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
|
/*
* ----------------------------------------------------------------------------
* "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.
*
* $Id$
*/
#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.
*/
static inline void
hd44780_pulse_e(void)
{
HD44780_PORTOUT |= _BV(HD44780_E);
#if F_CPU >= 4000000UL
_delay_us(0.5); /* guarantee 500 ns high */
#elif F_CPU > 2000000UL
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
#endif
HD44780_PORTOUT &= ~_BV(HD44780_E);
}
/*
* 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_DATABITS);
HD44780_PORTOUT = x;
hd44780_pulse_e();
}
/*
* 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);
}
HD44780_PORTOUT |= _BV(HD44780_E);
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
__asm__ volatile("nop");
x = HD44780_PORTIN & HD44780_DATABITS;
HD44780_PORTOUT &= ~_BV(HD44780_E);
HD44780_DDR |= HD44780_DATABITS;
HD44780_PORTOUT &= ~_BV(HD44780_RW);
return x & HD44780_DATABITS;
}
/*
* 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)
{
// HD44780_PORTOUT = 0; // reset open drivers
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(5.1);
hd44780_outnibble(HD44780_FNSET(1, 0, 0) >> 4, 0);
_delay_ms(0.2);
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();
}
|
