 }
elessair 0:f269e3021894 55 writeByte(0x2); // 4-bit mode
elessair 0:f269e3021894 56
elessair 0:f269e3021894 57 writeCommand(0x28); // Function set 001 BW N F - -
elessair 0:f269e3021894 58 writeCommand(0x0C);
elessair 0:f269e3021894 59 writeCommand(0x6); // Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
elessair 0:f269e3021894 60 cls();
elessair 0:f269e3021894 61 }
elessair 0:f269e3021894 62
elessair 0:f269e3021894 63 void TextLCD::character(int column, int row, int c) {
elessair 0:f269e3021894 64 int address = 0x80 + (row * 40) + column; // memory starts at 0x80, and is 40 chars long per row
elessair 0:f269e3021894 65 writeCommand(address);
elessair 0:f269e3021894 66 writeData(c);
elessair 0:f269e3021894 67 }
elessair 0:f269e3021894 68
elessair 0:f269e3021894 69 int TextLCD::columns() {
elessair 0:f269e3021894 70 return 16;
elessair 0:f269e3021894 71 }
elessair 0:f269e3021894 72
elessair 0:f269e3021894 73 int TextLCD::rows() {
elessair 0:f269e3021894 74 return 2;
elessair 0:f269e3021894 75 }
elessair 0:f269e3021894 76
elessair 0:f269e3021894 77 void TextLCD::writeByte(int value) {
elessair 0:f269e3021894 78 _d = value >> 4;
elessair 0:f269e3021894 79 wait(0.000040f); // most instructions take 40us
elessair 0:f269e3021894 80 _e = 0;
elessair 0:f269e3021894 81 wait(0.000040f);
elessair 0:f269e3021894 82 _e = 1;
elessair 0:f269e3021894 83 _d = value >> 0;
elessair 0:f269e3021894 84 wait(0.000040f);
elessair 0:f269e3021894 85 _e = 0;
elessair 0:f269e3021894 86 wait(0.000040f); // most instructions take 40us
elessair 0:f269e3021894 87 _e = 1;
elessair 0:f269e3021894 88 }
elessair 0:f269e3021894 89
elessair 0:f269e3021894 90 void TextLCD::writeCommand(int command) {
elessair 0:f269e3021894 91 _rs = 0;
elessair 0:f269e3021894 92 writeByte(command);
elessair 0:f269e3021894 93 }
elessair 0:f269e3021894 94
elessair 0:f269e3021894 95 void TextLCD::writeData(int data) {
elessair 0:f269e3021894 96 _rs = 1;
elessair 0:f269e3021894 97 writeByte(data);
elessair 0:f269e3021894 98 }