Rainer Raul / Mbed 2 deprecated OneWireDrv

Test 1-wire , working wtih parasite power and few sensors with mixed power supply.

Dependencies:   mbed

onewire.cpp@1:f8aa0ff8d04a, 2022-05-18 (annotated)

Committer:
rainerraul
Date:
Wed May 18 10:09:56 2022 +0000
Revision:
1:f8aa0ff8d04a
Parent:
0:1197076b78f4 
test

Who changed what in which revision?

UserRevisionLine numberNew contents of line
macraj 0:1197076b78f4 1 #include "mbed.h"
macraj 0:1197076b78f4 2 #include "onewire.h"
macraj 0:1197076b78f4 3 #include "crc8.h"
macraj 0:1197076b78f4 4
macraj 0:1197076b78f4 5
macraj 0:1197076b78f4 6
macraj 0:1197076b78f4 7 // DS18B20 converted to run on mbed
macraj 0:1197076b78f4 8
macraj 0:1197076b78f4 9
macraj 0:1197076b78f4 10
macraj 0:1197076b78f4 11
macraj 0:1197076b78f4 12
rainerraul 1:f8aa0ff8d04a 13 DigitalInOut ow_pin(PB_2);
macraj 0:1197076b78f4 14
macraj 0:1197076b78f4 15
macraj 0:1197076b78f4 16
macraj 0:1197076b78f4 17 BYTE ow_reset(void) { // reset. Should improve to act as a presence pulse
macraj 0:1197076b78f4 18 BYTE err;
macraj 0:1197076b78f4 19
macraj 0:1197076b78f4 20 ow_pin.output();
macraj 0:1197076b78f4 21 ow_pin = 0; // bring low for 500 us
macraj 0:1197076b78f4 22 wait_us(500);
macraj 0:1197076b78f4 23 ow_pin.input();
macraj 0:1197076b78f4 24 wait_us(60);
macraj 0:1197076b78f4 25 err = ow_pin;
macraj 0:1197076b78f4 26 wait_us(240);
macraj 0:1197076b78f4 27 if ( ow_pin == 0 ) { // short circuit
macraj 0:1197076b78f4 28 err = OW_SHORT_CIRCUIT;
macraj 0:1197076b78f4 29 #ifdef DEBUG
macraj 0:1197076b78f4 30 printf("Error. Short circut!!!\n");
macraj 0:1197076b78f4 31 #endif
macraj 0:1197076b78f4 32 }
macraj 0:1197076b78f4 33 return err;
macraj 0:1197076b78f4 34 }
macraj 0:1197076b78f4 35
macraj 0:1197076b78f4 36 BYTE ow_bit_io( BYTE b ) {
macraj 0:1197076b78f4 37
macraj 0:1197076b78f4 38 ow_pin.output(); // drive bus low
macraj 0:1197076b78f4 39 ow_pin = 0;
macraj 0:1197076b78f4 40 wait_us(1); // Recovery-Time wuffwuff was 1
macraj 0:1197076b78f4 41 //ow_pin.input();
macraj 0:1197076b78f4 42 if ( b ) ow_pin.input(); // if bit is 1 set bus high (by ext. pull-up)
macraj 0:1197076b78f4 43
macraj 0:1197076b78f4 44 // delay was 15uS-1 see comment above
macraj 0:1197076b78f4 45 wait_us(15-1);
macraj 0:1197076b78f4 46 // ???ow_pin.input();
macraj 0:1197076b78f4 47 if ( ow_pin == 0 ) b = 0; // sample at end of read-timeslot
macraj 0:1197076b78f4 48
macraj 0:1197076b78f4 49 wait_us(60-15);
macraj 0:1197076b78f4 50 ow_pin.input();
macraj 0:1197076b78f4 51
macraj 0:1197076b78f4 52 return b;
macraj 0:1197076b78f4 53 }
macraj 0:1197076b78f4 54
macraj 0:1197076b78f4 55 BYTE ow_byte_wr( uint8_t b ) {
macraj 0:1197076b78f4 56 uint8_t i = 8, j;
macraj 0:1197076b78f4 57
macraj 0:1197076b78f4 58 do {
macraj 0:1197076b78f4 59 j = ow_bit_io( b & 1 );
macraj 0:1197076b78f4 60 b >>= 1;
macraj 0:1197076b78f4 61 if ( j ) b |= 0x80;
macraj 0:1197076b78f4 62 } while ( --i );
macraj 0:1197076b78f4 63
macraj 0:1197076b78f4 64 return b;
macraj 0:1197076b78f4 65 }
macraj 0:1197076b78f4 66
macraj 0:1197076b78f4 67
macraj 0:1197076b78f4 68 uint8_t ow_byte_rd( void ) {
macraj 0:1197076b78f4 69 // read by sending 0xff (a dontcare?)
