1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
/*
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* <joerg@FreeBSD.ORG> wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
* this stuff is worth it, you can buy me a beer in return. Joerg Wunsch
* ----------------------------------------------------------------------------
*
* HD44780 LCD display driver
*
* The LCD controller is used in 4-bit mode with a full bi-directional
* interface (i.e. R/~W is connected) so the busy flag can be read.
*
* $Id: hd44780.c,v 1.3 2006/10/08 21:47:36 joerg_wunsch Exp $
*/
#include "defines.h"
#include <stdbool.h>
#include <stdint.h>
#include <avr/io.h>
#include <util/delay.h>
#include "hd44780.h"
#define GLUE(a, b) a##b
#define PORT(x) GLUE(PORT, x)
#define PIN(x) GLUE(PIN, x)
#define DDR(x) GLUE(DDR, x)
#define HD44780_PORTOUT PORT(HD44780_PORT)
#define HD44780_PORTIN PIN(HD44780_PORT)
#define HD44780_DDR DDR(HD44780_PORT)
#define HD44780_DATABITS \
(_BV(HD44780_D4)|_BV(HD44780_D5)|_BV(HD44780_D6)|_BV(HD44780_D7))
#define HD44780_BUSYFLAG 0x80
/*
* Send one pulse to the E signal (enable). Mind the timing
* constraints. If readback is set to true, read the HD44780 data
* pins right before the falling edge of E, and return that value.
*/
static inline uint8_t
hd44780_pulse_e(bool readback) __attribute__((always_inline));
static inline uint8_t
hd44780_pulse_e(bool readback)
{
uint8_t x;
HD44780_PORTOUT |= _BV(HD44780_E);
/*
* Guarantee at least 500 ns of pulse width. For high CPU
* frequencies, a delay loop is used. For lower frequencies, NOPs
* are used, and at or below 1 MHz, the native pulse width will
* already be 1 us or more so no additional delays are needed.
*/
#if F_CPU > 4000000UL
_delay_us(0.5);
#else
/*
* When reading back, we need one additional NOP, as the value read
* back from the input pin is sampled close to the beginning of a
* CPU clock cycle, while the previous edge on the output pin is
* generated towards the end of a CPU clock cycle.
*/
if (readback)
__asm__ volatile("nop");
# if F_CPU > 1000000UL
__asm__ volatile("nop");
# if F_CPU > 2000000UL
__asm__ volatile("nop");
__asm__ volatile("nop");
# endif /* F_CPU > 2000000UL */
# endif /* F_CPU > 1000000UL */
#endif
if (readback)
x = HD44780_PORTIN & HD44780_DATABITS;
else
x = 0;
HD44780_PORTOUT &= ~_BV(HD44780_E);
return x;
}
/*
* Send one nibble out to the LCD controller.
*/
static void
hd44780_outnibble(uint8_t n, uint8_t rs)
{
uint8_t x;
HD44780_PORTOUT &= ~_BV(HD44780_RW);
if (rs)
HD44780_PORTOUT |= _BV(HD44780_RS);
else
HD44780_PORTOUT &= ~_BV(HD44780_RS);
x = (HD44780_PORTOUT & ~HD44780_DATABITS) | ((n << HD44780_D4) & HD44780_DATABITS);
HD44780_PORTOUT = x;
(void)hd44780_pulse_e(false);
}
/*
* Send one byte to the LCD controller. As we are in 4-bit mode, we
* have to send two nibbles.
*/
void
hd44780_outbyte(uint8_t b, uint8_t rs)
{
hd44780_outnibble(b >> 4, rs);
hd44780_outnibble(b & 0xf, rs);
}
/*
* Read one nibble from the LCD controller.
*/
static uint8_t
hd44780_innibble(uint8_t rs)
{
uint8_t x;
HD44780_PORTOUT |= _BV(HD44780_RW);
HD44780_DDR &= ~HD44780_DATABITS;
if (rs)
HD44780_PORTOUT |= _BV(HD44780_RS);
else
HD44780_PORTOUT &= ~_BV(HD44780_RS);
x = hd44780_pulse_e(true);
HD44780_DDR |= HD44780_DATABITS;
HD44780_PORTOUT &= ~_BV(HD44780_RW);
return (x & HD44780_DATABITS) >> HD44780_D4;
}
/*
* Read one byte (i.e. two nibbles) from the LCD controller.
*/
uint8_t
hd44780_inbyte(uint8_t rs)
{
uint8_t x;
x = hd44780_innibble(rs) << 4;
x |= hd44780_innibble(rs);
return x;
}
/*
* Wait until the busy flag is cleared.
*/
void
hd44780_wait_ready(void)
{
while (hd44780_incmd() & HD44780_BUSYFLAG) ;
}
/*
* Initialize the LCD controller.
*
* The initialization sequence has a mandatory timing so the
* controller can safely recognize the type of interface desired.
* This is the only area where timed waits are really needed as
* the busy flag cannot be probed initially.
*/
void
hd44780_init(void)
{
HD44780_DDR = _BV(HD44780_RS) | _BV(HD44780_RW) | _BV(HD44780_E)
| HD44780_DATABITS;
_delay_ms(15); /* 40 ms needed for Vcc = 2.7 V */
hd44780_outnibble(HD44780_FNSET(1, 0, 0) >> 4, 0);
_delay_ms(4.1);
hd44780_outnibble(HD44780_FNSET(1, 0, 0) >> 4, 0);
_delay_ms(0.1);
hd44780_outnibble(HD44780_FNSET(1, 0, 0) >> 4, 0);
hd44780_outnibble(HD44780_FNSET(0, 1, 0) >> 4, 0);
hd44780_wait_ready();
hd44780_outcmd(HD44780_FNSET(0, 1, 0));
hd44780_wait_ready();
hd44780_outcmd(HD44780_DISPCTL(0, 0, 0));
hd44780_wait_ready();
}
|
