Revision 0:1197076b78f4, committed 2010-05-10

Comitter:

macraj

Date:

Mon May 10 08:14:32 2010 +0000

Commit message:

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/crc8.cpp	Mon May 10 08:14:32 2010 +0000
@@ -0,0 +1,39 @@
+#include <inttypes.h>
+
+#define CRC8INIT	0x00
+#define CRC8POLY	0x18              //0X18 = X^8+X^5+X^4+X^0
+
+uint8_t	crc8 ( uint8_t *data_in, uint16_t number_of_bytes_to_read )
+{
+	uint8_t	 crc;
+	uint16_t loop_count;
+	uint8_t  bit_counter;
+	uint8_t  data;
+	uint8_t  feedback_bit;
+	
+	crc = CRC8INIT;
+
+	for (loop_count = 0; loop_count != number_of_bytes_to_read; loop_count++)
+	{
+		data = data_in[loop_count];
+		
+		bit_counter = 8;
+		do {
+			feedback_bit = (crc ^ data) & 0x01;
+	
+			if ( feedback_bit == 0x01 ) {
+				crc = crc ^ CRC8POLY;
+			}
+			crc = (crc >> 1) & 0x7F;
+			if ( feedback_bit == 0x01 ) {
+				crc = crc | 0x80;
+			}
+		
+			data = data >> 1;
+			bit_counter--;
+		
+		} while (bit_counter > 0);
+	}
+	
+	return crc;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/crc8.h	Mon May 10 08:14:32 2010 +0000
@@ -0,0 +1,1 @@
+uint8_t	crc8 (uint8_t* data_in, uint16_t number_of_bytes_to_read);
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon May 10 08:14:32 2010 +0000
@@ -0,0 +1,131 @@
+#include "mbed.h"
+#include "onewire.h"
+
+
+
+BYTE gSensorIDs[MAXSENSORS][OW_ROMCODE_SIZE];
+
+Serial pc(USBTX, USBRX); // tx, rx
+
+BYTE search_sensors(void) {
+    BYTE i;
+    BYTE id[OW_ROMCODE_SIZE];
+    BYTE diff, nSensors;
+
+    printf( "Scanning Bus for DS18X20\n" );
+
+    nSensors = 0;
+
+    for ( diff = OW_SEARCH_FIRST;
+            diff != OW_LAST_DEVICE && nSensors < MAXSENSORS ; ) {
+        DS18X20_find_sensor( &diff, &id[0] );
+
+        if ( diff == OW_PRESENCE_ERR ) {
+            printf( "No Sensor found\n" );
+            break;
+        }
+
+        if ( diff == OW_DATA_ERR ) {
+            printf( "Bus Error\n" );
+            break;
+        }
+
+        for (i=0;i<OW_ROMCODE_SIZE;i++)
+            gSensorIDs[nSensors][i]=id[i];
+
+        nSensors++;
+    }
+
+    return nSensors;
+}
+
+void uart_put_temp(const uint8_t subzero, uint8_t cel, uint8_t cel_frac_bits) {
+//   uint8_t buffer[sizeof(int)*8+1];
+    uint16_t decicelsius;
+
+    float temperature;
+    pc.printf("[%s", (subzero)?"-":"+");
+//    pc.printf("%d.",cel);
+    //itoa((cel_frac_bits*DS18X20_FRACCONV),buffer,10);
+    //sprintf(buffer, "%d",(cel_frac_bits*DS18X20_FRACCONV));
+    //j=4-strlen(buffer);
+    //for (i=0;i<j;i++) pc.printf("0");
+    //pc.printf("%s °C [",buffer);
+//    pc.printf("  freak %d ::", (cel_frac_bits*DS18X20_FRACCONV));
+    // "rounding"
+    //pc.printf((subzero)?'-':'+');
+    decicelsius = DS18X20_temp_to_decicel(subzero, cel, cel_frac_bits);
+    temperature = decicelsius;
+    temperature = temperature/10;
+    pc.printf("%4.1f C]\n", temperature);
+
+    //pc.printf( "%d 0°C]\n",decicelsius);
+
+}
+
+
+
+
+int main(void) {
+
+    pc.printf("Qantum 1 wire interface test!\n");
+    uint8_t nSensors, i;
+    uint8_t subzero, cel, cel_frac_bits;
+
+    nSensors = search_sensors();
+
+    ow_command( DS18X20_CONVERT_T, 0);
+
+    pc.printf("Sensors found : %d\n", nSensors);
+    if (nSensors > 0) {
+        for (i=0; i<nSensors; i++) {
+            pc.printf("Sensor # %d is a ", i+1);
+            if ( gSensorIDs[i][0] == DS18S20_ID) {
+                pc.printf("DS18S20/DS1820 ");
+            } else pc.printf("DS18B20 ");
