TextLCD.cpp

00001 /* mbed I2CTextLCD Library, for a 4-bit LCD driven by I2C and a PCF8574
00002  * Copyright (c) 2007-2010, sford, rcocking
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy
00005  * of this software and associated documentation files (the "Software"), to deal
00006  * in the Software without restriction, including without limitation the rights
00007  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008  * copies of the Software, and to permit persons to whom the Software is
00009  * furnished to do so, subject to the following conditions:
00010  *
00011  * The above copyright notice and this permission notice shall be included in
00012  * all copies or substantial portions of the Software.
00013  *
00014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00019  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
00020  * THE SOFTWARE.
00021  */
00022 
00023 /* This is a hack of Simon Ford's direct-driven TextLCD code.
00024 * It should be refactored to extract a common superclass
00025 * but my C++ isn't yet good enough :) 
00026 *
00027 * The code assumes the following connections between the PCF8574
00028 * and the LCD
00029 * 
00030 * nc  - D0
00031 * nc  - D1
00032 * nc  - D2
00033 * nc  - D3
00034 * P0  - D4
00035 * P1  - D5
00036 * P2  - D6
00037 * P3  - D7
00038 * P4  - E
00039 * P5  - nc
00040 * P6  - nc
00041 * P7  - RS
00042 * gnd - R/W
00043 *
00044 * D0-3 of the LCD are not connected because we work in 4-bit mode
00045 * R/W is hardwired to gound, as we only ever write to the LCD
00046 * A0-2 on the PCF8574 can be set in any combination; you will need to modify
00047 * the I2C address in the I2CTextLCD constructor.
00048 * Remember that the mbed uses 8-bit addresses, which should be
00049 * in the range 0x40-0x4E for the PCF8574
00050 */
00051 #include "TextLCD.h"
00052 #include "mbed.h"
00053 
00054 TextLCD::TextLCD(PinName sda, PinName scl, int i2cAddress, LCDType type) : _i2c(sda, scl),
00055         _type(type) {
00056     _i2cAddress = i2cAddress;
00057     wait(0.015);        // Wait 15ms to ensure powered up
00058 
00059     // send "Display Settings" 3 times (Only top nibble of 0x30 as we've got 4-bit bus)
00060     for (int i=0; i<3; i++) {
00061         writeByte(0x3, false);
00062         wait(0.00164);  // this command takes 1.64ms, so wait for it
00063     }
00064     writeByte(0x2, false);     // 4-bit mode
00065     wait(0.000040f);    // most instructions take 40us
00066 
00067     writeCommand(0x28); // Function set 001 BW N F - -
00068     writeCommand(0x0C);
00069     writeCommand(0x6);  // Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
00070     cls();
00071 }
00072 
00073 void TextLCD::character(int column, int row, int c) {
00074     int a = address(column, row);
00075     writeCommand(a);
00076     writeData(c);
00077 }
00078 
00079 void TextLCD::cls() {
00080     writeCommand(0x01); // cls, and set cursor to 0
00081     wait(0.00164f);     // This command takes 1.64 ms
00082     locate(0, 0);
00083 }
00084 
00085 void TextLCD::locate(int column, int row) {
00086     _column = column;
00087     _row = row;
00088 }
00089 
00090 int TextLCD::_putc(int value) {
00091     if (value == '\n') {
00092         _column = 0;
00093         _row++;
00094         if (_row >= rows()) {
00095             _row = 0;
00096         }
00097     } else {
00098         character(_column, _row, value);
00099         _column++;
00100         if (_column >= columns()) {
00101             _column = 0;
00102             _row++;
00103             if (_row >= rows()) {
00104                 _row = 0;
00105             }
00106         }
00107     }
00108     return value;
00109 }
00110 
00111 int TextLCD::_getc() {
00112     return -1;
00113 }
00114 
00115 void TextLCD::writeI2CByte(int data) {
00116     // equivalent to writeI2CByte
00117     char * cmd = new char[1];
00118     cmd[0] = data;
00119     _i2c.write(_i2cAddress, cmd, 1);
00120 }
00121 
00122 void TextLCD::writeNibble(int data, bool rs) {
00123     data<<=4;
00124     data|=8;
00125     if (rs) {
00126         data = data | RS_ON; // set rs bit
00127     }
00128     data |= E_ON; // E on
00129     writeI2CByte(data);
00130     data ^= E_ON; // E off
00131     wait_us(1);
00132     writeI2CByte(data);
00133     wait_us(1000);
00134 }
00135 
00136 void TextLCD::writeByte(int data, bool rs) {
00137     writeNibble(data >> 4, rs);
00138     writeNibble(data & 0x0F, rs);
00139 }
00140 
00141 void TextLCD::writeCommand(int command) {
00142     // equivalent to ard commandWrite
00143     writeByte(command, false);
00144 }
00145 
00146 void TextLCD::writeData(int data) {
00147 
00148     writeByte(data, true);
00149 }
00150 
00151 int TextLCD::address(int column, int row) {
00152     switch (_type) {
00153         case LCD20x4:
00154             switch (row) {
00155                 case 0:
00156                     return 0x80 + column;
00157                 case 1:
00158                     return 0xc0 + column;
00159                 case 2:
00160                     return 0x94 + column;
00161                 case 3:
00162                     return 0xd4 + column;
00163             }
00164         case LCD16x2B:
00165             return 0x80 + (row * 40) + column;
00166         case LCD16x2:
00167         case LCD20x2:
00168         default:
00169             return 0x80 + (row * 0x40) + column;
00170     }
00171 }
00172 
00173 int TextLCD::columns() {
00174     switch (_type) {
00175         case LCD20x4:
00176         case LCD20x2:
00177             return 20;
00178         case LCD16x2:
00179         case LCD16x2B:
00180         default:
00181             return 16;
00182     }
00183 }
00184 
00185 int TextLCD::rows() {
00186     switch (_type) {
00187         case LCD20x4:
00188             return 4;
00189         case LCD16x2:
00190         case LCD16x2B:
00191         case LCD20x2:
00192         default:
00193             return 2;
00194     }
00195 }