WattBob_TextLCD.cpp

00001 /* draft mbed TextLCD 
00002  * (c) 2007/8, sford
00003  * Modified jherd
00004  */
00005  
00006 #include "WattBob_TextLCD.h"
00007 #include "MCP23017.h"
00008 
00009 #include "mbed.h"
00010 
00011 /*
00012  * Initialisation
00013  * ==============
00014  *
00015  * After attaching the supply voltage/after a reset, the display needs to be brought in to a defined state
00016  *
00017  * - wait approximately 15 ms so the display is ready to execute commands
00018  * - Execute the command 0x30 ("Display Settings") three times (wait 1,64ms after each command, the busy flag cannot be queried now). 
00019  * - 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.
00020  * - If you want to use the 4 bit mode, now you can execute the command to switch over to this mode now.
00021  * - Execute the "clear display" command
00022  *
00023  * Timing
00024  * ======
00025  *
00026  * Nearly all commands transmitted to the display need 40us for execution. 
00027  * Exceptions are the commands "Clear Display and Reset" and "Set Cursor to Start Position" 
00028  * These commands need 1.64ms for execution. These timings are valid for all displays working with an 
00029  * internal clock of 250kHz. But I do not know any displays that use other frequencies. Any time you 
00030  * can use the busy flag to test if the display is ready to accept the next command.
00031  * 
00032  * _e is kept high apart from calling clock
00033  * _rw is kept 0 (write) apart from actions that uses it differently
00034  * _rs is set by the data/command writes
00035  * 
00036  * RS = 7
00037  * RW = 6
00038  * E  = 5
00039  * Back light = 4
00040  * D4 = 0
00041  * D5 = 1  
00042  * D6 = 2
00043  * D7 = 3  
00044  */
00045 
00046 WattBob_TextLCD::WattBob_TextLCD(MCP23017 *port) {
00047 //
00048 // Initialise pointer to MCP23017 object
00049 //
00050     par_port = port;
00051     par_port->config(0x0F00, 0x0F00, 0x0F00);
00052     
00053     _rows = 2;
00054     _columns = 16;
00055 
00056     // 
00057     // Time to allow unit to initialise
00058     //
00059      wait(DISPLAY_INIT_DELAY_SECS); 
00060      
00061     _rw(0);
00062     _e(0);
00063     _rs(0); // command mode
00064     
00065     //
00066     // interface defaults to an 8-bit interface. However, we need to ensure that we
00067     // are in 8-bit mode
00068     //   
00069     for(int i=0; i<3; i++) {
00070         writeNibble(CMD4_SET_8_BIT_INTERFACE);
00071         wait(0.00164);      // this command takes 1.64ms, so wait for it
00072     }
00073     
00074     writeNibble(CMD4_SET_4_BIT_INTERFACE);       // now force into 4-bit mode   
00075     
00076 //    writeCommand(CMD_NULL);
00077 //    writeCommand(CMD_NULL);
00078 //    writeCommand(CMD_NULL);
00079 //    writeCommand(CMD_NULL);
00080 //    writeCommand(CMD_NULL);
00081           
00082     writeCommand(CMD_FUNCTION_SET | INTERFACE_4_BIT | TWO_LINE_DISPLAY | FONT_5x8 | ENGL_JAPAN_FONT_SET); //  0x28
00083     writeCommand(CMD_DISPLAY_CONTROL | DISPLAY_ON | CURSOR_OFF | CURSOR_CHAR_BLINK_OFF); // 0xC0
00084     cls();
00085     writeCommand(CMD_RETURN_HOME);    
00086     writeCommand(CMD_ENTRY_MODE | CURSOR_STEP_RIGHT | DISPLAY_SHIFT_OFF );  // 0x06
00087 }
00088 
00089 int WattBob_TextLCD::_putc(int value) {
00090     if(value == '\n') {
00091         newline();
00092     } else {
00093         writeData(value);
00094     }
00095     return value;
00096 }
00097 
00098 int WattBob_TextLCD::_getc() {
00099     return 0;
00100 }
00101 
00102 void WattBob_TextLCD::newline() {
00103     _column = 0;
00104     _row++;
00105     if(_row >= _rows) {
00106         _row = 0;
00107     }
00108     locate(_column, _row); 
00109 }
00110 
00111 void WattBob_TextLCD::locate(int row, int column) {
00112     if(column < 0 || column >= _columns || row < 0 || row >= _rows) {
00113         // error("locate(%d,%d) out of range on %dx%d display", column, row, _columns, _rows);
00114         return;
00115     }
00116     
00117     _row = row;
00118     _column = column;
00119     int address = 0x80 + (_row * 0x40) + _column; // memory starts at 0x80, and internally it is 40 chars per row (only first 16 used)
00120     writeCommand(address);            
00121 }
00122 
00123 void WattBob_TextLCD::cls() {
00124     writeCommand(CMD_CLEAR_DISPLAY);  // 0x01
00125     wait(DISPLAY_CLEAR_DELAY);                    // 
00126     locate(0, 0);
00127 }
00128 
00129 void WattBob_TextLCD::reset() {
00130     cls();
00131 }
00132 
00133 void WattBob_TextLCD::clock() {
00134     wait(0.000040f);
00135     _e(1);
00136     wait(0.000040f);  // most instructions take 40us
00137     _e(0);    
00138 }
00139 
00140 void WattBob_TextLCD::writeNibble(int value) {
00141     _d(value);
00142     clock();
00143 }
00144 
00145 void WattBob_TextLCD::writeByte(int value) {
00146     writeNibble((value >> 4) & 0x000F);
00147     writeNibble((value >> 0) & 0x000F);
00148 }
00149 
00150 void WattBob_TextLCD::writeCommand(int command) {
00151     _rs(0);
00152     writeByte(command);
00153 }
00154 
00155 void WattBob_TextLCD::writeData(int data) {
00156     _rs(1);
00157     writeByte(data);
00158     _column++;
00159     if(_column >= _columns) {
00160         newline();
00161     } 
00162 }
00163 
00164 void WattBob_TextLCD::_rs(int data) {
00165     par_port->write_bit(data, RS_BIT);
00166 }
00167 
00168 void WattBob_TextLCD::_rw(int data) {
00169     par_port->write_bit(data, RW_BIT);
00170 }
00171 
00172 void WattBob_TextLCD::_e(int data) {
00173     par_port->write_bit(data, E_BIT);
00174 }
00175 
00176 void WattBob_TextLCD::_d(int data) {
00177     par_port->write_mask((unsigned short)data, (unsigned short)0x000F);
00178 }
00179