I2CTextLCD - Driver for a Text LCD using a PCF8574 over I2C

Users » romilly » Code » I2CTextLCD

Romilly Cocking / Mbed 2 deprecated I2CTextLCD

Driver for a Text LCD using a PCF8574 over I2C

TextLCD.cpp@0:6beb6f498640, 2010-08-09 (annotated)

Committer:: romilly
Date:: Mon Aug 09 14:17:02 2010 +0000
Revision:: 0:6beb6f498640

Who changed what in which revision?

User	Revision	Line number	New contents of line
romilly	0:6beb6f498640	1	/* mbed I2CTextLCD Library, for a 4-bit LCD driven by I2C and a PCF8574
romilly	0:6beb6f498640	2	* Copyright (c) 2007-2010, sford, rcocking
romilly	0:6beb6f498640	3	*
romilly	0:6beb6f498640	4	* Permission is hereby granted, free of charge, to any person obtaining a copy
romilly	0:6beb6f498640	5	* of this software and associated documentation files (the "Software"), to deal
romilly	0:6beb6f498640	6	* in the Software without restriction, including without limitation the rights
romilly	0:6beb6f498640	7	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
romilly	0:6beb6f498640	8	* copies of the Software, and to permit persons to whom the Software is
romilly	0:6beb6f498640	9	* furnished to do so, subject to the following conditions:
romilly	0:6beb6f498640	10	*
romilly	0:6beb6f498640	11	* The above copyright notice and this permission notice shall be included in
romilly	0:6beb6f498640	12	* all copies or substantial portions of the Software.
romilly	0:6beb6f498640	13	*
romilly	0:6beb6f498640	14	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
romilly	0:6beb6f498640	15	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
romilly	0:6beb6f498640	16	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
romilly	0:6beb6f498640	17	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
romilly	0:6beb6f498640	18	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
romilly	0:6beb6f498640	19	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
romilly	0:6beb6f498640	20	* THE SOFTWARE.
romilly	0:6beb6f498640	21	*/
romilly	0:6beb6f498640	22
romilly	0:6beb6f498640	23	/* This is a hack of Simon Ford's direct-driven TextLCD code.
romilly	0:6beb6f498640	24	* It should be refactored to extract a common superclass
romilly	0:6beb6f498640	25	* but my C++ isn't yet good enough :)
romilly	0:6beb6f498640	26	*
romilly	0:6beb6f498640	27	* The code assumes the following connections between the PCF8574
romilly	0:6beb6f498640	28	* and the LCD
romilly	0:6beb6f498640	29	*
romilly	0:6beb6f498640	30	* nc - D0
romilly	0:6beb6f498640	31	* nc - D1
romilly	0:6beb6f498640	32	* nc - D2
romilly	0:6beb6f498640	33	* nc - D3
romilly	0:6beb6f498640	34	* P0 - D4
romilly	0:6beb6f498640	35	* P1 - D5
romilly	0:6beb6f498640	36	* P2 - D6
romilly	0:6beb6f498640	37	* P3 - D7
romilly	0:6beb6f498640	38	* P4 - E
romilly	0:6beb6f498640	39	* P5 - nc
romilly	0:6beb6f498640	40	* P6 - nc
romilly	0:6beb6f498640	41	* P7 - RS
romilly	0:6beb6f498640	42	* gnd - R/W
romilly	0:6beb6f498640	43	*
romilly	0:6beb6f498640	44	* D0-3 of the LCD are not connected because we work in 4-bit mode
romilly	0:6beb6f498640	45	* R/W is hardwired to gound, as we only ever write to the LCD
romilly	0:6beb6f498640	46	* A0-2 on the PCF8574 can be set in any combination; you will need to modify
romilly	0:6beb6f498640	47	* the I2C address in the I2CTextLCD constructor.
romilly	0:6beb6f498640	48	* Remember that the mbed uses 8-bit addresses, which should be
romilly	0:6beb6f498640	49	* in the range 0x40-0x4E for the PCF8574
