Hugo Harming / Mbed 2 deprecated Lots_of_DS18B20

// Demo on how to identify and read multiple DS18B20 connected to the same bus. // Parasitic power is not used in this example. // This program is based on the sample code from Maxim/Dallas application // note 162 (http://www.maxim-ic.com/app-notes/index.mvp/id/162). Program output should look like this: *** Test with multiple DS18B20 *** Memory allocated for 20 devices. Scanning for devices... ROM CODE =62:00:00:01:CB:25:CA:28 1 ROM CODE =B6:00:00:01:CB:1B:9E:28 2 ROM CODE =66:00:00:01:CB:28:59:28 3 3 devices found. Scanning completed. Temp: 022.6875 Device: 000001CB25CA 001 Temp: 022.6875 Device: 000001CB1B9E 002 Temp: 027.6250 Device: 000001CB2859 003 Temp: 022.6250 Device: 000001CB25CA 001 Temp: 022.6875 Device: 000001CB1B9E 002 Temp: 025.3125 Device: 000001CB2859 003 Temp: 022.8125 Device: 000001CB25CA 001 Temp: 024.1875 Device: 000001CB1B9E 002 Temp: 023.7500 Device: 000001CB2859 003

Dependencies:   mbed

main.cpp@4:6ade7fcb2925, 2016-01-28 (annotated)

Committer:
RRacer
Date:
Thu Jan 28 09:05:50 2016 +0000
Revision:
4:6ade7fcb2925
Parent:
3:28b7b7fddede
Child:
7:cf5affdab535
Modified/added info text.; No program changes.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
RRacer 2:7ab1bf8540a3 1 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 2 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 3 // Lots_of_DS18B20
RRacer 2:7ab1bf8540a3 4 // Demo on how to identify and read multiple DS18B20 connected to the same bus.
RRacer 2:7ab1bf8540a3 5 // Parasitic power is not used in this example.
RRacer 2:7ab1bf8540a3 6 // This program is based on the sample code from Maxim/Dallas application
RRacer 2:7ab1bf8540a3 7 // note 162 (http://www.maxim-ic.com/app-notes/index.mvp/id/162).
RRacer 2:7ab1bf8540a3 8 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 9 //////////////////////////////////////////////////////////////////////////////
RRacer 4:6ade7fcb2925 10 // Program output should look like this:
RRacer 4:6ade7fcb2925 11 // *** Test with multiple DS18B20 ***
RRacer 4:6ade7fcb2925 12 // Memory allocated for 20 devices.
RRacer 4:6ade7fcb2925 13 // Scanning for devices...
RRacer 4:6ade7fcb2925 14 // ROM CODE =62:00:00:01:CB:25:CA:28 1
RRacer 4:6ade7fcb2925 15 // ROM CODE =B6:00:00:01:CB:1B:9E:28 2
RRacer 4:6ade7fcb2925 16 // ROM CODE =66:00:00:01:CB:28:59:28 3
RRacer 4:6ade7fcb2925 17 // 3 devices found. Scanning completed.
RRacer 4:6ade7fcb2925 18 // Temp: 022.6875 Device: 000001CB25CA 001
RRacer 4:6ade7fcb2925 19 // Temp: 022.6875 Device: 000001CB1B9E 002
RRacer 4:6ade7fcb2925 20 // Temp: 027.6250 Device: 000001CB2859 003
RRacer 4:6ade7fcb2925 21 // Temp: 022.6250 Device: 000001CB25CA 001
RRacer 4:6ade7fcb2925 22 // Temp: 022.6875 Device: 000001CB1B9E 002
RRacer 4:6ade7fcb2925 23 // Temp: 025.3125 Device: 000001CB2859 003
RRacer 4:6ade7fcb2925 24 // Temp: 022.8125 Device: 000001CB25CA 001
RRacer 4:6ade7fcb2925 25 // Temp: 024.1875 Device: 000001CB1B9E 002
RRacer 4:6ade7fcb2925 26 // Temp: 023.7500 Device: 000001CB2859 003
RRacer 4:6ade7fcb2925 27 //////////////////////////////////////////////////////////////////////////////
RRacer 4:6ade7fcb2925 28 //////////////////////////////////////////////////////////////////////////////
RRacer 4:6ade7fcb2925 29 // I have found that adding a small capacitor (100 nF or so) over the supply
RRacer 4:6ade7fcb2925 30 // lines on long cable runs significantly reduces the number of bad readings.
