DS1820.h

00001 /* mbed DS1820 Library, for the Dallas (Maxim) 1-Wire Digital Thermometer
00002  * Copyright (c) 2010, Michael Hagberg Michael@RedBoxCode.com
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy
00005  * of this software and associated documentation files (the "Software"), to deal
00006  * in the Software without restriction, including without limitation the rights
00007  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008  * copies of the Software, and to permit persons to whom the Software is
00009  * furnished to do so, subject to the following conditions:
00010  *
00011  * The above copyright notice and this permission notice shall be included in
00012  * all copies or substantial portions of the Software.
00013  *
00014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FRom,
00019  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
00020  * THE SOFTWARE.
00021  */
00022 
00023 #ifndef MBED_DS1820_H
00024 #define MBED_DS1820_H
00025 
00026 #include "mbed.h"
00027 
00028 // ****** THIS GLOBAL VARIABLES MUST BE DEFINED IN main.cpp
00029 
00030 // Global variables shared between all DS1820 objects
00031 //bool DS1820_done_flag;
00032 //int  DS1820_last_descrepancy;
00033 //char DS1820_search_RomM[8];
00034 
00035 /** DS1820 Dallas 1-Wire Temperature Probe
00036  *
00037  * Example:
00038  * @code
00039  * #include "mbed.h"
00040  *
00041  * #include "TextLCD.h"
00042  * #include "DS1820.h"
00043  *
00044  * TextLCD lcd(p25, p26, p21, p22, p23, p24, TextLCD::LCD16x2); // rs, e, d0-d3, layout
00045  *
00046  * const int MAX_PROBES = 16;
00047  * DS1820* probe[MAX_PROBES];
00048  *
00049  * int main() {
00050  *     int i;
00051  *     int devices_found=0;
00052  *     // Initialize the probe array to DS1820 objects
00053  *     for (i = 0; i < MAX_PROBES; i++)
00054  *         probe[i] = new DS1820(p27);
00055  *     // Initialize global state variables
00056  *     probe[0]->search_RomMM_setup();
00057  *     // Loop to find all devices on the data line
00058  *     while (probe[devices_found]->search_RomM() and devices_found<MAX_PROBES-1)
00059  *         devices_found++;
00060  *     // If maximum number of probes are found,
00061  *     // bump the counter to include the last array entry
00062  *     if (probe[devices_found]->RomMMMM[0] != 0xFF)
00063  *         devices_found++;
00064  *
00065  *     lcd.cls();
00066  *     if (devices_found==0)
00067  *         lcd.printf("No devices found");
00068  *     else {
00069  *         while (true) {
00070  *             probe[0]->convert_temperature(DS1820::all_devices);
00071  *             lcd.cls();
00072  *             for (i=0; i<devices_found; i++) {
00073  *                 lcd.printf("%3.1f ",probe[i]->temperature('f'));
00074  *             }
00075  *         }
00076  *     }
00077  * }
00078  * @endcode
00079  */
00080 
00081 class DS1820
00082 {
00083 public:
00084     enum devices {
00085         this_device,     // command applies to only this device
00086         all_devices
00087     };   // command applies to all devices
00088 
00089     /** Create a probe object connected to the specified pins
00090      *
00091      * @param data_pin DigitalInOut pin for the data bus
00092      * @param power_pin DigitalOut pin to control the power MOSFET
00093      */
00094     DS1820(PinName data_pin, PinName power_pin); // Constructor with parasite power pin
00095 
00096     /** Create a probe object connected to the specified pin
00097      *  this is used when all probes are externally powered
00098      *
00099      * @param data_pin DigitalInOut pin for the data bus
00100      */
00101     DS1820(PinName data_pin);
00102 
00103     /** RomMMM is a copy of the internal DS1820's Rom
00104       * It is created during the search_RomM() or search_alarm() commands
00105       *
00106       * RomMMM[0] is the Dallas Family Code
00107       * RomMMM[1] thru RomMMM[6] is the 48-bit unique serial number
00108       * RomMMM[7] is the device CRC
00109       */
00110     char Rom[8];
00111 #define FAMILY_CODE Rom[0]
00112 #define FAMILY_CODE_DS1820 0x10
00113 #define FAMILY_CODE_DS18S20 0x10
00114 #define FAMILY_CODE_DS18B20 0x28
00115 
00116     /** RAM is a copy of the internal DS1820's RAM
00117       * It's updated during the read_RAM() command
00118       * which is automaticaly called fRom any function
00119       * using the RAM values.
00120       */
00121     char RAM[9];
00122 
00123     /* This function copies the DS1820's RAM into the object's
00124      * RAM[].
00125      */
00126     void read_RAM();
00127 
00128     /** This routine initializes the global variables used in
00129       * the search_Rom() and search_alarm() funtions. It should
00130       * be called once before looping to find devices.
