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
|
/* Bit-banging I2C layer, inspired to a large extent from Linux kernel
* i2c-algo-bit.c code (C) 1995-2000 Simon G. Vogl. This particular
* implementation is (C) 2019 by Harald Welte <laforge@gnumonks.org>
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include <hal_gpio.h>
#include <hal_delay.h>
#include <err_codes.h>
#include "i2c_bitbang.h"
#define setsda(adap, val) gpio_set_pin_level((adap)->pin_sda, val)
#define setscl(adap, val) gpio_set_pin_level((adap)->pin_scl, val)
static int getsda(const struct i2c_adapter *adap)
{
int rc;
gpio_set_pin_direction(adap->pin_sda, GPIO_DIRECTION_IN);
rc = gpio_get_pin_level(adap->pin_sda);
gpio_set_pin_direction(adap->pin_sda, GPIO_DIRECTION_OUT);
return rc;
}
static int getscl(const struct i2c_adapter *adap)
{
int rc;
gpio_set_pin_direction(adap->pin_scl, GPIO_DIRECTION_IN);
rc = gpio_get_pin_level(adap->pin_scl);
gpio_set_pin_direction(adap->pin_scl, GPIO_DIRECTION_OUT);
return rc;
}
static inline void sdalo(const struct i2c_adapter *adap)
{
setsda(adap, 0);
delay_us((adap->udelay+1) / 2);
}
static inline void sdahi(const struct i2c_adapter *adap)
{
setsda(adap, 1);
delay_us((adap->udelay+1) / 2);
}
static inline void scllo(const struct i2c_adapter *adap)
{
setscl(adap, 0);
delay_us(adap->udelay / 2);
}
static int sclhi(const struct i2c_adapter *adap)
{
setscl(adap, 1);
/* wait for slow slaves' clock stretching to complete */
while (!getscl(adap)) {
/* FIXME: abort at some point */
}
return 0;
}
static void i2c_start(const struct i2c_adapter *adap)
{
/* Assert: SCL + SDA are high */
setsda(adap, 0); /* set SDA to low */
delay_us(adap->udelay); /* delay */
scllo(adap); /* Set SCL to low */
}
static void i2c_repstart(const struct i2c_adapter *adap)
{
/* Assert: SCL is low */
sdahi(adap);
sclhi(adap);
setsda(adap, 0);
delay_us(adap->udelay);
scllo(adap);
}
static void i2c_stop(const struct i2c_adapter *adap)
{
/* Assert: SCL is low */
sdalo(adap); /* set SDA low */
sclhi(adap); /* set SCL to high */
setsda(adap, 1); /* set SDA to high */
delay_us(adap->udelay); /* delay */
}
static int i2c_outb(const struct i2c_adapter *adap, uint8_t outdata)
{
uint8_t sb;
int ack, i;
/* Assert: SCL is low */
for (i = 7; i >= 0; i--) {
sb = (outdata >> i) & 1;
setsda(adap, sb);
delay_us((adap->udelay + 1) / 2);
if (sclhi(adap) < 0)
return -ERR_TIMEOUT;
scllo(adap);
}
sdahi(adap);
if (sclhi(adap) < 0)
return -ERR_TIMEOUT;
ack = !getsda(adap);
scllo(adap);
return ack;
}
static int i2c_inb(const struct i2c_adapter *adap)
{
uint8_t indata = 0;
int i;
/* Assert: CSL is low */
sdahi(adap);
for (i = 0; i < 8; i++) {
/* SCL high */
if (sclhi(adap) < 0)
return -ERR_TIMEOUT;
indata = indata << 1;
if (getsda(adap))
indata |= 0x01;
setscl(adap, 0);
if (i == 7)
delay_us(adap->udelay / 2);
else
delay_us(adap->udelay);
}
/* Assert: SCL is low */
return indata;
}
/*! Single-byte register write. Assumes 8bit register address + 8bit values */
int i2c_write_reg(const struct i2c_adapter *adap, uint8_t addr, uint8_t reg, uint8_t val)
{
int rc;
i2c_start(adap);
rc = i2c_outb(adap, addr << 1);
if (rc < 0)
goto out_stop;
rc = i2c_outb(adap, reg);
if (rc < 0)
goto out_stop;
rc = i2c_outb(adap, val);
out_stop:
i2c_stop(adap);
return rc;
}
/*! Single-byte register read. Assumes 8bit register address + 8bit values */
int i2c_read_reg(const struct i2c_adapter *adap, uint8_t addr, uint8_t reg)
{
int rc;
i2c_start(adap);
rc = i2c_outb(adap, addr << 1);
if (rc < 0)
goto out_stop;
rc = i2c_outb(adap, reg);
if (rc < 0)
goto out_stop;
i2c_repstart(adap);
rc = i2c_outb(adap, addr << 1 | 1);
if (rc < 0)
goto out_stop;
rc = i2c_inb(adap);
out_stop:
i2c_stop(adap);
return rc;
}
/*! Initialize a given I2C adapter/bus */
int i2c_init(const struct i2c_adapter *adap)
{
gpio_set_pin_direction(adap->pin_sda, GPIO_DIRECTION_OUT);
gpio_set_pin_direction(adap->pin_scl, GPIO_DIRECTION_OUT);
/* Bring bus to a known state. Looks like STOP if bus is not free yet */
setscl(adap, 1);
delay_us(adap->udelay);
setsda(adap, 1);
return 0;
}
|
