Mercurial > ~darius > hgwebdir.cgi > tempctrl
annotate 1wire.c @ 43:51e7458d2e76
Init lastdata same as lastheat/coolon/off otherwise we won't handle thing
properly early on (ie if now < lastdata/lastheat/coolon/off)
| author | darius@inchoate.localdomain |
|---|---|
| date | Sun, 06 Jul 2008 22:42:32 +0930 |
| parents | 5898fba6593c |
| children | efd44dc40934 |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 * Various 1 wire routines | |
| 12 | 3 * Search routine is copied from the Dallas owpd library with mods |
| 4 * available from here http://www.ibutton.com/software/1wire/wirekit.html | |
| 0 | 5 * |
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6 * $Id$ |
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7 * |
| 0 | 8 * Copyright (c) 2004 |
| 9 * Daniel O'Connor <darius@dons.net.au>. All rights reserved. | |
| 10 * | |
| 11 * Redistribution and use in source and binary forms, with or without | |
| 12 * modification, are permitted provided that the following conditions | |
| 13 * are met: | |
| 14 * 1. Redistributions of source code must retain the above copyright | |
| 15 * notice, this list of conditions and the following disclaimer. | |
| 16 * 2. Redistributions in binary form must reproduce the above copyright | |
| 17 * notice, this list of conditions and the following disclaimer in the | |
| 18 * documentation and/or other materials provided with the distribution. | |
| 19 * | |
| 20 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND | |
| 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 23 * ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE | |
| 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
| 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
| 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
| 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
| 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| 30 * SUCH DAMAGE. | |
| 31 */ | |
| 32 | |
|
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33 /* |
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34 * No user servicable parts inside |
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35 * |
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36 * Modify 1wire-config.h |
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37 */ |
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38 |
| 0 | 39 #include <stdio.h> |
| 40 #include <avr/io.h> | |
| 41 #include <avr/pgmspace.h> | |
| 21 | 42 #include <util/delay.h> |
| 0 | 43 #include "1wire.h" |
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44 #include "1wire-config.h" |
| 41 | 45 #include "cons.h" |
| 0 | 46 |
| 47 static uint8_t OW_LastDevice = 0; | |
| 48 static uint8_t OW_LastDiscrepancy = 0; | |
| 49 static uint8_t OW_LastFamilyDiscrepancy = 0; | |
| 50 | |
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51 /*----------------------------------------------------------------------------- |
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52 * Configure the IO port as we need |
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53 */ |
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54 void |
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55 OWInit(void) { |
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56 OWBUSINIT(); |
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57 OWSETBUSHIGH(); |
| 0 | 58 } |
| 59 | |
| 60 /*----------------------------------------------------------------------------- | |
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61 * Generate a 1-Wire reset, return 0 if presence pulse was found, 1 if it |
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62 * wasn't, or 2 if the line appears to be being held low. |
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63 * |
| 0 | 64 * (NOTE: Does not handle alarm presence from DS2404/DS1994) |
| 65 */ | |
| 12 | 66 uint8_t |
| 0 | 67 OWTouchReset(void) { |
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68 OWDELAY_G; |
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69 |
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70 /* Check the bus isn't being held low (ie it's broken) Do it after |
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71 * the delay so we guarantee we don't see a slave from a previous |
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72 * comms attempt |
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73 */ |
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74 if(OWREADBUS() == 0) |
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75 return 2; |
| 0 | 76 |
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77 OWSETBUSLOW(); |
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78 OWDELAY_H; |