RRacer 4:6ade7fcb2925 31 // If you make temperature conversions more often than every 4-5 seconds, the
RRacer 4:6ade7fcb2925 32 // device(s) will self heat and produce a higher temperature reading.
RRacer 4:6ade7fcb2925 33 //////////////////////////////////////////////////////////////////////////////
RRacer 4:6ade7fcb2925 34 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 35
RRacer 2:7ab1bf8540a3 36 #include <mbed.h>
RRacer 2:7ab1bf8540a3 37 Serial pc(USBTX, USBRX);
RRacer 2:7ab1bf8540a3 38
RRacer 2:7ab1bf8540a3 39 #define FALSE 0
RRacer 2:7ab1bf8540a3 40 #define TRUE 1
RRacer 2:7ab1bf8540a3 41 #define MaxROMs 20 // Defines how many devices space is allocated for.
RRacer 2:7ab1bf8540a3 42
RRacer 4:6ade7fcb2925 43 DigitalInOut DQ(p30); // Attach the DQ pin of your sensors to this mbed pin.
RRacer 2:7ab1bf8540a3 44
RRacer 2:7ab1bf8540a3 45 unsigned char SPad[9]; // Scratchpad storage
RRacer 2:7ab1bf8540a3 46 unsigned char ROM[8];
RRacer 2:7ab1bf8540a3 47 unsigned char lastDiscrep = 0; // last discrepancy
RRacer 2:7ab1bf8540a3 48 unsigned char doneFlag = 0; // Done flag
RRacer 2:7ab1bf8540a3 49 unsigned char FoundROM[MaxROMs][8]; // table of found ROM codes
RRacer 2:7ab1bf8540a3 50 unsigned char numROMs; // Number of found devices.
RRacer 2:7ab1bf8540a3 51 unsigned char dowcrc;
RRacer 2:7ab1bf8540a3 52 unsigned char dscrc_table[] = {
RRacer 2:7ab1bf8540a3 53 0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
RRacer 2:7ab1bf8540a3 54 157,195, 33,127,252,162, 64, 30, 95, 1,227,189, 62, 96,130,220,
RRacer 2:7ab1bf8540a3 55 35,125,159,193, 66, 28,254,160,225,191, 93, 3,128,222, 60, 98,
RRacer 2:7ab1bf8540a3 56 190,224, 2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
RRacer 2:7ab1bf8540a3 57 70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89, 7,
RRacer 2:7ab1bf8540a3 58 219,133,103, 57,186,228, 6, 88, 25, 71,165,251,120, 38,196,154,
RRacer 2:7ab1bf8540a3 59 101, 59,217,135, 4, 90,184,230,167,249, 27, 69,198,152,122, 36,
RRacer 2:7ab1bf8540a3 60 248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91, 5,231,185,
RRacer 2:7ab1bf8540a3 61 140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
RRacer 2:7ab1bf8540a3 62 17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
RRacer 2:7ab1bf8540a3 63 175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
RRacer 2:7ab1bf8540a3 64 50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
RRacer 2:7ab1bf8540a3 65 202,148,118, 40,171,245, 23, 73, 8, 86,180,234,105, 55,213,139,
RRacer 2:7ab1bf8540a3 66 87, 9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
RRacer 2:7ab1bf8540a3 67 233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
RRacer 2:7ab1bf8540a3 68 116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};
RRacer 2:7ab1bf8540a3 69
RRacer 2:7ab1bf8540a3 70 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 71 // OW_RESET - performs a reset on the 1-wire bus and returns the presence detect.
