tmk_core/protocol/lufa/LUFA-git/Projects/SerialToLCD/Lib/HD44780.c

   1 /*
   2              LUFA Library
   3      Copyright (C) Dean Camera, 2014.
   4
   5   dean [at] fourwalledcubicle [dot] com
   6            www.lufa-lib.org
   7 */
   8
   9 /*
  10   Copyright 2014  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  11   Copyright 2012  Simon Foster (simon.foster [at] inbox [dot] com)
  12
  13   Permission to use, copy, modify, distribute, and sell this
  14   software and its documentation for any purpose is hereby granted
  15   without fee, provided that the above copyright notice appear in
  16   all copies and that both that the copyright notice and this
  17   permission notice and warranty disclaimer appear in supporting
  18   documentation, and that the name of the author not be used in
  19   advertising or publicity pertaining to distribution of the
  20   software without specific, written prior permission.
  21
  22   The author disclaims all warranties with regard to this
  23   software, including all implied warranties of merchantability
  24   and fitness.  In no event shall the author be liable for any
  25   special, indirect or consequential damages or any damages
  26   whatsoever resulting from loss of use, data or profits, whether
  27   in an action of contract, negligence or other tortious action,
  28   arising out of or in connection with the use or performance of
  29   this software.
  30 */
  31
  32 #include "HD44780.h"
  33
  34 static void HD44780_WriteNibble(const uint8_t nib)
  35 {
  36         /* Read PORTD and clear the ENABLE and PD0..3 bits
  37            then OR in the data */
  38
  39         PORTD = (PORTD & ~(ENABLE | LO4_MASK)) | (nib & LO4_MASK);
  40
  41         /* Enforce address setup time (tAS) 60ns
  42            60 @ 16MHz = <1
  43            Let's us a few NOPs for good measure */
  44         asm volatile("nop\n\t"
  45                      "nop\n\t"
  46                      :: );
  47
  48         /* Take enable high and enforce Enable High time (tEH=450ns)
  49            450ns @ 16MHz = 7.2 => 7 NOPs */
  50
  51         PORTD |= ENABLE;
  52
  53         asm volatile("nop\n\t"
  54                      "nop\n\t"
  55                      "nop\n\t"
  56                      "nop\n\t"
  57                      "nop\n\t"
  58                      "nop\n\t"
  59                      "nop\n\t"
  60                      "nop\n\t"
  61                      :: );
  62
  63         /* Take enable low and enforce Enable Low time (tEL=500ns)
  64            500ns @ 16MHz = 8.0 => 7 NOPs */
  65         PORTD &= ~ENABLE;
  66
  67         asm volatile("nop\n\t"
  68                      "nop\n\t"
  69                      "nop\n\t"
  70                      "nop\n\t"
  71                      "nop\n\t"
  72                      "nop\n\t"
  73                      "nop\n\t"
  74                      "nop\n\t"
  75                      :: );
  76 }
  77
  78 static void HD44780_WriteByte(const uint8_t c)
  79 {
  80         HD44780_WriteNibble(HI4(c));
  81         HD44780_WriteNibble(LO4(c));
  82 }
  83
  84 static void HD44780_PowerUp4Bit(void)
  85 {
  86         /* Wait for more than 40 ms after VCC rises to 2.7 V */
  87         _delay_ms(40);
  88         HD44780_WriteNibble(0x03);        // FN_SET 8-bit
  89
  90         /* Wait for more than 4.1 ms */
  91         _delay_ms(5);
  92         HD44780_WriteNibble(0x03);        // FN_SET 8-bit
  93
  94         /* Wait for more than 100 µs */
  95         _delay_us(100);
  96         HD44780_WriteNibble(0x03);        // FN_SET 8-bit
  97
  98         /* From now on we must allow 40us for each command */
  99         _delay_us(50);
 100         HD44780_WriteNibble(0x02);        // FN_SET 4-bit
 101
 102         /* The LCD is now in 4-bit mode so we can continue
 103            using the 4-bit API */
 104         _delay_us(50);
 105 }
 106
 107 void HD44780_Initialize(void)
 108 {
 109         PORTD &= ~ALL_BITS;
 110         DDRD  |=  ALL_BITS;
 111         HD44780_PowerUp4Bit();
 112 }
 113
 114 void HD44780_WriteCommand(const uint8_t c)
 115 {
 116         PORTD &= ~RS;
 117         HD44780_WriteByte(c);
 118         _delay_us(50);
 119 }
 120
 121 void HD44780_WriteData(const uint8_t c)
 122 {
 123         PORTD |=  RS;
 124         HD44780_WriteByte(c);
 125         PORTD &= ~RS;
 126         _delay_us(50);
 127 }