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79 OWSETBUSHIGH(); |
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80 OWDELAY_I; |
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81 |
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82 return(OWREADBUS()); |
| 0 | 83 } |
| 84 | |
| 85 /*----------------------------------------------------------------------------- | |
| 86 * Send a 1-wire write bit. | |
| 87 */ | |
| 88 void | |
| 12 | 89 OWWriteBit(uint8_t bit) { |
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90 OWDELAY_I; |
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91 |
| 0 | 92 if (bit) { |
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93 OWSETBUSLOW(); |
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94 OWDELAY_A; |
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95 OWSETBUSHIGH(); |
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96 OWDELAY_B; |
| 0 | 97 } else { |
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98 OWSETBUSLOW(); |
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99 OWDELAY_C; |
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100 OWSETBUSHIGH(); |
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101 OWDELAY_D; |
| 0 | 102 } |
| 103 } | |
| 104 | |
| 105 /*----------------------------------------------------------------------------- | |
| 106 * Read a bit from the 1-wire bus and return it. | |
| 107 */ | |
| 12 | 108 uint8_t |
| 0 | 109 OWReadBit(void) { |
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110 OWDELAY_I; |
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111 |
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112 OWSETBUSLOW(); |
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113 OWDELAY_A; |
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114 OWSETBUSHIGH(); |
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115 OWDELAY_E; |
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116 return(OWREADBUS()); |
| 0 | 117 } |
| 118 | |
| 119 /*----------------------------------------------------------------------------- | |
| 120 * Write a byte to the 1-wire bus | |
| 121 */ | |
| 122 void | |
| 123 OWWriteByte(uint8_t data) { | |
| 12 | 124 uint8_t i; |
| 0 | 125 |
| 126 /* Send LSB first */ | |
| 127 for (i = 0; i < 8; i++) { | |
| 128 OWWriteBit(data & 0x01); | |
| 129 data >>= 1; | |
| 130 } | |
| 131 } | |
| 132 | |
| 133 /*----------------------------------------------------------------------------- | |
| 134 * Read a byte from the 1-wire bus | |
| 135 */ | |
| 12 | 136 uint8_t |
| 0 | 137 OWReadByte(void) { |
| 138 int i, result = 0; | |
| 139 | |
| 140 for (i = 0; i < 8; i++) { | |
| 141 result >>= 1; | |
| 142 if (OWReadBit()) | |
| 143 result |= 0x80; | |
| 144 } | |
| 145 return(result); | |
| 146 } | |
| 147 | |
| 148 /*----------------------------------------------------------------------------- | |
| 149 * Write a 1-wire data byte and return the sampled result. | |
| 150 */ | |
| 12 | 151 uint8_t |
| 0 | 152 OWTouchByte(uint8_t data) { |
| 12 | 153 uint8_t i, result = 0; |
| 0 | 154 |
| 155 for (i = 0; i < 8; i++) { | |
| 156 result >>= 1; | |
| 157 | |
| 158 /* If sending a 1 then read a bit, otherwise write a 0 */ | |
| 159 if (data & 0x01) { | |
| 160 if (OWReadBit()) | |
| 161 result |= 0x80; | |
| 162 } else | |
| 163 OWWriteBit(0); | |
| 164 | |
| 165 data >>= 1; | |
| 166 } | |
| 167 | |
| 168 return(result); | |
| 169 } | |
| 170 | |
| 171 /*----------------------------------------------------------------------------- | |
| 172 * Write a block of bytes to the 1-wire bus and return the sampled result in | |
| 173 * the same buffer | |
| 174 */ | |
| 175 void | |
| 176 OWBlock(uint8_t *data, int len) { | |
| 177 int i; | |
| 178 | |
| 179 for (i = 0; i < len; i++) | |
| 180 data[i] = OWTouchByte(data[i]); | |
| 181 } | |
| 182 | |
| 183 | |
| 184 /*----------------------------------------------------------------------------- | |
| 185 * Send a 1 wire command to a device, or all if no ROM ID provided | |
| 186 */ | |
| 187 void | |
| 188 OWSendCmd(uint8_t *ROM, uint8_t cmd) { | |
| 12 | 189 uint8_t i; |
| 0 | 190 |
| 191 OWTouchReset(); | |
| 192 | |
| 193 if (ROM == NULL) | |
| 194 OWWriteByte(OW_SKIP_ROM_CMD); | |
| 195 else { | |
| 196 OWWriteByte(OW_MATCH_ROM_CMD); | |
| 197 for (i = 0; i < 8; i++) | |
| 198 OWWriteByte(ROM[i]); | |
| 199 } | |
| 200 OWWriteByte(cmd); | |
| 201 } | |
| 202 | |
| 203 /*----------------------------------------------------------------------------- | |
| 204 * Search algorithm from App note 187 (and 162) | |
| 205 * | |
| 10 | 206 * OWFirst/OWNext return.. |
| 207 * 1 when something is found, | |
| 208 * 0 no more modules | |
| 16 | 209 * -1 if no presence pulse, |
| 10 | 210 * -2 if bad CRC, |