+            if ( DS18X20_get_power_status( &gSensorIDs[i][0] ) ==
+                    DS18X20_POWER_PARASITE )
+                pc.printf( "parasite" );
+            else pc.printf( "externally" );
+            pc.printf( " powered\n" );
+            DS18X20_show_id_uart( &gSensorIDs[i][0], OW_ROMCODE_SIZE );
+        }
+    }
+
+    pc.printf( "Convert_T and Read Sensor by Sensor (reverse order)\n" );
+    for ( i=nSensors; i>0; i-- ) {
+        if ( DS18X20_start_meas( DS18X20_POWER_PARASITE, &gSensorIDs[i-1][0] ) == DS18X20_OK ) {
+            wait_ms(DS18B20_TCONV_12BIT);
+            pc.printf("Sensor# %d = ", i);
+            if ( DS18X20_read_meas( &gSensorIDs[i-1][0], &subzero, &cel, &cel_frac_bits) == DS18X20_OK ) {
+                uart_put_temp(subzero, cel, cel_frac_bits);
+            } else pc.printf("CRC Error (lost connection?)\n");
+
+        } else pc.printf("Start meas. failed (short circuit?)\n");
+    }
+
+    while (1) {
+        for ( i=nSensors; i>0; i-- ) {
+            // if ( DS18X20_start_meas( DS18X20_POWER_PARASITE, &gSensorIDs[i-1][0] ) == DS18X20_OK ) {
+            pc.printf("Sensor# %d = ", i);
+            if ( DS18X20_read_meas( &gSensorIDs[i-1][0], &subzero, &cel, &cel_frac_bits) == DS18X20_OK ) {
+                uart_put_temp(subzero, cel, cel_frac_bits);
+            } else pc.printf("CRC Error (lost connection?)\n");
+           
+            //if ( DS18X20_start_meas( DS18X20_POWER_PARASITE, &gSensorIDs[i-1][0] ) == DS18X20_OK ) {
+            //} else pc.printf("Start meas. failed (short circuit?)\n");
+        }
+            ow_command( DS18X20_CONVERT_T, 0);
+            ow_parasite_enable();
+
+
+        //  ow_reset();
+        //   ow_command( DS18X20_CONVERT_T, 0);
+        //   ow_parasite_enable();
+        wait(10);
+        //   ow_parasite_disable();
+
+    }
+
+}
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Mon May 10 08:14:32 2010 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/49a220cc26e0

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/onewire.cpp	Mon May 10 08:14:32 2010 +0000
@@ -0,0 +1,367 @@
+#include "mbed.h"
+#include "onewire.h"
+#include "crc8.h"
+
+
+
+// DS18B20 converted to run on mbed
+
+
+
+
+
+DigitalInOut ow_pin(ONEWIRE_PIN);
+
+
+
+BYTE ow_reset(void) { // reset.  Should improve to act as a presence pulse
+    BYTE err;
+
+    ow_pin.output();
+    ow_pin = 0;     // bring low for 500 us
+    wait_us(500);
+    ow_pin.input();
+    wait_us(60);
+    err = ow_pin;
+    wait_us(240);
+    if ( ow_pin == 0 )    {    // short circuit
+        err = OW_SHORT_CIRCUIT;
+#ifdef DEBUG
+        printf("Error. Short circut!!!\n");
+#endif
+    }
+    return err;
+}
+
+BYTE ow_bit_io( BYTE b ) {
+
+    ow_pin.output(); // drive bus low
+    ow_pin = 0;
+    wait_us(1); // Recovery-Time wuffwuff was 1
+    //ow_pin.input();
+    if ( b ) ow_pin.input(); // if bit is 1 set bus high (by ext. pull-up)
+
+    //  delay was 15uS-1 see comment above
+    wait_us(15-1);
+    // ???ow_pin.input();
+    if ( ow_pin == 0 ) b = 0; // sample at end of read-timeslot
+
+    wait_us(60-15);
+    ow_pin.input();
+
+    return b;
+}
+
+BYTE ow_byte_wr( uint8_t b ) {
+    uint8_t i = 8, j;
+
+    do {
+        j = ow_bit_io( b & 1 );
+        b >>= 1;
+        if ( j ) b |= 0x80;
+    } while ( --i );
+
+    return b;
+}
+
+
+uint8_t ow_byte_rd( void ) {
+    // read by sending 0xff (a dontcare?)