RRacer 2:7ab1bf8540a3 72 unsigned char ow_reset(void) {
RRacer 2:7ab1bf8540a3 73 unsigned char presence;
RRacer 2:7ab1bf8540a3 74 DQ.output();
RRacer 2:7ab1bf8540a3 75 DQ = 0; //pull DQ line low
RRacer 2:7ab1bf8540a3 76 wait_us(480); // leave it low for 480us
RRacer 2:7ab1bf8540a3 77 DQ.input(); // allow line to return high
RRacer 2:7ab1bf8540a3 78 wait_us(70); // wait for presence
RRacer 2:7ab1bf8540a3 79 presence = DQ; // get presence signal
RRacer 2:7ab1bf8540a3 80 wait_us(410); // wait for end of timeslot
RRacer 4:6ade7fcb2925 81 return(presence); // presence signal returned, 0=presence, 1 = no sensor found.
RRacer 2:7ab1bf8540a3 82 }
RRacer 2:7ab1bf8540a3 83
RRacer 2:7ab1bf8540a3 84 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 85 // READ_BIT - reads a bit from the one-wire bus.
RRacer 2:7ab1bf8540a3 86 unsigned char read_bit(void) {
RRacer 2:7ab1bf8540a3 87 unsigned char retval;
RRacer 2:7ab1bf8540a3 88 wait_us(1); // Recovery time
RRacer 2:7ab1bf8540a3 89 DQ.output();
RRacer 2:7ab1bf8540a3 90 DQ = 0; // pull DQ low to start timeslot
RRacer 2:7ab1bf8540a3 91 wait_us(2);
RRacer 2:7ab1bf8540a3 92 DQ.input(); // Tristate line
RRacer 2:7ab1bf8540a3 93 wait_us(10); // delay 10 us from start of timeslot
RRacer 2:7ab1bf8540a3 94 retval=DQ;
RRacer 2:7ab1bf8540a3 95 wait_us(48); // minimum Read time slot: 60 us.
RRacer 2:7ab1bf8540a3 96 return(retval); // return value of DQ line
RRacer 2:7ab1bf8540a3 97 }
RRacer 2:7ab1bf8540a3 98
RRacer 2:7ab1bf8540a3 99 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 100 // WRITE_BIT - writes a bit to the one-wire bus, passed in bitval.
RRacer 2:7ab1bf8540a3 101 void write_bit(unsigned char bitval) {
RRacer 2:7ab1bf8540a3 102 wait_us(1); // Recovery time
RRacer 2:7ab1bf8540a3 103 DQ.output();
RRacer 2:7ab1bf8540a3 104 DQ = 0; // pull DQ low to start timeslot
RRacer 2:7ab1bf8540a3 105 wait_us(10);
RRacer 2:7ab1bf8540a3 106 if(bitval==1) DQ =1; // return DQ high if write 1
RRacer 2:7ab1bf8540a3 107 wait_us(50); // hold value for remainder of timeslot
RRacer 2:7ab1bf8540a3 108 DQ.input(); // Release line
RRacer 2:7ab1bf8540a3 109 }
RRacer 2:7ab1bf8540a3 110
RRacer 2:7ab1bf8540a3 111 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 112 // READ_BYTE - reads a byte from the one-wire bus.
RRacer 2:7ab1bf8540a3 113 unsigned char read_byte(void) {
RRacer 2:7ab1bf8540a3 114 unsigned char i, value=0;
RRacer 2:7ab1bf8540a3 115 for (i=0;i<8;i++) {
RRacer 2:7ab1bf8540a3 116 if(read_bit()) value|=0x01<<i; // reads byte in, one byte at a time and then shifts it left
RRacer 2:7ab1bf8540a3 117 }
RRacer 2:7ab1bf8540a3 118 return(value);
RRacer 2:7ab1bf8540a3 119 }
RRacer 2:7ab1bf8540a3 120
RRacer 2:7ab1bf8540a3 121 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 122 // WRITE_BYTE - writes a byte to the one-wire bus.