| 211 * -3 if bad wiring. | |
| 0 | 212 */ |
| 12 | 213 uint8_t |
| 0 | 214 OWFirst(uint8_t *ROM, uint8_t do_reset, uint8_t alarm_only) { |
| 215 /* Reset state */ | |
| 216 OW_LastDiscrepancy = 0; | |
| 217 OW_LastDevice = 0; | |
| 218 OW_LastFamilyDiscrepancy = 0; | |
| 219 | |
| 220 /* Go looking */ | |
| 221 return (OWNext(ROM, do_reset, alarm_only)); | |
| 222 } | |
| 223 | |
| 224 /* Returns 1 when something is found, 0 if nothing left */ | |
| 12 | 225 uint8_t |
| 0 | 226 OWNext(uint8_t *ROM, uint8_t do_reset, uint8_t alarm_only) { |
| 227 uint8_t bit_test, search_direction, bit_number; | |
| 10 | 228 uint8_t last_zero, rom_byte_number, rom_byte_mask; |
| 0 | 229 uint8_t lastcrc8, crcaccum; |
| 12 | 230 int8_t next_result; |
| 0 | 231 |
| 232 /* Init for search */ | |
| 21 | 233 bit_number = 1; |
| 234 last_zero = 0; | |
| 235 rom_byte_number = 0; | |
| 236 rom_byte_mask = 1; | |
| 237 next_result = OW_NOMODULES; | |
| 238 lastcrc8 = 0; | |
| 239 crcaccum = 0; | |
| 0 | 240 |
| 21 | 241 /* if the last call was not the last one */ |
| 242 if (!OW_LastDevice) { | |
| 243 /* check if reset first is requested */ | |
| 244 if (do_reset) { | |
| 245 /* reset the 1-wire | |
| 246 * if there are no parts on 1-wire, return 0 */ | |
| 41 | 247 OWPUTSP(PSTR("Resetting\r\n")); |
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248 switch (OWTouchReset()) { |
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249 case 0: |
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250 break; |
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251 |
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252 case 1: |
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253 /* reset the search */ |
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254 OW_LastDiscrepancy = 0; |
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255 OW_LastFamilyDiscrepancy = 0; |
| 41 | 256 OWPUTSP(PSTR("No devices on bus\r\n")); |
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257 return OW_NOPRESENCE; |
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258 break; |
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259 |
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260 case 2: |
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261 /* reset the search */ |
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262 OW_LastDiscrepancy = 0; |
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263 OW_LastFamilyDiscrepancy = 0; |
| 41 | 264 OWPUTSP(PSTR("Bus appears to be being held low\r\n")); |
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265 return OW_BADWIRE; |
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266 break; |
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267 |
| 21 | 268 } |
| 269 } | |
| 0 | 270 |
| 21 | 271 /* If finding alarming devices issue a different command */ |
| 272 if (alarm_only) | |
| 273 OWWriteByte(OW_SEARCH_ALRM_CMD); /* issue the alarming search command */ | |
| 274 else | |
| 275 OWWriteByte(OW_SEARCH_ROM_CMD); /* issue the search command */ | |
| 0 | 276 |
| 21 | 277 /* pause before beginning the search */ |
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278 OWDELAY_I; |
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279 OWDELAY_I; |
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280 OWDELAY_I; |
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281 |
| 21 | 282 /* loop to do the search */ |
| 283 do { | |
| 284 /* read a bit and its compliment */ | |
| 285 bit_test = OWReadBit() << 1; | |
| 286 bit_test |= OWReadBit(); | |
| 0 | 287 |
| 41 | 288 OWPRINTFP(PSTR("bit_test = %d\r\n"), bit_test); |
| 0 | 289 |
| 21 | 290 /* check for no devices on 1-wire */ |
| 291 if (bit_test == 3) { | |
| 41 | 292 OWPRINTFP(PSTR("bit_test = %d\r\n"), bit_test); |
| 21 | 293 return(OW_BADWIRE); |
| 294 } | |
| 295 else { | |
| 296 /* all devices coupled have 0 or 1 */ | |
| 297 if (bit_test > 0) | |
| 298 search_direction = !(bit_test & 0x01); /* bit write value for search */ | |
| 299 else { | |
| 300 /* if this discrepancy is before the Last Discrepancy | |
| 301 * on a previous OWNext then pick the same as last time */ | |
| 302 if (bit_number < OW_LastDiscrepancy) | |
| 303 search_direction = ((ROM[rom_byte_number] & rom_byte_mask) > 0); | |
| 304 else | |
| 305 /* if equal to last pick 1, if not then pick 0 */ | |
| 306 search_direction = (bit_number == OW_LastDiscrepancy); | |
| 0 | 307 |
| 21 | 308 /* if 0 was picked then record its position in LastZero */ |
| 309 if (search_direction == 0) { | |
| 310 last_zero = bit_number; | |
| 0 | 311 |
| 21 | 312 /* check for Last discrepancy in family */ |
| 313 if (last_zero < 9) | |
| 314 OW_LastFamilyDiscrepancy = last_zero; | |
| 315 } | |
| 316 } | |