+    return ow_byte_wr( 0xFF );
+}
+
+
+
+BYTE ow_rom_search( BYTE diff, BYTE *id ) {
+    BYTE i, j, next_diff;
+    BYTE b;
+
+    if ( ow_reset() ) return OW_PRESENCE_ERR;    // error, no device found
+
+    ow_byte_wr( OW_SEARCH_ROM );            // ROM search command
+    next_diff = OW_LAST_DEVICE;            // unchanged on last device
+
+    i = OW_ROMCODE_SIZE * 8;                    // 8 bytes
+
+    do {
+        j = 8;                                // 8 bits
+        do {
+            b = ow_bit_io( 1 );                // read bit
+            if ( ow_bit_io( 1 ) ) {            // read complement bit
+                if ( b )                    // 11
+                    return OW_DATA_ERR;        // data error
+            } else {
+                if ( !b ) {                    // 00 = 2 devices
+                    if ( diff > i || ((*id & 1) && diff != i) ) {
+                        b = 1;                // now 1
+                        next_diff = i;        // next pass 0
+                    }
+                }
+            }
+            ow_bit_io( b );                 // write bit
+            *id >>= 1;
+            if ( b ) *id |= 0x80;            // store bit
+
+            i--;
+
+        } while ( --j );
+
+        id++;                                // next byte
+
+    } while ( i );
+
+    return next_diff;                // to continue search
+}
+
+void ow_command( BYTE command, BYTE *id ) {
+    BYTE i;
+
+    ow_reset();
+
+    if ( id ) {
+        ow_byte_wr( OW_MATCH_ROM );            // to a single device
+        i = OW_ROMCODE_SIZE;
+        do {
+            ow_byte_wr( *id );
+            id++;
+        } while ( --i );
+    } else {
+        ow_byte_wr( OW_SKIP_ROM );            // to all devices
+    }
+
+    ow_byte_wr( command );
+}
+
+void ow_parasite_enable(void) {
+    ow_pin.output();
+    ow_pin = 1;
+}
+
+void ow_parasite_disable(void) {
+
+    ow_pin.input();
+}
+
+
+/* find DS18X20 Sensors on 1-Wire-Bus
+   input/ouput: diff is the result of the last rom-search
+   output: id is the rom-code of the sensor found */
+void DS18X20_find_sensor(BYTE *diff, BYTE id[]) {
+    for (;;) {
+        *diff = ow_rom_search( *diff, &id[0] );
+        if ( *diff==OW_PRESENCE_ERR || *diff==OW_DATA_ERR ||
+                *diff == OW_LAST_DEVICE ) return;
+        if ( id[0] == DS18B20_ID || id[0] == DS18S20_ID ) return;
+    }
+}
+
+/* get power status of DS18x20
+   input  : id = rom_code
+   returns: DS18X20_POWER_EXTERN or DS18X20_POWER_PARASITE
+*/
+BYTE DS18X20_get_power_status(uint8_t id[]) {
+    uint8_t pstat;
+    ow_reset();
+    ow_command(DS18X20_READ_POWER_SUPPLY, id);
+    pstat=ow_bit_io(1); // pstat 0=is parasite/ !=0 ext. powered
+    ow_reset();
+    return (pstat) ? DS18X20_POWER_EXTERN:DS18X20_POWER_PARASITE;
+}
+
+void DS18X20_show_id_uart( BYTE *id, size_t n ) {
+    size_t i;