RRacer 2:7ab1bf8540a3 123 void write_byte(char val) {
RRacer 2:7ab1bf8540a3 124 unsigned char i;
RRacer 2:7ab1bf8540a3 125 unsigned char temp;
RRacer 2:7ab1bf8540a3 126 for (i=0; i<8; i++) {// writes byte, one bit at a time
RRacer 2:7ab1bf8540a3 127 temp = val>>i; // shifts val right 'i' spaces
RRacer 2:7ab1bf8540a3 128 temp &= 0x01; // copy that bit to temp
RRacer 4:6ade7fcb2925 129 write_bit(temp); // write bit
RRacer 2:7ab1bf8540a3 130 }
RRacer 2:7ab1bf8540a3 131 }
RRacer 2:7ab1bf8540a3 132
RRacer 2:7ab1bf8540a3 133 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 134 // ONE WIRE CRC
RRacer 2:7ab1bf8540a3 135 unsigned char ow_crc( unsigned char x) {
RRacer 2:7ab1bf8540a3 136 dowcrc = dscrc_table[dowcrc^x];
RRacer 2:7ab1bf8540a3 137 return dowcrc;
RRacer 2:7ab1bf8540a3 138 }
RRacer 2:7ab1bf8540a3 139
RRacer 2:7ab1bf8540a3 140 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 141 // NEXT
RRacer 2:7ab1bf8540a3 142 // The Next function searches for the next device on the 1-Wire bus. If
RRacer 2:7ab1bf8540a3 143 // there are no more devices on the 1-Wire then false is returned.
RRacer 2:7ab1bf8540a3 144 unsigned char Next(void) {
RRacer 2:7ab1bf8540a3 145 unsigned char m = 1; // ROM Bit index
RRacer 2:7ab1bf8540a3 146 unsigned char n = 0; // ROM Byte index
RRacer 2:7ab1bf8540a3 147 unsigned char k = 1; // bit mask
RRacer 2:7ab1bf8540a3 148 unsigned char x = 0;
RRacer 2:7ab1bf8540a3 149 unsigned char discrepMarker = 0; // discrepancy marker
RRacer 2:7ab1bf8540a3 150 unsigned char g; // Output bit
RRacer 2:7ab1bf8540a3 151 unsigned char nxt; // return value
RRacer 2:7ab1bf8540a3 152 int flag;
RRacer 4:6ade7fcb2925 153 nxt = FALSE; // set the nxt flag to false
RRacer 2:7ab1bf8540a3 154 dowcrc = 0; // reset the dowcrc
RRacer 2:7ab1bf8540a3 155 flag = ow_reset(); // reset the 1-Wire
RRacer 2:7ab1bf8540a3 156 if(flag||doneFlag) { // no parts -> return false
RRacer 2:7ab1bf8540a3 157 lastDiscrep = 0; // reset the search
RRacer 2:7ab1bf8540a3 158 return FALSE;
RRacer 2:7ab1bf8540a3 159 }
RRacer 2:7ab1bf8540a3 160 write_byte(0xF0); // send SearchROM command
RRacer 2:7ab1bf8540a3 161 do { // for all eight bytes
RRacer 2:7ab1bf8540a3 162 x = 0;
RRacer 2:7ab1bf8540a3 163 if(read_bit()==1) x = 2;
RRacer 2:7ab1bf8540a3 164 wait_us(120);
RRacer 2:7ab1bf8540a3 165 if(read_bit()==1) x |= 1; // and its complement
