1 /* $OpenBSD: i2c_bitbang.c,v 1.5 2023/03/08 04:43:08 guenther Exp $ */
2 /* $NetBSD: i2c_bitbang.c,v 1.1 2003/09/30 00:35:31 thorpej Exp $ */
3
4 /*
5 * Copyright (c) 2003 Wasabi Systems, Inc.
6 * All rights reserved.
7 *
8 * Written by Jason R. Thorpe for Wasabi Systems, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed for the NetBSD Project by
21 * Wasabi Systems, Inc.
22 * 4. The name of Wasabi Systems, Inc. may not be used to endorse
23 * or promote products derived from this software without specific prior
24 * written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39 /*
40 * Common module for bit-bang'ing an I2C bus.
41 */
42
43 #include <sys/param.h>
44
45 #include <dev/i2c/i2cvar.h>
46 #include <dev/i2c/i2c_bitbang.h>
47
48 #define BB_SET(x) ops->ibo_set_bits(v, (x))
49 #define BB_DIR(x) ops->ibo_set_dir(v, (x))
50 #define BB_READ ops->ibo_read_bits(v)
51
52 #define SDA ops->ibo_bits[I2C_BIT_SDA] /* i2c signal */
53 #define SCL ops->ibo_bits[I2C_BIT_SCL] /* i2c signal */
54 #define OUTPUT ops->ibo_bits[I2C_BIT_OUTPUT] /* SDA is output */
55 #define INPUT ops->ibo_bits[I2C_BIT_INPUT] /* SDA is input */
56
57 #define SCL_BAIL_COUNT 1000
58
59 int i2c_wait_for_scl(void *, i2c_bitbang_ops_t);
60
61 int
i2c_wait_for_scl(void * v,i2c_bitbang_ops_t ops)62 i2c_wait_for_scl(void *v, i2c_bitbang_ops_t ops)
63 {
64 int bail = 0;
65
66 while(((BB_READ & SCL) == 0) && bail < SCL_BAIL_COUNT) {
67 delay(1);
68 bail++;
69 }
70 if (bail == SCL_BAIL_COUNT) {
71 i2c_bitbang_send_stop(v, 0, ops);
72 return (EIO);
73 }
74
75 return (0);
76 }
77
78 int
i2c_bitbang_send_start(void * v,int flags,i2c_bitbang_ops_t ops)79 i2c_bitbang_send_start(void *v, int flags, i2c_bitbang_ops_t ops)
80 {
81
82 BB_DIR(OUTPUT);
83
84 BB_SET(SDA | SCL);
85 delay(5); /* bus free time (4.7 uS) */
86 BB_SET( SCL);
87 if (i2c_wait_for_scl(v, ops) != 0)
88 return (EIO);
89 delay(4); /* start hold time (4.0 uS) */
90 BB_SET( 0);
91 delay(5); /* clock low time (4.7 uS) */
92
93 return (0);
94 }
95
96 int
i2c_bitbang_send_stop(void * v,int flags,i2c_bitbang_ops_t ops)97 i2c_bitbang_send_stop(void *v, int flags, i2c_bitbang_ops_t ops)
98 {
99
100 BB_DIR(OUTPUT);
101
102 BB_SET( SCL);
103 delay(4); /* stop setup time (4.0 uS) */
104 BB_SET(SDA | SCL);
105
106 return (0);
107 }
108
109 int
i2c_bitbang_initiate_xfer(void * v,i2c_addr_t addr,int flags,i2c_bitbang_ops_t ops)110 i2c_bitbang_initiate_xfer(void *v, i2c_addr_t addr, int flags,
111 i2c_bitbang_ops_t ops)
112 {
113 int i2caddr;
114
115 /* XXX Only support 7-bit addressing for now. */
116 if ((addr & 0x78) == 0x78)
117 return (EINVAL);
118
119 i2caddr = (addr << 1) | ((flags & I2C_F_READ) ? 1 : 0);
120
121 (void) i2c_bitbang_send_start(v, flags, ops);
122 return (i2c_bitbang_write_byte(v, i2caddr, flags & ~I2C_F_STOP, ops));
123 }
124
125 int
i2c_bitbang_read_byte(void * v,uint8_t * valp,int flags,i2c_bitbang_ops_t ops)126 i2c_bitbang_read_byte(void *v, uint8_t *valp, int flags,
127 i2c_bitbang_ops_t ops)
128 {
129 int i;
130 uint8_t val = 0;
131 uint32_t bit;
132
133 BB_DIR(INPUT);
134 BB_SET(SDA );
135
136 for (i = 0; i < 8; i++) {
137 val <<= 1;
138 BB_SET(SDA | SCL);
139 if (i2c_wait_for_scl(v, ops) != 0)
140 return (EIO);
141 delay(4); /* clock high time (4.0 uS) */
142 if (BB_READ & SDA)
143 val |= 1;
144 BB_SET(SDA );
145 delay(5); /* clock low time (4.7 uS) */
146 }
147
148 bit = (flags & I2C_F_LAST) ? SDA : 0;
149 BB_DIR(OUTPUT);
150 BB_SET(bit );
151 delay(1); /* data setup time (250 nS) */
152 BB_SET(bit | SCL);
153 if (i2c_wait_for_scl(v, ops) != 0)
154 return (EIO);
155 delay(4); /* clock high time (4.0 uS) */
156 BB_SET(bit );
157 delay(5); /* clock low time (4.7 uS) */
158
159 BB_DIR(INPUT);
160 BB_SET(SDA );
161 delay(5);
162
163 if ((flags & (I2C_F_STOP | I2C_F_LAST)) == (I2C_F_STOP | I2C_F_LAST))
164 (void) i2c_bitbang_send_stop(v, flags, ops);
165
166 *valp = val;
167 return (0);
168 }
169
170 int
i2c_bitbang_write_byte(void * v,uint8_t val,int flags,i2c_bitbang_ops_t ops)171 i2c_bitbang_write_byte(void *v, uint8_t val, int flags,
172 i2c_bitbang_ops_t ops)
173 {
174 uint32_t bit;
175 uint8_t mask;
176 int error;
177
178 BB_DIR(OUTPUT);
179
180 for (mask = 0x80; mask != 0; mask >>= 1) {
181 bit = (val & mask) ? SDA : 0;
182 BB_SET(bit );
183 delay(1); /* data setup time (250 nS) */
184 BB_SET(bit | SCL);
185 if (i2c_wait_for_scl(v, ops) != 0)
186 return (EIO);
187 delay(4); /* clock high time (4.0 uS) */
188 BB_SET(bit );
189 delay(5); /* clock low time (4.7 uS) */
190 }
191
192 BB_DIR(INPUT);
193
194 BB_SET(SDA );
195 delay(5);
196 BB_SET(SDA | SCL);
197 if (i2c_wait_for_scl(v, ops) != 0)
198 return (EIO);
199 delay(4);
200 error = (BB_READ & SDA) ? EIO : 0;
201 BB_SET(SDA );
202 delay(5);
203
204 if (flags & I2C_F_STOP)
205 (void) i2c_bitbang_send_stop(v, flags, ops);
206
207 return (error);
208 }
209