+    for ( i = 0; i < n; i++ ) {
+        if ( i == 0 ) printf( "FC: " );
+        else if ( i == n-1 ) printf( "CRC: " );
+        if ( i == 1 ) printf( " SN: " );
+        printf("%X ",id[i]);
+        if ( i == 0 ) {
+            if ( id[0] == DS18S20_ID ) printf("(18S)");
+            else if ( id[0] == DS18B20_ID ) printf("(18B)");
+            else printf("( ? )");
+        }
+    }
+    if ( crc8( id, OW_ROMCODE_SIZE) )
+        printf( " CRC FAIL\n " );
+    else
+        printf( " CRC O.K.\n" );
+}
+
+/* start measurement (CONVERT_T) for all sensors if input id==NULL
+   or for single sensor. then id is the rom-code */
+uint8_t DS18X20_start_meas( uint8_t with_power_extern, uint8_t id[]) {
+    ow_reset(); //**
+    if ( ow_pin ) { // only send if bus is "idle" = high
+        ow_command( DS18X20_CONVERT_T, id );
+        if (with_power_extern != DS18X20_POWER_EXTERN)
+            ow_parasite_enable();
+        return DS18X20_OK;
+    } else {
+#ifdef DEBUG
+        printf( "DS18X20_start_meas: Short Circuit !\n" );
+#endif
+        return DS18X20_START_FAIL;
+    }
+}
+
+/* reads temperature (scratchpad) of sensor with rom-code id
+   output: subzero==1 if temp.<0, cel: full celsius, mcel: frac
+   in millicelsius*0.1
+   i.e.: subzero=1, cel=18, millicel=5000 = -18,5000°C */
+uint8_t DS18X20_read_meas(uint8_t id[], uint8_t *subzero,
+                          uint8_t *cel, uint8_t *cel_frac_bits) {
+    uint8_t i;
+    uint8_t sp[DS18X20_SP_SIZE];
+
+    ow_reset(); //**
+    ow_command(DS18X20_READ, id);
+    for ( i=0 ; i< DS18X20_SP_SIZE; i++ ) sp[i]=ow_byte_rd();
+    if ( crc8( &sp[0], DS18X20_SP_SIZE ) )
+        return DS18X20_ERROR_CRC;
+    DS18X20_meas_to_cel(id[0], sp, subzero, cel, cel_frac_bits);
+    return DS18X20_OK;
+}
+
+/*
+   convert raw value from DS18x20 to Celsius
+   input is:
+   - familycode fc (0x10/0x28 see header)
+   - scratchpad-buffer
+   output is:
+   - cel full celsius
+   - fractions of celsius in millicelsius*(10^-1)/625 (the 4 LS-Bits)
+   - subzero =0 positiv / 1 negativ
+   always returns  DS18X20_OK
+   TODO invalid-values detection (but should be covered by CRC)
+*/
+uint8_t DS18X20_meas_to_cel( uint8_t fc, uint8_t *sp,
+                             uint8_t* subzero, uint8_t* cel, uint8_t* cel_frac_bits) {
+    uint16_t meas;
+    uint8_t  i;
+
+    meas = sp[0];  // LSB
+    meas |= ((uint16_t)sp[1])<<8; // MSB
+    //meas = 0xff5e; meas = 0xfe6f;
+
+    //  only work on 12bit-base
+    if ( fc == DS18S20_ID ) { // 9 -> 12 bit if 18S20
+        /* Extended measurements for DS18S20 contributed by Carsten Foss */
+        meas &= (uint16_t) 0xfffe;    // Discard LSB , needed for later extended precicion calc
+        meas <<= 3;                    // Convert to 12-bit , now degrees are in 1/16 degrees units
+        meas += (16 - sp[6]) - 4;    // Add the compensation , and remember to subtract 0.25 degree (4/16)