RRacer 2:7ab1bf8540a3 166 if(x ==3) // there are no devices on the 1-Wire
RRacer 2:7ab1bf8540a3 167 break;
RRacer 2:7ab1bf8540a3 168 else {
RRacer 2:7ab1bf8540a3 169 if(x>0) // all devices coupled have 0 or 1
RRacer 2:7ab1bf8540a3 170 g = x>>1; // bit write value for search
RRacer 2:7ab1bf8540a3 171 else {
RRacer 2:7ab1bf8540a3 172 // if this discrepancy is before the last discrepancy on a previous Next then pick the same as last time
RRacer 2:7ab1bf8540a3 173 if(m<lastDiscrep)
RRacer 2:7ab1bf8540a3 174 g = ((ROM[n]&k)>0);
RRacer 2:7ab1bf8540a3 175 else // if equal to last pick 1
RRacer 2:7ab1bf8540a3 176 g = (m==lastDiscrep); // if not then pick 0
RRacer 2:7ab1bf8540a3 177 // if 0 was picked then record position with mask k
RRacer 2:7ab1bf8540a3 178 if (g==0) discrepMarker = m;
RRacer 2:7ab1bf8540a3 179 }
RRacer 2:7ab1bf8540a3 180 if(g==1) // isolate bit in ROM[n] with mask k
RRacer 2:7ab1bf8540a3 181 ROM[n] |= k;
RRacer 2:7ab1bf8540a3 182 else
RRacer 2:7ab1bf8540a3 183 ROM[n] &= ~k;
RRacer 2:7ab1bf8540a3 184 write_bit(g); // ROM search write
RRacer 2:7ab1bf8540a3 185 m++; // increment bit counter m
RRacer 2:7ab1bf8540a3 186 k = k<<1; // and shift the bit mask k
RRacer 2:7ab1bf8540a3 187 if(k==0) { // if the mask is 0 then go to new ROM // byte n and reset mask
RRacer 2:7ab1bf8540a3 188 ow_crc(ROM[n]); // accumulate the CRC
RRacer 2:7ab1bf8540a3 189 n++; k++;
RRacer 2:7ab1bf8540a3 190 }
RRacer 2:7ab1bf8540a3 191 }
RRacer 2:7ab1bf8540a3 192 }
RRacer 2:7ab1bf8540a3 193 while(n<8); //loop until through all ROM bytes 0-7
RRacer 2:7ab1bf8540a3 194 if(m<65||dowcrc) // if search was unsuccessful then
RRacer 2:7ab1bf8540a3 195 lastDiscrep=0; // reset the last discrepancy to 0
RRacer 2:7ab1bf8540a3 196 else { // search was successful, so set lastDiscrep, lastOne, nxt
RRacer 2:7ab1bf8540a3 197 lastDiscrep = discrepMarker;
RRacer 2:7ab1bf8540a3 198 doneFlag = (lastDiscrep==0);
RRacer 2:7ab1bf8540a3 199 nxt = TRUE; // indicates search is not complete yet, more parts remain
RRacer 2:7ab1bf8540a3 200 }
RRacer 2:7ab1bf8540a3 201 return nxt;
RRacer 2:7ab1bf8540a3 202 }
RRacer 2:7ab1bf8540a3 203
RRacer 2:7ab1bf8540a3 204 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 205 // FIRST
RRacer 2:7ab1bf8540a3 206 // The First function resets the current state of a ROM search and calls
RRacer 2:7ab1bf8540a3 207 // Next to find the first device on the 1-Wire bus.