| 0 | 317 |
| 21 | 318 /* set or clear the bit in the ROM byte rom_byte_number |
| 319 * with mask rom_byte_mask */ | |
| 320 if (search_direction == 1) | |
| 321 ROM[rom_byte_number] |= rom_byte_mask; | |
| 322 else | |
| 323 ROM[rom_byte_number] &= ~rom_byte_mask; | |
| 0 | 324 |
| 21 | 325 /* serial number search direction write bit */ |
| 326 OWWriteBit(search_direction); | |
| 0 | 327 |
| 21 | 328 /* increment the byte counter bit_number |
| 329 * and shift the mask rom_byte_mask */ | |
| 330 bit_number++; | |
| 331 rom_byte_mask <<= 1; | |
| 0 | 332 |
| 21 | 333 /* if the mask is 0 then go to new ROM byte rom_byte_number |
| 334 * and reset mask */ | |
| 335 if (rom_byte_mask == 0) { | |
| 336 OWCRC(ROM[rom_byte_number], &crcaccum); /* accumulate the CRC */ | |
| 337 lastcrc8 = crcaccum; | |
| 0 | 338 |
| 21 | 339 rom_byte_number++; |
| 340 rom_byte_mask = 1; | |
| 341 } | |
| 342 } | |
| 343 } while (rom_byte_number < 8); /* loop until through all ROM bytes 0-7 */ | |
| 0 | 344 |
| 21 | 345 /* if the search was successful then */ |
| 346 if (!(bit_number < 65) || lastcrc8) { | |
| 347 if (lastcrc8) { | |
| 41 | 348 OWPRINTFP(PSTR("Bad CRC (%d)\r\n"), lastcrc8); |
| 21 | 349 next_result = OW_BADCRC; |
| 350 } else { | |
| 351 /* search successful so set LastDiscrepancy,LastDevice,next_result */ | |
| 352 OW_LastDiscrepancy = last_zero; | |
| 353 OW_LastDevice = (OW_LastDiscrepancy == 0); | |
| 41 | 354 OWPRINTFP(PSTR("Last device = %d\r\n"), OW_LastDevice); |
| 21 | 355 next_result = OW_FOUND; |
| 356 } | |
| 357 } | |
| 358 } | |
| 0 | 359 |
| 21 | 360 /* if no device found then reset counters so next 'next' will be |
| 361 * like a first */ | |
| 362 if (next_result != OW_FOUND || ROM[0] == 0) { | |
| 363 OW_LastDiscrepancy = 0; | |
| 364 OW_LastDevice = 0; | |
| 365 OW_LastFamilyDiscrepancy = 0; | |
| 366 } | |
| 0 | 367 |
| 21 | 368 if (next_result == OW_FOUND && ROM[0] == 0x00) |
| 369 next_result = OW_BADWIRE; | |
| 10 | 370 |
| 21 | 371 return next_result; |
| 0 | 372 |
| 373 } | |
| 374 | |
| 375 uint8_t PROGMEM dscrc_table[] = { | |
| 376 0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65, | |
| 377 157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220, | |
| 378 35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98, | |
| 379 190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255, | |
| 380 70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7, | |
| 381 219, 133,103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154, | |
| 382 101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36, | |
| 383 248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185, | |
| 384 140,210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113,147, 205, | |
| 385 17, 79, 173, 243, 112, 46, 204, 146, 211,141, 111, 49, 178, 236, 14, 80, | |
| 386 175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82,176, 238, | |
| 387 50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115, | |
| 388 202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139, | |
| 389 87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22, | |
| 390 233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168, | |
| 391 116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53 | |
| 392 }; | |
| 393 | |
|
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394 /*----------------------------------------------------------------------------- |
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395 * Update *crc based on the value of x |
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396 */ |
| 0 | 397 void |
| 398 OWCRC(uint8_t x, uint8_t *crc) { | |
| 399 *crc = pgm_read_byte(&dscrc_table[(*crc) ^ x]); | |
| 400 } | |
|
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401 |
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402 /*----------------------------------------------------------------------------- |
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403 * Program a DS2502's memory |
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404 * |
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405 * Arguments |
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406 * ROM - ROM ID (or NULL to send SKIP_ROM) |
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407 * start - Start address (bytes) |
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408 * len - Length of data to write |
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409 * data - Data to write |
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410 * exact - If true, only accept exact matches for programming, |
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411 * otherwise only ensure the bits we requested were |
