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/* mbed I2CTextLCD Library
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* Copyright (c) 2007-2009 sford
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* Copyright (c) 2010 Wim De Roeve changed to work with I2C PCF8575
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* Released under the MIT License: http://mbed.org/license/mit
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*/
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#include "I2CTextLCD.h"
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#include "mbed.h"
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#include "error.h"
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using namespace mbed;
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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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*
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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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*/
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I2CTextLCD::I2CTextLCD(PinName sda, PinName scl, int i2cAddress , int columns, int rows) :
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_i2c(sda, scl) {
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_i2cAddress = i2cAddress;
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_columns = columns;
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_rows = rows;
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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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writeNibble(0x3,false);
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wait(0.00164); // this command takes 1.64ms, so wait for it
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}
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writeNibble(0x2,false); // 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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int I2CTextLCD::_putc(int value) {
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if (value == '\n') {
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newline();
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} else {
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writeData(value);
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}
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return value;
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}
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int I2CTextLCD::_getc() {
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return 0;
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}
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void I2CTextLCD::newline() {
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_column = 0;
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_row++;
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if (_row >= _rows) {
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_row = 0;
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}
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locate(_column, _row);
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}
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void I2CTextLCD::locate(int column, int row) {
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if (column < 0 || column >= _columns || row < 0 || row >= _rows) {
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error("locate(%d,%d) out of range on %dx%d display", column, row, _columns, _rows);
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return;
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}
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_row = row;
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_column = column;
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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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// pc_LCD.traceOut("locate %dx%d\r\n", column, row);
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writeCommand(address);
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}
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void I2CTextLCD::cls() {
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writeCommand(0x01); // Clear Display
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wait(0.00164f); // This command takes 1.64 ms
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locate(0, 0);
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}
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void I2CTextLCD::reset() {
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cls();
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}
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void I2CTextLCD::writeNibble(int data, bool rs) {
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data = (data & 0xF);
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if (rs) {
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data = data | RS_ON; // set rs bit
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}
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writeI2CByte(data | E_ON); // E=1
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wait(0.000040f);
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writeI2CByte(data ); // E=0
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wait(0.000040f);
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writeI2CByte(data | E_ON); // E=1
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}
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void I2CTextLCD::writeByte(int data, bool rs) {
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writeNibble(data >> 4 , rs);
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writeNibble(data >> 0 , rs);
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}
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void I2CTextLCD::writeCommand(int command) {
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//command ^= RS_ON; // RS = 0;
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writeByte(command,false);
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}
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void I2CTextLCD::writeData(int data) {
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// data = data | RS_ON; //RS = 1
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writeByte(data,true);
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_column++;
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if (_column >= _columns) {
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newline();
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}
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}
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void I2CTextLCD::writeI2CByte(int data) {
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char cmd[2];
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cmd[0] = (data & 0xFF);
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cmd[1] = (data >> 8);
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_i2c.write(_i2cAddress, cmd, 2);
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}
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Wim De Roeve