RRacer 2:7ab1bf8540a3 208 unsigned char First(void) {
RRacer 2:7ab1bf8540a3 209 lastDiscrep = 0; // reset the rom search last discrepancy global
RRacer 2:7ab1bf8540a3 210 doneFlag = FALSE;
RRacer 2:7ab1bf8540a3 211 return Next(); // call Next and return its return value
RRacer 2:7ab1bf8540a3 212 }
RRacer 2:7ab1bf8540a3 213
RRacer 2:7ab1bf8540a3 214 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 215 // FIND DEVICES
RRacer 2:7ab1bf8540a3 216 void FindDevices(void) {
RRacer 2:7ab1bf8540a3 217 unsigned char m;
RRacer 2:7ab1bf8540a3 218 if(!ow_reset()) { //Begins when a presence is detected
RRacer 2:7ab1bf8540a3 219 if(First()) { //Begins when at least one part is found
RRacer 2:7ab1bf8540a3 220 numROMs=0;
RRacer 2:7ab1bf8540a3 221 do {
RRacer 2:7ab1bf8540a3 222 numROMs++;
RRacer 2:7ab1bf8540a3 223 for(m=0;m<8;m++) {
RRacer 2:7ab1bf8540a3 224 FoundROM[numROMs][m]=ROM[m]; //Identifies ROM
RRacer 2:7ab1bf8540a3 225 }
RRacer 2:7ab1bf8540a3 226 pc.printf("ROM CODE =%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X %d\r\n",
RRacer 2:7ab1bf8540a3 227 FoundROM[numROMs][7],FoundROM[numROMs][6],FoundROM[numROMs][5],FoundROM[numROMs][4],
RRacer 2:7ab1bf8540a3 228 FoundROM[numROMs][3],FoundROM[numROMs][2],FoundROM[numROMs][1],FoundROM[numROMs][0],numROMs);
RRacer 2:7ab1bf8540a3 229 }
RRacer 2:7ab1bf8540a3 230 while (Next()&&(numROMs<MaxROMs)); //Continues until no additional devices are found
RRacer 2:7ab1bf8540a3 231 }
RRacer 2:7ab1bf8540a3 232 }
RRacer 2:7ab1bf8540a3 233 pc.printf("\n%d devices found.\r\n\n",numROMs);
RRacer 2:7ab1bf8540a3 234 }
RRacer 2:7ab1bf8540a3 235 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 236 void Read_ScratchPad(unsigned char n) { // Read the n first scratchpad bytes. Old data not wiped.
RRacer 2:7ab1bf8540a3 237 n=n % 10;
RRacer 2:7ab1bf8540a3 238 write_byte(0xBE);
RRacer 2:7ab1bf8540a3 239 for (int j=1;j<=n;j++){SPad[j-1]=read_byte();}
RRacer 2:7ab1bf8540a3 240 // CRC ********reserved******* Config Tl Th T MSB T LSB
RRacer 2:7ab1bf8540a3 241 pc.printf("\n ScratchPAD: %X%X%X%X%X%X%X%X%X\n",SPad[8],SPad[7],SPad[6],SPad[5],SPad[4],SPad[3],SPad[2],SPad[1],SPad[0]);
RRacer 2:7ab1bf8540a3 242 }
RRacer 2:7ab1bf8540a3 243
RRacer 2:7ab1bf8540a3 244 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 245 // Perform Match ROM
RRacer 2:7ab1bf8540a3 246 unsigned char Send_MatchRom(unsigned char DeviceNo) {
RRacer 2:7ab1bf8540a3 247 unsigned char i;
RRacer 2:7ab1bf8540a3 248 if(ow_reset()) return false;
RRacer 2:7ab1bf8540a3 249 write_byte(0x55); // match ROM
RRacer 2:7ab1bf8540a3 250 for(i=0;i<8;i++) {
RRacer 2:7ab1bf8540a3 251 write_byte(FoundROM[DeviceNo][i]); //send ROM code
RRacer 2:7ab1bf8540a3 252 }
RRacer 2:7ab1bf8540a3 253 return true;
RRacer 2:7ab1bf8540a3 254 }
RRacer 2:7ab1bf8540a3 255
RRacer 2:7ab1bf8540a3 256 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 257 void ConvT() { // Make all devices on the bus start a temperature conversion.
RRacer 2:7ab1bf8540a3 258 ow_reset();
RRacer 2:7ab1bf8540a3 259 write_byte( 0xcc); // Skip ROM command.
RRacer 2:7ab1bf8540a3 260 write_byte( 0x44); // Convert T command.