macraj 0:1197076b78f4 70 return ow_byte_wr( 0xFF );
macraj 0:1197076b78f4 71 }
macraj 0:1197076b78f4 72
macraj 0:1197076b78f4 73
macraj 0:1197076b78f4 74
macraj 0:1197076b78f4 75 BYTE ow_rom_search( BYTE diff, BYTE *id ) {
macraj 0:1197076b78f4 76 BYTE i, j, next_diff;
macraj 0:1197076b78f4 77 BYTE b;
macraj 0:1197076b78f4 78
macraj 0:1197076b78f4 79 if ( ow_reset() ) return OW_PRESENCE_ERR; // error, no device found
macraj 0:1197076b78f4 80
macraj 0:1197076b78f4 81 ow_byte_wr( OW_SEARCH_ROM ); // ROM search command
macraj 0:1197076b78f4 82 next_diff = OW_LAST_DEVICE; // unchanged on last device
macraj 0:1197076b78f4 83
macraj 0:1197076b78f4 84 i = OW_ROMCODE_SIZE * 8; // 8 bytes
macraj 0:1197076b78f4 85
macraj 0:1197076b78f4 86 do {
macraj 0:1197076b78f4 87 j = 8; // 8 bits
macraj 0:1197076b78f4 88 do {
macraj 0:1197076b78f4 89 b = ow_bit_io( 1 ); // read bit
macraj 0:1197076b78f4 90 if ( ow_bit_io( 1 ) ) { // read complement bit
macraj 0:1197076b78f4 91 if ( b ) // 11
macraj 0:1197076b78f4 92 return OW_DATA_ERR; // data error
macraj 0:1197076b78f4 93 } else {
macraj 0:1197076b78f4 94 if ( !b ) { // 00 = 2 devices
macraj 0:1197076b78f4 95 if ( diff > i || ((*id & 1) && diff != i) ) {
macraj 0:1197076b78f4 96 b = 1; // now 1
macraj 0:1197076b78f4 97 next_diff = i; // next pass 0
macraj 0:1197076b78f4 98 }
macraj 0:1197076b78f4 99 }
macraj 0:1197076b78f4 100 }
macraj 0:1197076b78f4 101 ow_bit_io( b ); // write bit
macraj 0:1197076b78f4 102 *id >>= 1;
macraj 0:1197076b78f4 103 if ( b ) *id |= 0x80; // store bit
macraj 0:1197076b78f4 104
macraj 0:1197076b78f4 105 i--;
macraj 0:1197076b78f4 106
macraj 0:1197076b78f4 107 } while ( --j );
macraj 0:1197076b78f4 108
macraj 0:1197076b78f4 109 id++; // next byte
macraj 0:1197076b78f4 110
macraj 0:1197076b78f4 111 } while ( i );
macraj 0:1197076b78f4 112
macraj 0:1197076b78f4 113 return next_diff; // to continue search
macraj 0:1197076b78f4 114 }
macraj 0:1197076b78f4 115
macraj 0:1197076b78f4 116 void ow_command( BYTE command, BYTE *id ) {
macraj 0:1197076b78f4 117 BYTE i;
macraj 0:1197076b78f4 118
macraj 0:1197076b78f4 119 ow_reset();
macraj 0:1197076b78f4 120
macraj 0:1197076b78f4 121 if ( id ) {
macraj 0:1197076b78f4 122 ow_byte_wr( OW_MATCH_ROM ); // to a single device
macraj 0:1197076b78f4 123 i = OW_ROMCODE_SIZE;
macraj 0:1197076b78f4 124 do {
macraj 0:1197076b78f4 125 ow_byte_wr( *id );
macraj 0:1197076b78f4 126 id++;
macraj 0:1197076b78f4 127 } while ( --i );
macraj 0:1197076b78f4 128 } else {
macraj 0:1197076b78f4 129 ow_byte_wr( OW_SKIP_ROM ); // to all devices
macraj 0:1197076b78f4 130 }
macraj 0:1197076b78f4 131
macraj 0:1197076b78f4 132 ow_byte_wr( command );
macraj 0:1197076b78f4 133 }
macraj 0:1197076b78f4 134
macraj 0:1197076b78f4 135 void ow_parasite_enable(void) {
macraj 0:1197076b78f4 136 ow_pin.output();
macraj 0:1197076b78f4 137 ow_pin = 1;
macraj 0:1197076b78f4 138 }
macraj 0:1197076b78f4 139