+    }
+
+    // check for negative
+    if ( meas & 0x8000 )  {
+        *subzero=1;      // mark negative
+        meas ^= 0xffff;  // convert to positive => (twos complement)++
+        meas++;
+    } else *subzero=0;
+
+    // clear undefined bits for B != 12bit
+    if ( fc == DS18B20_ID ) { // check resolution 18B20
+        i = sp[DS18B20_CONF_REG];
+        if ( (i & DS18B20_12_BIT) == DS18B20_12_BIT ) ;
+        else if ( (i & DS18B20_11_BIT) == DS18B20_11_BIT )
+            meas &= ~(DS18B20_11_BIT_UNDF);
+        else if ( (i & DS18B20_10_BIT) == DS18B20_10_BIT )
+            meas &= ~(DS18B20_10_BIT_UNDF);
+        else { // if ( (i & DS18B20_9_BIT) == DS18B20_9_BIT ) {
+            meas &= ~(DS18B20_9_BIT_UNDF);
+        }
+    }
+
+    *cel  = (uint8_t)(meas >> 4);
+    *cel_frac_bits = (uint8_t)(meas & 0x000F);
+
+    return DS18X20_OK;
+}
+
+/* converts to decicelsius
+   input is ouput from meas_to_cel
+   returns absolute value of temperatur in decicelsius
+    i.e.: sz=0, c=28, frac=15 returns 289 (=28.9°C)
+0    0    0
+1    625    625    1
+2    1250    250
+3    1875    875    3
+4    2500    500    4
+5    3125    125
+6    3750    750    6
+7    4375    375
+8    5000    0
+9    5625    625    9
+10    6250    250
+11    6875    875    11
+12    7500    500    12
+13    8125    125
+14    8750    750    14
+15    9375    375    */
+uint16_t DS18X20_temp_to_decicel(uint8_t subzero, uint8_t cel,
+                                 uint8_t cel_frac_bits) {
+    uint16_t h;
+    uint8_t  i;
+    uint8_t need_rounding[] = { 1, 3, 4, 6, 9, 11, 12, 14 };
+
+    h = cel_frac_bits*DS18X20_FRACCONV/1000;
+    h += cel*10;
+    if (!subzero) {
+        for (i=0; i<sizeof(need_rounding); i++) {
+            if ( cel_frac_bits == need_rounding[i] ) {
+                h++;
+                break;
+            }
+        }
+    }
+    return h;
+}
+
+/* compare temperature values (full celsius only)
+   returns -1 if param-pair1 < param-pair2
+            0 if ==
+            1 if >    */
+int8_t DS18X20_temp_cmp(uint8_t subzero1, uint16_t cel1,
+                        uint8_t subzero2, uint16_t cel2) {
+    int16_t t1 = (subzero1) ? (cel1*(-1)) : (cel1);
+    int16_t t2 = (subzero2) ? (cel2*(-1)) : (cel2);
+
+    if (t1<t2) return -1;
+    if (t1>t2) return 1;
+    return 0;
+}
+
+void OneWireOutByte(unsigned char d) { // output byte d (least sig bit first).
+    for (int n=8; n!=0; n--) {
+        if ((d & 0x01) == 1) { // test least sig bit
+            ow_pin.output();
+            ow_pin = 0;
+            wait_us(5);
+            ow_pin.input();
+            wait_us(80);
+        } else {
+            ow_pin.output();
+            ow_pin = 0;
+            wait_us(80);
+            ow_pin.input();
+        }
+
+        d=d>>1; // now the next bit is in the least sig bit position.
