Diff: DS18X20.c

Revision:

0:1449f126b241

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DS18X20.c	Sun Mar 03 01:41:51 2013 +0000
@@ -0,0 +1,204 @@
+/**
+* @file DS18x20.c
+* @brief library of DS18X20 1-Wire digital thermometer (http://www.maxim-ic.com/datasheet/index.mvp/id/2812)
+* @author Maciej Rajtar (Published 10 May 2010 www.mbed.org)
+* @author Frederic BLANC
+*/
+#include "mbed.h"
+#include "onewire.h"
+#include "DS18X20.h"
+#include "crc8.h"
+/**
+*     @brief get power status of DS18x20
+*    @param  [in] uint8_t id[] = rom_code
+*    @return DS18X20_POWER_EXTERN or DS18X20_POWER_PARASITE
+*     @date 20/06/2011
+*/
+uint8_t 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;
+}
+
+
+
+/**
+*   @brief start measurement (CONVERT_T) for all sensors if input id==NULL
+   or for single sensor. then id is the rom-code
+*    @param  [in] uint8_t with_power_extern
+*    @param  [in] uint8_t id[] = rom_code
+*    @return DS18X20_OK or DS18X20_START_FAIL
+*     @date 20/06/2011
+*/
+uint8_t DS18X20_start_meas( uint8_t with_power_extern, uint8_t id[]) {
+    ow_reset(); //**
+    if ( ow_test_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;
+    }
+    return DS18X20_START_FAIL;
+
+}
+
+/**
+*   @brief 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&#65533;C
+*    @param  [in] id[] = rom_code
+*    @param  [out] subzero
+*    @param  [out] cel
+*    @param  [out] cel_frac_bits
+*    @return DS18X20_OK or DS18X20_ERROR_CRC
+*     @date 20/06/2011
+*/
+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 ) ){
+          if ((sp[DS18X20_SP_SIZE-1]==0xFF) && (sp[DS18X20_SP_SIZE-2]==0xFF))
+            return OW_ERROR;    // bus error
+        return DS18X20_ERROR_CRC;    // data error
+    }
+        
+    DS18X20_meas_to_cel(id[0], sp, subzero, cel, cel_frac_bits);
+    return DS18X20_OK;
+}
+
+/**
+*   @brief 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)
+*    @param  [in] fc
+*    @param  [in] sp
+*    @param  [out] subzero
+*    @param  [out] cel
+*    @param  [out] cel_frac_bits
+*    @return DS18X20_OK
+*     @date 20/06/2011
+*/
+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;
+}
+
+/**
+*   @brief converts to decicelsius
+   input is ouput from meas_to_cel
+    i.e.: sz=0, c=28, frac=15 returns 289 (=28.9&#65533;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
+*    @param  [in]  subzero
+*    @param  [in]  cel
+*    @param  [in]  cel_frac_bits
+*    @return absolute value of temperatur in decicelsius
+*     @date 20/06/2011
+*/
+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;
+}
+/**
+*   @brief  compare temperature values (full celsius only)
+*    @param  [in] subzero1
+*    @param  [in] cel1
+*    @param  [in] subzero2
+*    @param  [in] cel2
+*    @return -1 if param-pair1 < param-pair2
+            0 if ==
+            1 if >
+*     @date 20/06/2011
+*/
+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;
+}
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