macraj 0:1197076b78f4 140 void ow_parasite_disable(void) {
macraj 0:1197076b78f4 141
macraj 0:1197076b78f4 142 ow_pin.input();
macraj 0:1197076b78f4 143 }
macraj 0:1197076b78f4 144
macraj 0:1197076b78f4 145
macraj 0:1197076b78f4 146 /* find DS18X20 Sensors on 1-Wire-Bus
macraj 0:1197076b78f4 147 input/ouput: diff is the result of the last rom-search
macraj 0:1197076b78f4 148 output: id is the rom-code of the sensor found */
macraj 0:1197076b78f4 149 void DS18X20_find_sensor(BYTE *diff, BYTE id[]) {
macraj 0:1197076b78f4 150 for (;;) {
macraj 0:1197076b78f4 151 *diff = ow_rom_search( *diff, &id[0] );
macraj 0:1197076b78f4 152 if ( *diff==OW_PRESENCE_ERR || *diff==OW_DATA_ERR ||
macraj 0:1197076b78f4 153 *diff == OW_LAST_DEVICE ) return;
macraj 0:1197076b78f4 154 if ( id[0] == DS18B20_ID || id[0] == DS18S20_ID ) return;
macraj 0:1197076b78f4 155 }
macraj 0:1197076b78f4 156 }
macraj 0:1197076b78f4 157
macraj 0:1197076b78f4 158 /* get power status of DS18x20
macraj 0:1197076b78f4 159 input : id = rom_code
macraj 0:1197076b78f4 160 returns: DS18X20_POWER_EXTERN or DS18X20_POWER_PARASITE
macraj 0:1197076b78f4 161 */
macraj 0:1197076b78f4 162 BYTE DS18X20_get_power_status(uint8_t id[]) {
macraj 0:1197076b78f4 163 uint8_t pstat;
macraj 0:1197076b78f4 164 ow_reset();
macraj 0:1197076b78f4 165 ow_command(DS18X20_READ_POWER_SUPPLY, id);
macraj 0:1197076b78f4 166 pstat=ow_bit_io(1); // pstat 0=is parasite/ !=0 ext. powered
macraj 0:1197076b78f4 167 ow_reset();
macraj 0:1197076b78f4 168 return (pstat) ? DS18X20_POWER_EXTERN:DS18X20_POWER_PARASITE;
macraj 0:1197076b78f4 169 }
macraj 0:1197076b78f4 170
macraj 0:1197076b78f4 171 void DS18X20_show_id_uart( BYTE *id, size_t n ) {
macraj 0:1197076b78f4 172 size_t i;
macraj 0:1197076b78f4 173 for ( i = 0; i < n; i++ ) {
macraj 0:1197076b78f4 174 if ( i == 0 ) printf( "FC: " );
macraj 0:1197076b78f4 175 else if ( i == n-1 ) printf( "CRC: " );
macraj 0:1197076b78f4 176 if ( i == 1 ) printf( " SN: " );
macraj 0:1197076b78f4 177 printf("%X ",id[i]);
macraj 0:1197076b78f4 178 if ( i == 0 ) {
macraj 0:1197076b78f4 179 if ( id[0] == DS18S20_ID ) printf("(18S)");
macraj 0:1197076b78f4 180 else if ( id[0] == DS18B20_ID ) printf("(18B)");
macraj 0:1197076b78f4 181 else printf("( ? )");
macraj 0:1197076b78f4 182 }
macraj 0:1197076b78f4 183 }
macraj 0:1197076b78f4 184 if ( crc8( id, OW_ROMCODE_SIZE) )
macraj 0:1197076b78f4 185 printf( " CRC FAIL\n " );
macraj 0:1197076b78f4 186 else
macraj 0:1197076b78f4 187 printf( " CRC O.K.\n" );
macraj 0:1197076b78f4 188 }
macraj 0:1197076b78f4 189
macraj 0:1197076b78f4 190 /* start measurement (CONVERT_T) for all sensors if input id==NULL
macraj 0:1197076b78f4 191 or for single sensor. then id is the rom-code */
macraj 0:1197076b78f4 192 uint8_t DS18X20_start_meas( uint8_t with_power_extern, uint8_t id[]) {
macraj 0:1197076b78f4 193 ow_reset(); //**
macraj 0:1197076b78f4 194 if ( ow_pin ) { // only send if bus is "idle" = high
