1 /* $NetBSD: i2c_bitbang.c,v 1.14 2016/06/07 01:06:27 pgoyette 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/cdefs.h> 43 __KERNEL_RCSID(0, "$NetBSD: i2c_bitbang.c,v 1.14 2016/06/07 01:06:27 pgoyette Exp $"); 44 45 #include <sys/module.h> 46 #include <sys/param.h> 47 48 #include <dev/i2c/i2cvar.h> 49 #include <dev/i2c/i2c_bitbang.h> 50 51 #define SETBITS(x) ops->ibo_set_bits(v, (x)) 52 #define DIR(x) ops->ibo_set_dir(v, (x)) 53 #define READ ops->ibo_read_bits(v) 54 55 #define SDA ops->ibo_bits[I2C_BIT_SDA] /* i2c signal */ 56 #define SCL ops->ibo_bits[I2C_BIT_SCL] /* i2c signal */ 57 #define OUTPUT ops->ibo_bits[I2C_BIT_OUTPUT] /* SDA is output */ 58 #define INPUT ops->ibo_bits[I2C_BIT_INPUT] /* SDA is input */ 59 60 #ifndef SCL_BAIL_COUNT 61 #define SCL_BAIL_COUNT 1000 62 #endif 63 64 static inline int i2c_wait_for_scl(void *, i2c_bitbang_ops_t); 65 66 static inline int 67 i2c_wait_for_scl(void *v, i2c_bitbang_ops_t ops) 68 { 69 int bail = 0; 70 71 while (((READ & SCL) == 0) && (bail < SCL_BAIL_COUNT)) { 72 delay(1); 73 bail++; 74 } 75 if (bail == SCL_BAIL_COUNT) { 76 i2c_bitbang_send_stop(v, 0, ops); 77 return EIO; 78 } 79 return 0; 80 } 81 82 /*ARGSUSED*/ 83 int 84 i2c_bitbang_send_start(void *v, int flags, i2c_bitbang_ops_t ops) 85 { 86 87 /* start condition: put SDA H->L edge during SCL=H */ 88 89 DIR(OUTPUT); 90 SETBITS(SDA | SCL); 91 delay(5); /* bus free time (4.7 us) */ 92 SETBITS( 0 | SCL); 93 if (i2c_wait_for_scl(v, ops) != 0) 94 return EIO; 95 delay(4); /* start hold time (4.0 us) */ 96 97 /* leave SCL=L and SDA=L to avoid unexpected start/stop condition */ 98 SETBITS( 0 | 0); 99 100 return 0; 101 } 102 103 /*ARGSUSED*/ 104 int 105 i2c_bitbang_send_stop(void *v, int flags, i2c_bitbang_ops_t ops) 106 { 107 108 /* stop condition: put SDA L->H edge during SCL=H */ 109 110 /* assume SCL=L, SDA=L here */ 111 DIR(OUTPUT); 112 SETBITS( 0 | SCL); 113 delay(4); /* stop setup time (4.0 us) */ 114 SETBITS(SDA | SCL); 115 116 return 0; 117 } 118 119 int 120 i2c_bitbang_initiate_xfer(void *v, i2c_addr_t addr, int flags, 121 i2c_bitbang_ops_t ops) 122 { 123 124 if (addr < 0x80) { 125 uint8_t i2caddr; 126 127 /* disallow the 10-bit address prefix */ 128 if ((addr & 0x78) == 0x78) 129 return EINVAL; 130 i2caddr = (addr << 1) | ((flags & I2C_F_READ) ? 1 : 0); 131 (void) i2c_bitbang_send_start(v, flags, ops); 132 133 return (i2c_bitbang_write_byte(v, i2caddr, 134 flags & ~I2C_F_STOP, ops)); 135 136 } else if (addr < 0x400) { 137 uint16_t i2caddr; 138 int rv; 139 140 i2caddr = (addr << 1) | ((flags & I2C_F_READ) ? 