RRacer 2:7ab1bf8540a3 261 }
RRacer 2:7ab1bf8540a3 262
RRacer 2:7ab1bf8540a3 263 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 264 unsigned int ReadRawTemp(unsigned char device) {
RRacer 2:7ab1bf8540a3 265 int HighByte, LowByte;
RRacer 2:7ab1bf8540a3 266 Send_MatchRom(device); // Select device.
RRacer 2:7ab1bf8540a3 267 write_byte( 0xbe); // Read Scratchpad command.
RRacer 2:7ab1bf8540a3 268 LowByte=read_byte();
RRacer 2:7ab1bf8540a3 269 HighByte=read_byte();
RRacer 2:7ab1bf8540a3 270 return (HighByte << 8) + LowByte;
RRacer 2:7ab1bf8540a3 271 }
RRacer 2:7ab1bf8540a3 272
RRacer 2:7ab1bf8540a3 273 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 274 float Get_Temp(unsigned char device) {
RRacer 3:28b7b7fddede 275 int Raw = ReadRawTemp(device);
RRacer 3:28b7b7fddede 276 if((Raw>>8) & 0x80) { // Check if temperature is negative.
RRacer 3:28b7b7fddede 277 Raw = (Raw ^ 0xFFFF) + 1;
RRacer 3:28b7b7fddede 278 Raw *= -1;
RRacer 3:28b7b7fddede 279 }
RRacer 3:28b7b7fddede 280 float temperature = (float)Raw / 16.0;
RRacer 2:7ab1bf8540a3 281 return temperature;
RRacer 2:7ab1bf8540a3 282 }
RRacer 2:7ab1bf8540a3 283
RRacer 2:7ab1bf8540a3 284 //////////////////////////////////////////////////////////////////////////////
RRacer 2:7ab1bf8540a3 285 int main() {
RRacer 2:7ab1bf8540a3 286 float temperature;
RRacer 2:7ab1bf8540a3 287 DQ.output();
RRacer 2:7ab1bf8540a3 288 DQ = 0;
RRacer 2:7ab1bf8540a3 289 DQ.input();
RRacer 2:7ab1bf8540a3 290 pc.baud(9600);
RRacer 2:7ab1bf8540a3 291 pc.printf("\n\n*** Test with multiple DS18B20 ***\r\n\n");
RRacer 2:7ab1bf8540a3 292 pc.printf("Memory allocated for %d devices.\r\n",MaxROMs);
RRacer 2:7ab1bf8540a3 293 pc.printf("Scanning for devices...\r\n");
RRacer 2:7ab1bf8540a3 294 ow_reset();
RRacer 2:7ab1bf8540a3 295 FindDevices();
RRacer 2:7ab1bf8540a3 296 pc.printf("Scanning completed.\r\n");
RRacer 2:7ab1bf8540a3 297
RRacer 2:7ab1bf8540a3 298 while (1) {
RRacer 2:7ab1bf8540a3 299 ConvT(); // Issue Convert T command.
RRacer 2:7ab1bf8540a3 300 wait_ms(750); // Minimum 12-bit conversion time.
RRacer 2:7ab1bf8540a3 301 for(int i=1;i<=numROMs;i++) { // Cycle through found devices.
RRacer 2:7ab1bf8540a3 302 temperature = Get_Temp(i);
RRacer 2:7ab1bf8540a3 303 pc.printf("Temp: %08.4f Device: %02X%02X%02X%02X%02X%02X %03d\r\n",temperature,FoundROM[i][6],FoundROM[i][5],FoundROM[i][4],FoundROM[i][3],FoundROM[i][2],FoundROM[i][1],i);
RRacer 2:7ab1bf8540a3 304 }
RRacer 2:7ab1bf8540a3 305 pc.printf("\r\n");
RRacer 2:7ab1bf8540a3 306 wait(5); // Doing conversions more often will make devices self heat and produce a higher temperature reading.
RRacer 2:7ab1bf8540a3 307 }
RRacer 2:7ab1bf8540a3 308 }