macraj 0:1197076b78f4 195 ow_command( DS18X20_CONVERT_T, id );
macraj 0:1197076b78f4 196 if (with_power_extern != DS18X20_POWER_EXTERN)
macraj 0:1197076b78f4 197 ow_parasite_enable();
macraj 0:1197076b78f4 198 return DS18X20_OK;
macraj 0:1197076b78f4 199 } else {
macraj 0:1197076b78f4 200 #ifdef DEBUG
macraj 0:1197076b78f4 201 printf( "DS18X20_start_meas: Short Circuit !\n" );
macraj 0:1197076b78f4 202 #endif
macraj 0:1197076b78f4 203 return DS18X20_START_FAIL;
macraj 0:1197076b78f4 204 }
macraj 0:1197076b78f4 205 }
macraj 0:1197076b78f4 206
macraj 0:1197076b78f4 207 /* reads temperature (scratchpad) of sensor with rom-code id
macraj 0:1197076b78f4 208 output: subzero==1 if temp.<0, cel: full celsius, mcel: frac
macraj 0:1197076b78f4 209 in millicelsius*0.1
rainerraul 1:f8aa0ff8d04a 210 i.e.: subzero=1, cel=18, millicel=5000 = -18,5000�C */
macraj 0:1197076b78f4 211 uint8_t DS18X20_read_meas(uint8_t id[], uint8_t *subzero,
macraj 0:1197076b78f4 212 uint8_t *cel, uint8_t *cel_frac_bits) {
macraj 0:1197076b78f4 213 uint8_t i;
macraj 0:1197076b78f4 214 uint8_t sp[DS18X20_SP_SIZE];
macraj 0:1197076b78f4 215
macraj 0:1197076b78f4 216 ow_reset(); //**
macraj 0:1197076b78f4 217 ow_command(DS18X20_READ, id);
macraj 0:1197076b78f4 218 for ( i=0 ; i< DS18X20_SP_SIZE; i++ ) sp[i]=ow_byte_rd();
macraj 0:1197076b78f4 219 if ( crc8( &sp[0], DS18X20_SP_SIZE ) )
macraj 0:1197076b78f4 220 return DS18X20_ERROR_CRC;
macraj 0:1197076b78f4 221 DS18X20_meas_to_cel(id[0], sp, subzero, cel, cel_frac_bits);
macraj 0:1197076b78f4 222 return DS18X20_OK;
macraj 0:1197076b78f4 223 }
macraj 0:1197076b78f4 224
macraj 0:1197076b78f4 225 /*
macraj 0:1197076b78f4 226 convert raw value from DS18x20 to Celsius
macraj 0:1197076b78f4 227 input is:
macraj 0:1197076b78f4 228 - familycode fc (0x10/0x28 see header)
macraj 0:1197076b78f4 229 - scratchpad-buffer
macraj 0:1197076b78f4 230 output is:
macraj 0:1197076b78f4 231 - cel full celsius
macraj 0:1197076b78f4 232 - fractions of celsius in millicelsius*(10^-1)/625 (the 4 LS-Bits)
macraj 0:1197076b78f4 233 - subzero =0 positiv / 1 negativ
macraj 0:1197076b78f4 234 always returns DS18X20_OK
macraj 0:1197076b78f4 235 TODO invalid-values detection (but should be covered by CRC)
macraj 0:1197076b78f4 236 */
macraj 0:1197076b78f4 237 uint8_t DS18X20_meas_to_cel( uint8_t fc, uint8_t *sp,
macraj 0:1197076b78f4 238 uint8_t* subzero, uint8_t* cel, uint8_t* cel_frac_bits) {
macraj 0:1197076b78f4 239 uint16_t meas;
macraj 0:1197076b78f4 240 uint8_t i;
macraj 0:1197076b78f4 241
macraj 0:1197076b78f4 242 meas = sp[0]; // LSB
macraj 0:1197076b78f4 243 meas |= ((uint16_t)sp[1])<<8; // MSB
macraj 0:1197076b78f4 244 //meas = 0xff5e; meas = 0xfe6f;
macraj 0:1197076b78f4 245
macraj 0:1197076b78f4 246 // only work on 12bit-base
macraj 0:1197076b78f4 247 if ( fc == DS18S20_ID ) { // 9 -> 12 bit if 18S20
