Diff: TextLCD.cpp

Revision:

0:2c5bba968d7c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TextLCD.cpp	Sun Feb 14 00:28:08 2010 +0000
@@ -0,0 +1,161 @@
+/* mbed TextLCD Library
+ * Copyright (c) 2007-2009 sford
+ * Released under the MIT License: http://mbed.org/license/mit
+ *
+ * Modified by Ned Konz to provide better support for 4-line LCDs and ones with other controller chips.
+ */
+
+#include "TextLCD.h"
+#include "mbed.h"
+
+/*
+ * 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 low except when being used.
+ * _rw is kept 0 (write) apart from actions that use 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, uint16_t rows, uint16_t cols) : _rw(rw), _rs(rs),
+        _e(e), _d(d0, d1, d2, d3), _rows(rows), _columns(cols) {
+
+    _rw = 0;
+    wait_us(1);     // min. 100nsec delay
+    _e  = 0;
+    _rs = 0;    // command mode
+    _d.output();
+
+    reset();
+    cls();
+}
+
+void TextLCD::reset() {
+    wait_ms(15);
+    // e is low at this point, as is rw.
+    // 2. Send 0x3 and wait 150 ms (will stay in 8-bit mode if already there)
+    writeHalfByte(0x3);
+    wait_ms(5);
+    // 3. Send 0x3 and wait 150 ms (will go to 8-bit mode if was in 4-bit without any garbage nibble)
+    writeHalfByte(0x3);
+    wait_ms(5);
+    // 4. Send 0x3 and wait 250 ms (will go to 8-bit mode even if garbage nibble was previously received)
+    writeHalfByte(0x3);
+    wait_ms(5);
+    // 5. Send 0x2 and wait 200 ms (should go to 4-bit mode now)
+    writeHalfByte(0x2);
+    wait_ms(5);
+    // 7. Send LCD setup sequence (eg 0x2, 0x8 (=0x28), 0x0, 0x8 (=0x08), etc.)
+    writeCommand(0x28);    // Function set 001 BW N F - -
+    wait_ms(15);
+
+    writeCommand(0x08);     // display off, cursor invisible
+    wait_ms(15);
+
+    writeCommand(0x01);
+    wait_ms(15);      // 1.64ms command
+
+    writeCommand(0x0C);     // display enabled, cursor invisible
+    wait_ms(15);
+
+    writeCommand(0x6);  //  Cursor Direction and Display Shift : 0000 01 CD S (CD 0-left, 1-right S(hift) 0-no, 1-yes
+    wait_ms(15);
+
+    locate(0,0);
+}
+
+// memory starts at 0x80, and is 0x40 chars long per row
+// However, rows 2 and 3 of 4-line displays are actually adjacent to rows 0 and 1.
+// 16x4 displays are addressed the same way as 20x4 ones.
+
+void TextLCD::character(uint16_t column, uint16_t row, int c) {
+    int address;
+    address = 0x80 + ((row & ~2) * 0x40) + column;
+    if (row > 1)
+        address += 20;
+    writeCommand(address);
+    writeData(c);
+}
+
+void TextLCD::writeHalfByte(uint16_t value) {
+    _e = 1;
+    wait_us(1);
+    _d = value & 0x0F;    // send data on bus
+    wait_us(1); // setup time
+    _e = 0; // strobe
+    wait_us(1); // hold time
+}
+
+void TextLCD::writeByte(uint16_t value) {
+    writeHalfByte(value>>4);
+    writeHalfByte(value);
+}
+
+void TextLCD::writeCommand(uint16_t command) {
+    _rs = 0;
+    writeByte(command);
+    waitUntilDone();
+}
+
+void TextLCD::writeData(uint16_t data) {
+    _rs = 1;
+    writeByte(data);
+    waitUntilDone();
+}
+
+void TextLCD::cls() {
+    writeCommand(0x01);
+    wait_us(2000);      // 1.64ms command
+    locate(0,0);
+}
+
+// This should be changed to use readAddressAndBusy() when that works.
+void TextLCD::waitUntilDone() {
+    wait_us(60);
+}
+
+// Return the busy/address byte.
+// The busy flag is the high bit.
+// Not yet working reliably.
+uint16_t TextLCD::readAddressAndBusy() {
+    _d.input();
+    _rw = 1;
+    wait_us(1);
+    _e = 1;
+    wait_us(1);
+    _e = 0;
+
+    uint16_t retval = _d.read() << 4;
+
+    wait_us(1);
+    _e = 1;
+    wait_us(1);
+    _e = 0;
+
+    retval |= _d.read();
+    _rw = 0;
+
+    _d.output();
+    return retval;
+}
+