i2c_bitbang.c revision 1.6
1 /* $NetBSD: i2c_bitbang.c,v 1.6 2006/11/16 01:32:50 christos Exp $ */ 2 3 /* 4 * Copyright (c) 2003 Wasabi Systems, Inc. 5 * All rights reserved. 6 * 7 * Written by Jason R. Thorpe for Wasabi Systems, Inc. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed for the NetBSD Project by 20 * Wasabi Systems, Inc. 21 * 4. The name of Wasabi Systems, Inc. may not be used to endorse 22 * or promote products derived from this software without specific prior 23 * written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC 29 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35 * POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 /* 39 * Common module for bit-bang'ing an I2C bus. 40 */ 41 42 #include <sys/param.h> 43 44 #include <dev/i2c/i2cvar.h> 45 #include <dev/i2c/i2c_bitbang.h> 46 47 #define SETBITS(x) ops->ibo_set_bits(v, (x)) 48 #define DIR(x) ops->ibo_set_dir(v, (x)) 49 #define READ ops->ibo_read_bits(v) 50 51 #define SDA ops->ibo_bits[I2C_BIT_SDA] /* i2c signal */ 52 #define SCL ops->ibo_bits[I2C_BIT_SCL] /* i2c signal */ 53 #define OUTPUT ops->ibo_bits[I2C_BIT_OUTPUT] /* SDA is output */ 54 #define INPUT ops->ibo_bits[I2C_BIT_INPUT] /* SDA is input */ 55 56 /*ARGSUSED*/ 57 int 58 i2c_bitbang_send_start(void *v, int flags, i2c_bitbang_ops_t ops) 59 { 60 61 DIR(OUTPUT); 62 63 SETBITS(SDA | SCL); 64 delay(5); /* bus free time (4.7 uS) */ 65 SETBITS( SCL); 66 delay(4); /* start hold time (4.0 uS) */ 67 SETBITS( 0); 68 delay(5); /* clock low time (4.7 uS) */ 69 70 return (0); 71 } 72 73 /*ARGSUSED*/ 74 int 75 i2c_bitbang_send_stop(void *v, int flags, i2c_bitbang_ops_t ops) 76 { 77 78 DIR(OUTPUT); 79 80 SETBITS( SCL); 81 delay(4); /* stop setup time (4.0 uS) */ 82 SETBITS(SDA | SCL); 83 84 return (0); 85 } 86 87 int 88 i2c_bitbang_initiate_xfer(void *v, i2c_addr_t addr, int flags, 89 i2c_bitbang_ops_t ops) 90 { 91 92 if (addr < 0x80) { 93 uint8_t i2caddr; 94 95 /* disallow the 10-bit address prefix */ 96 if ((addr & 0x78) == 0x78) 97 return EINVAL; 98 i2caddr = (addr << 1) | ((flags & I2C_F_READ) ? 1 : 0); 99 (void) i2c_bitbang_send_start(v, flags, ops); 100 101 return (i2c_bitbang_write_byte(v, i2caddr, 102 flags & ~I2C_F_STOP, ops)); 103 104 } else if (addr < 0x400) { 105 uint16_t i2caddr; 106 int rv; 107 108 i2caddr = (addr << 1) | ((flags & I2C_F_READ) ? 1 : 0) | 109 0xf000; 110 111 (void) i2c_bitbang_send_start(v, flags, ops); 112 rv = i2c_bitbang_write_byte(v, i2caddr >> 8, 113 flags & ~I2C_F_STOP, ops); 114 /* did a slave ack the 10-bit prefix? */ 115 if (rv != 0) 116 return rv; 117 118 /* send the lower 7-bits (+ read/write mode) */ 119 return (i2c_bitbang_write_byte(v, i2caddr & 0xff, 120 flags & ~I2C_F_STOP, ops)); 121 122 } else 123 return EINVAL; 124 } 125 126 int 127 i2c_bitbang_read_byte(void *v, uint8_t *valp, int flags, 128 i2c_bitbang_ops_t ops) 129 { 130 int i; 131 uint8_t val = 0; 132 uint32_t bit; 133 134 DIR(INPUT); 135 SETBITS(SDA ); 136 137 for (i = 0; i < 8; i++) { 138 val <<= 1; 139 SETBITS(SDA | SCL); 140 delay(4); /* clock high time (4.0 uS) */ 141 if (READ & SDA) 142 val |= 1; 143 SETBITS(SDA ); 144 delay(5); /* clock low time (4.7 uS) */ 145 } 146 147 bit = (flags & I2C_F_LAST) ? SDA : 0; 148 DIR(OUTPUT); 149 SETBITS(bit ); 150 delay(1); /* data setup time (250 nS) */ 151 SETBITS(bit | SCL); 152 delay(4); /* clock high time (4.0 uS) */ 153 SETBITS(bit ); 154 delay(5); /* clock low time (4.7 uS) */ 155 156 DIR(INPUT); 157 SETBITS(SDA ); 158 delay(5); 159 160 if ((flags & (I2C_F_STOP | I2C_F_LAST)) == (I2C_F_STOP | I2C_F_LAST)) 161 (void) i2c_bitbang_send_stop(v, flags, ops); 162 163 *valp = val; 164 return (0); 165 } 166 167 int 168 i2c_bitbang_write_byte(void *v, uint8_t val, int flags, 169 i2c_bitbang_ops_t ops) 170 { 171 uint32_t bit; 172 uint8_t mask; 173 int error; 174 175 DIR(OUTPUT); 176 177 for (mask = 0x80; mask != 0; mask >>= 1) { 178 bit = (val & mask) ? SDA : 0; 179 SETBITS(bit ); 180 delay(1); /* data setup time (250 nS) */ 181 SETBITS(bit | SCL); 182 delay(4); /* clock high time (4.0 uS) */ 183 SETBITS(bit ); 184 delay(5); /* clock low time (4.7 uS) */ 185 } 186 187 DIR(INPUT); 188 189 SETBITS(SDA ); 190 delay(5); 191 SETBITS(SDA | SCL); 192 delay(4); 193 error = (READ & SDA) ? EIO : 0; 194 SETBITS(SDA ); 195 delay(5); 196 197 if (flags & I2C_F_STOP) 198 (void) i2c_bitbang_send_stop(v, flags, ops); 199 200 return (error); 201 } 202
Indexes created Mon Sep 22 13:09:51 GMT 2025