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412 * programmed [to 0] |
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413 * status - If true program status rather than memory |
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414 * |
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415 * Returns.. |
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416 * 0 if all is OK |
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417 * 1 if the programming was unsuccessful |
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418 * 2 if the parameters were invalid |
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419 * 3 if the DS2502 didn't respond appropriately (also happens if the |
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420 * module doesn't exist) |
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421 */ |
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422 uint8_t |
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423 OWProgROM(uint8_t *ROM, uint8_t start, uint8_t len, uint8_t *data, uint8_t exact, uint8_t status) { |
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424 #if defined(OWSETVPPON) && defined(OWSETVPPOFF) |
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425 uint8_t crc, i, tmp; |
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426 |
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427 /* Stupid programmer detection */ |
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428 if (status) { |
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429 if (start + len > 3) |
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430 return(2); |
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431 } else { |
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432 if (start + len > 127) |
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433 return(2); |
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434 } |
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435 |
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436 if (len < 1) |
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437 return(2); |
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438 |
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439 OWDELAY_I; |
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440 if (OWTouchReset() != 0) { |
| 41 | 441 cons_putsP(PSTR("No presence pulse\r\n")); |
|
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442 return(3); |
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443 } |
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444 |
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445 crc = 0; |
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446 |
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447 /* Send the command */ |
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448 if (status) { |
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449 OWSendCmd(ROM, OW_WRITE_STATUS); |
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450 OWCRC(OW_WRITE_STATUS, &crc); |
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451 } else { |
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452 OWSendCmd(ROM, OW_WRITE_MEMORY); |
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453 OWCRC(OW_WRITE_MEMORY, &crc); |
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454 } |
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455 |
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456 /* And the start address |
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457 * (2 bytes even though one would do) |
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458 */ |
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459 OWWriteByte(start); |
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460 OWCRC(start, &crc); |
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461 |
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462 OWWriteByte(0x00); |
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463 OWCRC(0x00, &crc); |
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464 |
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465 for (i = 0; i < len; i++) { |
| 41 | 466 cons_putsP(PSTR("Programming ")); |
| 467 cons_puts_hex(data[i]); | |
| 468 cons_putsP(PSTR(" to ")); | |
| 469 cons_puts_hex(start + i); | |
| 470 cons_putsP(PSTR("\r\n")); | |
|
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471 |
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472 OWWriteByte(data[i]); |
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473 OWCRC(data[i], &crc); |
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474 |
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475 tmp = OWReadByte(); |
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476 |