macraj 0:1197076b78f4 248 /* Extended measurements for DS18S20 contributed by Carsten Foss */
macraj 0:1197076b78f4 249 meas &= (uint16_t) 0xfffe; // Discard LSB , needed for later extended precicion calc
macraj 0:1197076b78f4 250 meas <<= 3; // Convert to 12-bit , now degrees are in 1/16 degrees units
macraj 0:1197076b78f4 251 meas += (16 - sp[6]) - 4; // Add the compensation , and remember to subtract 0.25 degree (4/16)
macraj 0:1197076b78f4 252 }
macraj 0:1197076b78f4 253
macraj 0:1197076b78f4 254 // check for negative
macraj 0:1197076b78f4 255 if ( meas & 0x8000 ) {
macraj 0:1197076b78f4 256 *subzero=1; // mark negative
macraj 0:1197076b78f4 257 meas ^= 0xffff; // convert to positive => (twos complement)++
macraj 0:1197076b78f4 258 meas++;
macraj 0:1197076b78f4 259 } else *subzero=0;
macraj 0:1197076b78f4 260
macraj 0:1197076b78f4 261 // clear undefined bits for B != 12bit
macraj 0:1197076b78f4 262 if ( fc == DS18B20_ID ) { // check resolution 18B20
macraj 0:1197076b78f4 263 i = sp[DS18B20_CONF_REG];
macraj 0:1197076b78f4 264 if ( (i & DS18B20_12_BIT) == DS18B20_12_BIT ) ;
macraj 0:1197076b78f4 265 else if ( (i & DS18B20_11_BIT) == DS18B20_11_BIT )
macraj 0:1197076b78f4 266 meas &= ~(DS18B20_11_BIT_UNDF);
macraj 0:1197076b78f4 267 else if ( (i & DS18B20_10_BIT) == DS18B20_10_BIT )
macraj 0:1197076b78f4 268 meas &= ~(DS18B20_10_BIT_UNDF);
macraj 0:1197076b78f4 269 else { // if ( (i & DS18B20_9_BIT) == DS18B20_9_BIT ) {
macraj 0:1197076b78f4 270 meas &= ~(DS18B20_9_BIT_UNDF);
macraj 0:1197076b78f4 271 }
macraj 0:1197076b78f4 272 }
macraj 0:1197076b78f4 273
macraj 0:1197076b78f4 274 *cel = (uint8_t)(meas >> 4);
macraj 0:1197076b78f4 275 *cel_frac_bits = (uint8_t)(meas & 0x000F);
macraj 0:1197076b78f4 276
macraj 0:1197076b78f4 277 return DS18X20_OK;
macraj 0:1197076b78f4 278 }
macraj 0:1197076b78f4 279
macraj 0:1197076b78f4 280 /* converts to decicelsius
macraj 0:1197076b78f4 281 input is ouput from meas_to_cel
macraj 0:1197076b78f4 282 returns absolute value of temperatur in decicelsius
rainerraul 1:f8aa0ff8d04a 283 i.e.: sz=0, c=28, frac=15 returns 289 (=28.9�C)
macraj 0:1197076b78f4 284 0 0 0
macraj 0:1197076b78f4 285 1 625 625 1
macraj 0:1197076b78f4 286 2 1250 250
macraj 0:1197076b78f4 287 3 1875 875 3
macraj 0:1197076b78f4 288 4 2500 500 4
macraj 0:1197076b78f4 289 5 3125 125
macraj 0:1197076b78f4 290 6 3750 750 6
macraj 0:1197076b78f4 291 7 4375 375
macraj 0:1197076b78f4 292 8 5000 0
macraj 0:1197076b78f4 293 9 5625 625 9
macraj 0:1197076b78f4 294 10 6250 250
macraj 0:1197076b78f4 295 11 6875 875 11
macraj 0:1197076b78f4 296 12 7500 500 12
macraj 0:1197076b78f4 297 13 8125 125
macraj 0:1197076b78f4 298 14 8750 750 14
macraj 0:1197076b78f4 299 15 9375 375 */
macraj 0:1197076b78f4 300 uint16_t DS18X20_temp_to_decicel(uint8_t subzero, uint8_t cel,
macraj 0:1197076b78f4 301 uint8_t cel_frac_bits) {
macraj 0:1197076b78f4 302 uint16_t h;
macraj 0:1197076b78f4 303 uint8_t i;