1 : 0) | 141 0xf000; 142 143 (void) i2c_bitbang_send_start(v, flags, ops); 144 rv = i2c_bitbang_write_byte(v, i2caddr >> 8, 145 flags & ~I2C_F_STOP, ops); 146 /* did a slave ack the 10-bit prefix? */ 147 if (rv != 0) 148 return rv; 149 150 /* send the lower 7-bits (+ read/write mode) */ 151 return (i2c_bitbang_write_byte(v, i2caddr & 0xff, 152 flags & ~I2C_F_STOP, ops)); 153 154 } else 155 return EINVAL; 156 } 157 158 int 159 i2c_bitbang_read_byte(void *v, uint8_t *valp, int flags, i2c_bitbang_ops_t ops) 160 { 161 int i; 162 uint8_t val = 0; 163 uint32_t bit; 164 165 /* assume SCL=L, SDA=L here */ 166 167 DIR(INPUT); 168 169 for (i = 0; i < 8; i++) { 170 val <<= 1; 171 172 /* data is set at SCL H->L edge */ 173 /* SDA is set here because DIR() is INPUT */ 174 SETBITS(SDA | 0); 175 delay(5); /* clock low time (4.7 us) */ 176 177 /* read data at SCL L->H edge */ 178 SETBITS(SDA | SCL); 179 if (i2c_wait_for_scl(v, ops) != 0) 180 return EIO; 181 if (READ & SDA) 182 val |= 1; 183 delay(4); /* clock high time (4.0 us) */ 184 } 185 /* set SCL H->L before set SDA direction OUTPUT */ 186 SETBITS(SDA | 0); 187 188 /* set ack after SCL H->L edge */ 189 bit = (flags & I2C_F_LAST) ? SDA : 0; 190 DIR(OUTPUT); 191 SETBITS(bit | 0); 192 delay(5); /* clock low time (4.7 us) */ 193 194 /* ack is checked at SCL L->H edge */ 195 SETBITS(bit | SCL); 196 if (i2c_wait_for_scl(v, ops) != 0) 197 return EIO; 198 delay(4); /* clock high time (4.0 us) */ 199 200 /* set SCL H->L for next data; don't change SDA here */ 201 SETBITS(bit | 0); 202 203 /* leave SCL=L and SDA=L to avoid unexpected start/stop condition */ 204 SETBITS( 0 | 0); 205 206 207 if ((flags & (I2C_F_STOP | I2C_F_LAST)) == (I2C_F_STOP | I2C_F_LAST)) 208 (void) i2c_bitbang_send_stop(v, flags, ops); 209 210 *valp = val; 211 return 0; 212 } 213 214 int 215 i2c_bitbang_write_byte(void *v, uint8_t val, int flags, i2c_bitbang_ops_t ops) 216 { 217 uint32_t bit; 218 uint8_t mask; 219 int error; 220 221 /* assume at SCL=L, SDA=L here */ 222 223 DIR(OUTPUT); 224 225 for (mask = 0x80; mask != 0; mask >>= 1) { 226 bit = (val & mask) ? SDA : 0; 227 228 /* set data after SCL H->L edge */ 229 SETBITS(bit | 0); 230 delay(5); /* clock low time (4.7 us) */ 231 232 /* data is fetched at SCL L->H edge */ 233 SETBITS(bit | SCL); 234 if (i2c_wait_for_scl(v, ops)) 235 return EIO; 236 delay(4); /* clock high time (4.0 us) */ 237 238 /* put SCL H->L edge; don't change SDA here */ 239 SETBITS(bit | 0); 240 } 241 242 /* ack is set at H->L edge */ 243 DIR(INPUT); 244 delay(5); /* clock low time (4.7 us) */ 245 246 /* read ack at L->H edge */ 247 /* SDA is set here because DIR() is INPUT */ 248 SETBITS(SDA | SCL); 249 if (i2c_wait_for_scl(v, ops) != 0) 250 return EIO; 251 error = (READ & SDA) ? EIO : 0; 252 delay(4); /* clock high time (4.0 us) */ 253 254 /* set SCL H->L before set SDA direction OUTPUT */ 255 SETBITS(SDA | 0); 256 DIR(OUTPUT); 257 /* leave SCL=L and SDA=L to avoid unexpected start/stop condition */ 258 SETBITS( 0 | 0); 259 260 if (flags & I2C_F_STOP) 261 (void) i2c_bitbang_send_stop(v, flags, ops); 262 263 return error; 264 } 265 266 MODULE(MODULE_CLASS_MISC, i2c_bitbang, NULL); 267 268 static int 269 i2c_bitbang_modcmd(modcmd_t cmd, void *opaque) 270 { 271 272 switch (cmd) { 273 case MODULE_CMD_INIT: 274 return 0; 275 case MODULE_CMD_FINI: 276 return 0; 277 default: 278 return ENOTTY; 279 } 280 } 281
Indexes created Sat Sep 20 22:09:52 GMT 2025