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477 if (crc != tmp) { |
| 41 | 478 cons_putsP(PSTR("CRC mismatch ")); |
| 479 cons_puts_hex(crc); | |
| 480 cons_putsP(PSTR(" vs ")); | |
| 481 cons_puts_hex(tmp); | |
| 482 cons_putsP(PSTR("\r\n")); | |
|
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483 |
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484 OWTouchReset(); |
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485 return(3); |
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486 } |
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487 |
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488 OWSETVPPON(); |
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489 OWDELAY_H; |
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490 OWSETVPPOFF(); |
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491 |
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492 tmp = OWReadByte(); |
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493 |
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494 /* Check the bits we turned off are off */ |
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495 /* |
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496 for (i = 0; i < 8; i++) |
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497 if (!(data[i] & 1 << i) && (tmp & 1 << i)) |
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498 return(-3); |
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499 */ |
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500 if ((!data[i] & tmp) != 0) { |
| 41 | 501 cons_putsP(PSTR("Readback mismatch ")); |
| 502 cons_puts_hex(data[i]); | |
| 503 cons_putsP(PSTR(" vs ")); | |
| 504 cons_puts_hex(data[i]); | |
| 505 cons_putsP(PSTR("\r\n")); | |
|
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506 |
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507 OWTouchReset(); |
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508 return(3); |
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509 } |
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510 |
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511 /* The DS2502 loads it's CRC register with the address of the |
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512 * next byte */ |
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513 crc = 0; |
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514 OWCRC(start + i + 1, &crc); |
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515 } |
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516 |
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517 return(0); |
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518 #else |
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519 return(1); |
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520 #endif |
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521 } |
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522 |
| 41 | 523 /* |
| 524 * OWGetTemp | |
| 525 * | |
| 526 * Get the temperature from a 1wire bus module | |
| 527 * | |
| 528 * Returns temperature in hundredths of a degree or OW_TEMP_xxx on | |
| 529 * error. | |
| 530 */ | |
| 531 int16_t | |
| 532 OWGetTemp(uint8_t *ROM) { | |
| 533 int8_t i; | |
| 534 uint8_t crc, buf[9]; | |
| 535 int16_t temp; | |
| 536 int16_t tfrac; | |
| 537 | |
| 538 if (ROM[0] != OW_FAMILY_TEMP) | |
| 539 return OW_TEMP_WRONG_FAM; | |
| 540 | |
| 541 OWSendCmd(ROM, OW_CONVERTT_CMD); | |
| 542 | |
| 543 i = 0; | |
| 544 | |
| 545 /* Wait for the conversion */ | |
| 546 while (OWReadBit() == 0) | |
| 547 i = 1; | |
| 548 | |
| 549 /* Check that we talked to a module and it did something */ | |
| 550 if (i == 0) { | |
| 551 return OW_TEMP_NO_ROM; | |
| 552 } | |
| 553 | |
| 554 OWSendCmd(ROM, OW_RD_SCR_CMD); | |
| 555 crc = 0; | |
| 556 for (i = 0; i < 8; i++) { | |
| 557 buf[i] = OWReadByte(); | |
| 558 OWCRC(buf[i], &crc); | |
| 559 } | |
| 560 buf[i] = OWReadByte(); | |
| 561 if (crc != buf[8]) | |
| 562 return OW_TEMP_CRC_ERR; | |
| 563 temp = buf[0]; | |
| 564 if (buf[1] & 0x80) | |
| 565 temp -= 256; | |
| 566 | |
| 567 /* Chop off 0.5 degree bit */ | |
| 568 temp >>= 1; | |
| 569 | |
| 570 /* Calulate the fractional remainder */ | |
| 571 tfrac = buf[7] - buf[6]; | |
| 572 | |
| 573 /* Work in 100'th of degreess to save on floats */ | |
| 574 tfrac *= (int16_t)100; | |
| 575 | |
| 576 /* Divide by count */ | |
| 577 tfrac /= buf[7]; | |
| 578 | |
| 579 /* Subtract 0.25 deg from temp */ | |
| 580 tfrac += 75; | |
| 581 if (tfrac < 100) | |
| 582 temp--; | |
| 583 else | |
| 584 tfrac -= 100; | |
| 585 | |
| 586 i = temp; | |
| 587 temp *= 100; | |
| 588 temp += tfrac; | |
| 589 | |
| 590 return(temp); | |
| 591 } |