macraj 0:1197076b78f4 304 uint8_t need_rounding[] = { 1, 3, 4, 6, 9, 11, 12, 14 };
macraj 0:1197076b78f4 305
macraj 0:1197076b78f4 306 h = cel_frac_bits*DS18X20_FRACCONV/1000;
macraj 0:1197076b78f4 307 h += cel*10;
macraj 0:1197076b78f4 308 if (!subzero) {
macraj 0:1197076b78f4 309 for (i=0; i<sizeof(need_rounding); i++) {
macraj 0:1197076b78f4 310 if ( cel_frac_bits == need_rounding[i] ) {
macraj 0:1197076b78f4 311 h++;
macraj 0:1197076b78f4 312 break;
macraj 0:1197076b78f4 313 }
macraj 0:1197076b78f4 314 }
macraj 0:1197076b78f4 315 }
macraj 0:1197076b78f4 316 return h;
macraj 0:1197076b78f4 317 }
macraj 0:1197076b78f4 318
macraj 0:1197076b78f4 319 /* compare temperature values (full celsius only)
macraj 0:1197076b78f4 320 returns -1 if param-pair1 < param-pair2
macraj 0:1197076b78f4 321 0 if ==
macraj 0:1197076b78f4 322 1 if > */
macraj 0:1197076b78f4 323 int8_t DS18X20_temp_cmp(uint8_t subzero1, uint16_t cel1,
macraj 0:1197076b78f4 324 uint8_t subzero2, uint16_t cel2) {
macraj 0:1197076b78f4 325 int16_t t1 = (subzero1) ? (cel1*(-1)) : (cel1);
macraj 0:1197076b78f4 326 int16_t t2 = (subzero2) ? (cel2*(-1)) : (cel2);
macraj 0:1197076b78f4 327
macraj 0:1197076b78f4 328 if (t1<t2) return -1;
macraj 0:1197076b78f4 329 if (t1>t2) return 1;
macraj 0:1197076b78f4 330 return 0;
macraj 0:1197076b78f4 331 }
macraj 0:1197076b78f4 332
macraj 0:1197076b78f4 333 void OneWireOutByte(unsigned char d) { // output byte d (least sig bit first).
macraj 0:1197076b78f4 334 for (int n=8; n!=0; n--) {
macraj 0:1197076b78f4 335 if ((d & 0x01) == 1) { // test least sig bit
macraj 0:1197076b78f4 336 ow_pin.output();
macraj 0:1197076b78f4 337 ow_pin = 0;
macraj 0:1197076b78f4 338 wait_us(5);
macraj 0:1197076b78f4 339 ow_pin.input();
macraj 0:1197076b78f4 340 wait_us(80);
macraj 0:1197076b78f4 341 } else {
macraj 0:1197076b78f4 342 ow_pin.output();
macraj 0:1197076b78f4 343 ow_pin = 0;
macraj 0:1197076b78f4 344 wait_us(80);
macraj 0:1197076b78f4 345 ow_pin.input();
macraj 0:1197076b78f4 346 }
macraj 0:1197076b78f4 347
macraj 0:1197076b78f4 348 d=d>>1; // now the next bit is in the least sig bit position.
macraj 0:1197076b78f4 349 }
macraj 0:1197076b78f4 350
macraj 0:1197076b78f4 351 }
macraj 0:1197076b78f4 352
macraj 0:1197076b78f4 353 unsigned char OneWireInByte() { // read byte, least sig byte first
macraj 0:1197076b78f4 354 unsigned char d = 0, b;
macraj 0:1197076b78f4 355 for (int n=0; n<8; n++) {
macraj 0:1197076b78f4 356 ow_pin.output();
macraj 0:1197076b78f4 357 ow_pin = 0;
macraj 0:1197076b78f4 358 wait_us(5);
macraj 0:1197076b78f4 359 ow_pin.input();
macraj 0:1197076b78f4 360 wait_us(5);
macraj 0:1197076b78f4 361 b =ow_pin;
macraj 0:1197076b78f4 362 wait_us(50);
macraj 0:1197076b78f4 363 d = (d >> 1) | (b << 7); // shift d to right and insert b in most sig bit position
macraj 0:1197076b78f4 364 }
macraj 0:1197076b78f4 365 return d;
macraj 0:1197076b78f4 366 }
macraj 0:1197076b78f4 367