+    }
+
+}
+
+unsigned char OneWireInByte() { // read byte, least sig byte first
+    unsigned char d = 0, b;
+    for (int n=0; n<8; n++) {
+        ow_pin.output();
+        ow_pin = 0;
+        wait_us(5);
+        ow_pin.input();
+        wait_us(5);
+        b =ow_pin;
+        wait_us(50);
+        d = (d >> 1) | (b << 7); // shift d to right and insert b in most sig bit position
+    }
+    return d;
+}
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/onewire.h	Mon May 10 08:14:32 2010 +0000
@@ -0,0 +1,101 @@
+typedef unsigned char BYTE;
+
+
+#define MAXSENSORS 8
+// rom-code size including CRC
+#define OW_ROMCODE_SIZE 8
+
+
+
+
+BYTE ow_reset(void);
+BYTE ow_rom_search( BYTE diff, BYTE *id );
+void ow_command( BYTE command, BYTE *id );
+//void DS18X20_find_sensor(BYTE *diff, BYTE id[]);
+BYTE DS18X20_get_power_status(uint8_t id[]);
+
+extern void DS18X20_show_id_uart( uint8_t *id, size_t n );
+extern void DS18X20_find_sensor(uint8_t *diff, uint8_t id[]);    
+extern uint8_t    DS18X20_get_power_status(uint8_t id[]);
+extern uint8_t DS18X20_start_meas( uint8_t with_external, uint8_t id[]);
+extern uint8_t DS18X20_read_meas(uint8_t id[], uint8_t *subzero, uint8_t *cel, uint8_t *cel_frac_bits);
+extern uint8_t DS18X20_read_meas_single(uint8_t familycode, uint8_t *subzero, uint8_t *cel, uint8_t *cel_frac_bits);
+extern uint8_t DS18X20_meas_to_cel( uint8_t fc, uint8_t *sp, uint8_t* subzero, uint8_t* cel, uint8_t* cel_frac_bits);
+extern uint16_t DS18X20_temp_to_decicel(uint8_t subzero, uint8_t cel, uint8_t cel_frac_bits);
+extern int8_t DS18X20_temp_cmp(uint8_t subzero1, uint16_t cel1, uint8_t subzero2, uint16_t cel2);
+
+
+extern void ow_parasite_enable(void);
+extern void ow_parasite_disable(void);
+
+#define DEBUG 1
+
+#define ONEWIRE_PIN  p12
+
+
+#define OW_MATCH_ROM    0x55
+#define OW_SKIP_ROM     0xCC
+#define OW_SEARCH_ROM    0xF0
+
+
+#define OW_SHORT_CIRCUIT  0xFF
+#define OW_SEARCH_FIRST    0xFF        // start new search
+#define OW_PRESENCE_ERR    0x01
+#define OW_DATA_ERR     0xFE
+#define OW_LAST_DEVICE    0x00        // last device found
+//            0x01 ... 0x40: continue searching
+
+// rom-code size including CRC
+#define OW_ROMCODE_SIZE 8
+
+
+#define DS18X20_POWER_PARASITE 0x00
+#define DS18X20_POWER_EXTERN   0x01
+
+/* DS18X20 specific values (see datasheet) */
+#define DS18S20_ID 0x10
+#define DS18B20_ID 0x28
+#define DS18X20_CONVERT_T    0x44
+#define DS18X20_READ        0xBE
+#define DS18X20_WRITE        0x4E
+#define DS18X20_EE_WRITE    0x48
+#define DS18X20_EE_RECALL    0xB8
+#define DS18X20_READ_POWER_SUPPLY 0xB4
+
+#define DS18X20_OK          0x00
+#define DS18X20_ERROR       0x01
+#define DS18X20_START_FAIL  0x02
+#define DS18X20_ERROR_CRC   0x03
+
+
+#define DS18B20_CONF_REG    4
+#define DS18B20_9_BIT       0
+#define DS18B20_10_BIT      (1<<5)
+#define DS18B20_11_BIT      (1<<6)
+#define DS18B20_12_BIT      ((1<<6)|(1<<5))
+
+// indefined bits in LSB if 18B20 != 12bit
+#define DS18B20_9_BIT_UNDF       ((1<<0)|(1<<1)|(1<<2))
+#define DS18B20_10_BIT_UNDF      ((1<<0)|(1<<1))
+#define DS18B20_11_BIT_UNDF      ((1<<0))
+#define DS18B20_12_BIT_UNDF      0
+
+// conversion times in ms
+#define DS18B20_TCONV_12BIT      750
+#define DS18B20_TCONV_11BIT      DS18B20_TCONV_12_BIT/2
+#define DS18B20_TCONV_10BIT      DS18B20_TCONV_12_BIT/4
+#define DS18B20_TCONV_9BIT       DS18B20_TCONV_12_BIT/8
+#define DS18S20_TCONV            DS18B20_TCONV_12_BIT
+
+// constant to convert the fraction bits to cel*(10^-4)
+#define DS18X20_FRACCONV         625
+
+#define DS18X20_SP_SIZE  9
+
+// DS18X20 EEPROM-Support
+#define DS18X20_WRITE_SCRATCHPAD  0x4E
+#define DS18X20_COPY_SCRATCHPAD   0x48
+#define DS18X20_RECALL_E2         0xB8
+#define DS18X20_COPYSP_DELAY      10 /* ms */
+#define DS18X20_TH_REG      2
+#define DS18X20_TL_REG      3