romilly	0:6beb6f498640	50	*/
romilly	0:6beb6f498640	51	#include "TextLCD.h"
romilly	0:6beb6f498640	52	#include "mbed.h"
romilly	0:6beb6f498640	53
romilly	0:6beb6f498640	54	TextLCD::TextLCD(PinName sda, PinName scl, int i2cAddress, LCDType type) : _i2c(sda, scl),
romilly	0:6beb6f498640	55	_type(type) {
romilly	0:6beb6f498640	56	_i2cAddress = i2cAddress;
romilly	0:6beb6f498640	57	wait(0.015); // Wait 15ms to ensure powered up
romilly	0:6beb6f498640	58
romilly	0:6beb6f498640	59	// send "Display Settings" 3 times (Only top nibble of 0x30 as we've got 4-bit bus)
romilly	0:6beb6f498640	60	for (int i=0; i<3; i++) {
romilly	0:6beb6f498640	61	writeByte(0x3, false);
romilly	0:6beb6f498640	62	wait(0.00164); // this command takes 1.64ms, so wait for it
romilly	0:6beb6f498640	63	}
romilly	0:6beb6f498640	64	writeByte(0x2, false); // 4-bit mode
romilly	0:6beb6f498640	65	wait(0.000040f); // most instructions take 40us
romilly	0:6beb6f498640	66
romilly	0:6beb6f498640	67	writeCommand(0x28); // Function set 001 BW N F - -
romilly	0:6beb6f498640	68	writeCommand(0x0C);
romilly	0:6beb6f498640	69	writeCommand(0x6); // Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
romilly	0:6beb6f498640	70	cls();
romilly	0:6beb6f498640	71	}
romilly	0:6beb6f498640	72
romilly	0:6beb6f498640	73	void TextLCD::character(int column, int row, int c) {
romilly	0:6beb6f498640	74	int a = address(column, row);
romilly	0:6beb6f498640	75	writeCommand(a);
romilly	0:6beb6f498640	76	writeData(c);
romilly	0:6beb6f498640	77	}
romilly	0:6beb6f498640	78
romilly	0:6beb6f498640	79	void TextLCD::cls() {
romilly	0:6beb6f498640	80	writeCommand(0x01); // cls, and set cursor to 0
romilly	0:6beb6f498640	81	wait(0.00164f); // This command takes 1.64 ms
romilly	0:6beb6f498640	82	locate(0, 0);
romilly	0:6beb6f498640	83	}
romilly	0:6beb6f498640	84
romilly	0:6beb6f498640	85	void TextLCD::locate(int column, int row) {
romilly	0:6beb6f498640	86	_column = column;
romilly	0:6beb6f498640	87	_row = row;
romilly	0:6beb6f498640	88	}
romilly	0:6beb6f498640	89
romilly	0:6beb6f498640	90	int TextLCD::_putc(int value) {
romilly	0:6beb6f498640	91	if (value == '\n') {
romilly	0:6beb6f498640	92	_column = 0;
romilly	0:6beb6f498640	93	_row++;
romilly	0:6beb6f498640	94	if (_row >= rows()) {
romilly	0:6beb6f498640	95	_row = 0;
romilly	0:6beb6f498640	96	}
romilly	0:6beb6f498640	97	} else {
romilly	0:6beb6f498640	98	character(_column, _row, value);
romilly	0:6beb6f498640	99	_column++;
romilly	0:6beb6f498640	100	if (_column >= columns()) {
romilly	0:6beb6f498640	101	_column = 0;
romilly	0:6beb6f498640	102	_row++;
romilly	0:6beb6f498640	103	if (_row >= rows()) {
romilly	0:6beb6f498640	104	_row = 0;
romilly	0:6beb6f498640	105	}
romilly	0:6beb6f498640	106	}
romilly	0:6beb6f498640	107	}
romilly	0:6beb6f498640	108	return value;
romilly	0:6beb6f498640	109	}
romilly	0:6beb6f498640	110
romilly	0:6beb6f498640	111	int TextLCD::_getc() {
romilly	0:6beb6f498640	112	return -1;
romilly	0:6beb6f498640	113	}
romilly	0:6beb6f498640	114
romilly	0:6beb6f498640	115	void TextLCD::writeI2CByte(int data) {
romilly	0:6beb6f498640	116	// equivalent to writeI2CByte
romilly	0:6beb6f498640	117	char * cmd = new char[1];
romilly	0:6beb6f498640	118	cmd[0] = data;
romilly	0:6beb6f498640	119	_i2c.write(_i2cAddress, cmd, 1);
romilly	0:6beb6f498640	120	}
romilly	0:6beb6f498640	121
romilly	0:6beb6f498640	122	void TextLCD::writeNibble(int data, bool rs) {
