File content as of revision 0:8e3468376286:
/* draft mbed TextLCD
* (c) 2007/8, sford
*/
#include "TextLCD.h"
#include "mbed.h"
using namespace mbed;
/*
* useful info found at http://www.a-netz.de/lcd.en.php
*
*
* Initialisation
* ==============
*
* After attaching the supply voltage/after a reset, the display needs to be brought in to a defined state
*
* - wait approximately 15 ms so the display is ready to execute commands
* - Execute the command 0x30 ("Display Settings") three times (wait 1,64ms after each command, the busy flag cannot be queried now).
* - 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.
* - If you want to use the 4 bit mode, now you can execute the command to switch over to this mode now.
* - Execute the "clear display" command
*
* Timing
* ======
*
* Nearly all commands transmitted to the display need 40us for execution.
* Exceptions are the commands "Clear Display and Reset" and "Set Cursor to Start Position"
* These commands need 1.64ms for execution. These timings are valid for all displays working with an
* internal clock of 250kHz. But I do not know any displays that use other frequencies. Any time you
* can use the busy flag to test if the display is ready to accept the next command.
*
* _e is kept high apart from calling clock
* _rw is kept 0 (write) apart from actions that uyse it differently
* _rs is set by the data/command writes
*/
TextLCD::TextLCD(PinName rs, PinName rw, PinName e, PinName d0, PinName d1,
PinName d2, PinName d3) : _rw(rw), _rs(rs),
_e(e), _d(d0, d1, d2, d3){
_rows = 4;
_columns = 20;
_rw = 0;
_e = 1;
_rs = 0; // command mode
// Should theoretically wait 15ms, but most things will be powered up pre-reset
// so i'll disable that for the minute. If implemented, could wait 15ms post reset
// instead
// wait(0.015);
// send "Display Settings" 3 times (Only top nibble of 0x30 as we've got 4-bit bus)
for(int i=0; i<3; i++) {
writeNibble(0x3);
wait(0.00164); // this command takes 1.64ms, so wait for it
}
writeNibble(0x2); // 4-bit mode
writeCommand(0x28); // Function set 001 BW N F - -
writeCommand(0x0C);
writeCommand(0x6); // Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
cls();
}
int TextLCD::_putc(int value) {
if(value == '\n') {
newline();
} else {
writeData(value);
}
return value;
}
int TextLCD::_getc() {
return 0;
}
void TextLCD::newline() {
_column = 0;
_row++;
if(_row >= _rows) {
_row = 0;
}
locate(_column, _row);
}
void TextLCD::locate(int column, int row) {
if(column < 0 || column >= _columns || row < 0 || row >= _rows) {
error("locate(%d,%d) out of range on %dx%d display", column, row, _columns, _rows);
return;
}
_row = row;
_column = column;
int address=0;
// row 0 : 0x0->0x13
// row 1 : 0x40->0x53
// row 2 : 0x14->0x27
// row 3 : 0x54->0x67
switch (_row) {
case (0) : address = 0x00 + _column;
break;
case (1) : address = 0x40 + _column;
break;
case (2) : address = 0x14 + _column;
break;
case (3) : address = 0x54 + _column;
break;
}
address += 0x80;
// }
// else {
// memory starts at 0x80, and is 40 chars long per row
// address = 0x80 + (_row * 40) + _column;
// }
writeCommand(address);
}
void TextLCD::rows(int rows) {
_rows = rows;
}
void TextLCD::columns(int columns) {
_columns = columns;
}
void TextLCD::cls() {
writeCommand(0x01); // Clear Display
wait(0.00164f); // This command takes 1.64 ms
locate(0, 0);
}
void TextLCD::reset() {
cls();
}
void TextLCD::clock() {
wait(0.000040f);
_e = 0;
wait(0.000040f); // most instructions take 40us
_e = 1;
}
void TextLCD::writeNibble(int value) {
_d = value;
clock();
}
void TextLCD::writeByte(int value) {
writeNibble(value >> 4);
writeNibble(value >> 0);
}
void TextLCD::writeCommand(int command) {
_rs = 0;
writeByte(command);
}
void TextLCD::writeData(int data) {
_rs = 1;
writeByte(data);
_column++;
if(_column >= _columns) {
newline();
}
}