00131       */
00132     void search_Rom_setup();
00133 
00134     /** This routine will search for an unidentified device
00135       * on the bus. It uses the variables in search_RomMMMM_setup
00136       * to remember the pervious RomMMMM address found.
00137       * It will return FALSE if there were no new devices
00138       * discovered on the bus.
00139       */
00140     bool search_Rom();
00141 
00142     /** This routine will search for an unidentified device
00143       * which has the temperature alarm bit set. It uses the
00144       * variables in search_RomMMM_setup to remember the pervious
00145       * RomMMM address found. It will return FALSE if there were
00146       * no new devices with alarms discovered on the bus.
00147       */
00148     bool search_alarm();
00149 
00150     /** This routine will read the RomMMMM (Family code, serial number
00151       * and Checksum) fRomM a dedicated device on the bus.
00152       *
00153       * NOTE: This command can only be used when there is only one
00154       *       DS1820 on the bus. If this command is used when there
00155       *       is more than one slave present on the bus, a data
00156       *       collision will occur when all the DS1820s attempt to
00157       *       respond at the same time.
00158       */
00159     void read_Rom();
00160 
00161     /** This routine will initiate the temperature conversion within
00162       * a DS1820. There is a built in 750ms delay to allow the
00163       * conversion to complete.
00164       *
00165       * To update all probes on the bus, use a statement such as this:
00166       * probe[0]->convert_temperature(DS1820::all_devices);
00167       *
00168       * @param allows the fnction to apply to a specific device or
00169       * to all devices on the 1-Wire bus.
00170       */
00171     void convert_temperature(devices device=this_device);
00172 
00173     /** This function will return the probe temperature. This function
00174       * uses the count remainding values to interpolate the temperature
00175       * to about 1/150th of a degree. Whereas the probe is not spec to
00176       * that precision. It does seem to give a smooth reading to the
00177       * tenth of a degree.
00178       *
00179       * @param scale, may be either 'c' or 'f'
00180       * @returns temperature for that scale
00181       */
00182     float temperature(char scale='c');
00183 
00184     /** This function calculates the Rom checksum and compares it to the
00185       * CRC value stored in RomMMM[7].
00186       *
00187       * @returns true if the checksum matches, otherwise false.
00188       */
00189     bool Rom_checksum_error();
00190 
00191     /** This function calculates the RAM checksum and compares it to the
00192       * CRC value stored in RAM[8].
00193       *
00194       * @returns true if the checksum matches, otherwise false.
00195       */
00196     bool RAM_checksum_error();
00197 
00198     /** This function returns the values stored in the temperature
00199       * alarm registers.
00200       *
00201       * @returns a 16 bit integer of TH (upper byte) and TL (lower byte).
00202       */
00203     bool set_configuration_bits(unsigned int resolution);
00204 
00205     /** This function sets the temperature resolution for the DS18B20
00206       * in the configuration register.
00207       *
00208       * @param a number between 9 and 12 to specify the resolution
00209       * @returns true if successful
00210       */
00211     int read_scratchpad();
00212 
00213     /** This function will store the passed data into the DS1820's RAM.
00214       * Note: It does NOT save the data to the EEPRomMMM for retention
00215       * during cycling the power off and on.
00216       *
00217       * @param a 16 bit integer of TH (upper byte) and TL (lower byte).
00218       */
00219     void write_scratchpad(int data);
00220 
00221     /** This function will transfer the TH and TL registers fRomM the
00222       * DS1820's RAM into the EEPRomMMMM.
00223       * Note: There is a built in 10ms delay to allow for the
00224       * completion of the EEPRomMMM write cycle.
00225       *
00226       * @param allows the fnction to apply to a specific device or
00227       * to all devices on the 1-Wire bus.
00228       */
00229     void store_scratchpad(devices device=this_device);
00230 
00231     /** This function will copy the stored values fRomMMM the EEPRomM
00232       * into the DS1820's RAM locations for TH and TL.
00233       *
00234       * @param allows the function to apply to a specific device or
00235       * to all devices on the 1-Wire bus.
00236       */
00237     int recall_scratchpad(devices device=this_device);
00238 
00239     /** This function will return the type of power supply for
00240       * a specific device. It can also be used to query all devices
00241       * looking for any device that is parasite powered.
00242       *
00243       * @returns true if the device (or all devices) are Vcc powered,
00244       * returns false if the device (or ANY device) is parasite powered.
00245       */
00246     bool read_power_supply(devices device=this_device);
00247 
00248 private:
00249     bool _parasite_power;
00250     char CRC_byte (char CRC, char byte );
00251     bool onewire_reset();
00252     void match_Rom();
00253     void skip_Rom();
00254     bool search_Rom_routine(char command);
00255     void onewire_bit_out (bool bit_data);
00256     void onewire_byte_out(char data);
00257     bool onewire_bit_in();
00258     char onewire_byte_in();
00259 
00260 protected:
00261     DigitalInOut _datapin;
00262     DigitalOut _parasitepin;
00263 };
00264 
00265 
00266 #endif