romilly	0:6beb6f498640	123	if (rs) {
romilly	0:6beb6f498640	124	data = data \| RS_ON; // set rs bit
romilly	0:6beb6f498640	125	}
romilly	0:6beb6f498640	126	data \|= E_ON; // E on
romilly	0:6beb6f498640	127	writeI2CByte(data);
romilly	0:6beb6f498640	128	data ^= E_ON; // E off
romilly	0:6beb6f498640	129	wait_us(1);
romilly	0:6beb6f498640	130	writeI2CByte(data);
romilly	0:6beb6f498640	131	wait_us(1000);
romilly	0:6beb6f498640	132	}
romilly	0:6beb6f498640	133
romilly	0:6beb6f498640	134	void TextLCD::writeByte(int data, bool rs) {
romilly	0:6beb6f498640	135	writeNibble(data >> 4, rs);
romilly	0:6beb6f498640	136	writeNibble(data & 0x0F, rs);
romilly	0:6beb6f498640	137	}
romilly	0:6beb6f498640	138
romilly	0:6beb6f498640	139	void TextLCD::writeCommand(int command) {
romilly	0:6beb6f498640	140	// equivalent to ard commandWrite
romilly	0:6beb6f498640	141	writeByte(command, false);
romilly	0:6beb6f498640	142	}
romilly	0:6beb6f498640	143
romilly	0:6beb6f498640	144	void TextLCD::writeData(int data) {
romilly	0:6beb6f498640	145
romilly	0:6beb6f498640	146	writeByte(data, true);
romilly	0:6beb6f498640	147	}
romilly	0:6beb6f498640	148
romilly	0:6beb6f498640	149	int TextLCD::address(int column, int row) {
romilly	0:6beb6f498640	150	switch (_type) {
romilly	0:6beb6f498640	151	case LCD20x4:
romilly	0:6beb6f498640	152	switch (row) {
romilly	0:6beb6f498640	153	case 0:
romilly	0:6beb6f498640	154	return 0x80 + column;
romilly	0:6beb6f498640	155	case 1:
romilly	0:6beb6f498640	156	return 0xc0 + column;
romilly	0:6beb6f498640	157	case 2:
romilly	0:6beb6f498640	158	return 0x94 + column;
romilly	0:6beb6f498640	159	case 3:
romilly	0:6beb6f498640	160	return 0xd4 + column;
romilly	0:6beb6f498640	161	}
romilly	0:6beb6f498640	162	case LCD16x2B:
romilly	0:6beb6f498640	163	return 0x80 + (row * 40) + column;
romilly	0:6beb6f498640	164	case LCD16x2:
romilly	0:6beb6f498640	165	case LCD20x2:
romilly	0:6beb6f498640	166	default:
romilly	0:6beb6f498640	167	return 0x80 + (row * 0x40) + column;
romilly	0:6beb6f498640	168	}
romilly	0:6beb6f498640	169	}
romilly	0:6beb6f498640	170
romilly	0:6beb6f498640	171	int TextLCD::columns() {
romilly	0:6beb6f498640	172	switch (_type) {
romilly	0:6beb6f498640	173	case LCD20x4:
romilly	0:6beb6f498640	174	case LCD20x2:
romilly	0:6beb6f498640	175	return 20;
romilly	0:6beb6f498640	176	case LCD16x2:
romilly	0:6beb6f498640	177	case LCD16x2B:
romilly	0:6beb6f498640	178	default:
romilly	0:6beb6f498640	179	return 16;
romilly	0:6beb6f498640	180	}
romilly	0:6beb6f498640	181	}
romilly	0:6beb6f498640	182
romilly	0:6beb6f498640	183	int TextLCD::rows() {
romilly	0:6beb6f498640	184	switch (_type) {
romilly	0:6beb6f498640	185	case LCD20x4:
romilly	0:6beb6f498640	186	return 4;
romilly	0:6beb6f498640	187	case LCD16x2:
romilly	0:6beb6f498640	188	case LCD16x2B:
romilly	0:6beb6f498640	189	case LCD20x2:
romilly	0:6beb6f498640	190	default:
romilly	0:6beb6f498640	191	return 2;
romilly	0:6beb6f498640	192	}
romilly	0:6beb6f498640	193	}

Repository toolbox

Export to desktop IDE

Build repository

Repository details

Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	09 Aug 2010
Imports:	1820
Forks:	2
Commits:	1
Dependents:	0
Dependencies:	1
Followers:	28

TextLCD.cpp@0:6beb6f498640, 2010-08-09 (annotated)

Who changed what in which revision?

Repository toolbox

Repository details

Important Information for this Arm website

Access Warning