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_ROM[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_ROM_setup();
00057  *     // Loop to find all devices on the data line
00058  *     while (probe[devices_found]->search_ROM() 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]->ROM[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 public:
00083     enum devices{
00084         this_device,     // command applies to only this device
00085         all_devices };   // command applies to all devices
00086 
00087     /** Create a probe object connected to the specified pins
00088      *
00089      * @param data_pin DigitalInOut pin for the data bus
00090      * @param power_pin DigitalOut pin to control the power MOSFET
00091      */
00092     DS1820(PinName data_pin, PinName power_pin); // Constructor with parasite power pin
00093 
00094     /** Create a probe object connected to the specified pin
00095      *  this is used when all probes are externally powered
00096      *
00097      * @param data_pin DigitalInOut pin for the data bus
00098      */
00099     DS1820(PinName data_pin);
00100 
00101     /** ROM is a copy of the internal DS1820's ROM
00102       * It's created during the search_ROM() or search_alarm() commands
00103       *
00104       * ROM[0] is the Dallas Family Code
00105       * ROM[1] thru ROM[6] is the 48-bit unique serial number
00106       * ROM[7] is the device xCRC
00107       */
00108     char ROM[8];
00109     #define FAMILY_CODE ROM[0]
00110     #define FAMILY_CODE_DS1820 0x10
00111     #define FAMILY_CODE_DS18S20 0x10
00112     #define FAMILY_CODE_DS18B20 0x28
00113     
00114     /** RAM is a copy of the internal DS1820's RAM
00115       * It's updated during the read_RAM() command
00116       * which is automaticaly called from any function
00117       * using the RAM values.
00118       */
00119     char RAM[9];
00120     
00121     /* This function copies the DS1820's RAM into the object's
00122      * RAM[].
00123      */
00124     void read_RAM();
00125 
00126     /** This routine initializes the global variables used in
00127       * the search_ROM() and search_alarm() funtions. It should
00128       * be called once before looping to find devices.
00129       */
00130     void search_ROM_setup();
00131 
00132     /** This routine will search for an unidentified device
00133       * on the bus. It uses the variables in search_ROM_setup
00134       * to remember the pervious ROM address found.
00135       * It will return FALSE if there were no new devices
00136       * discovered on the bus.
00137       */
00138     bool search_ROM();
00139 
00140     /** This routine will search for an unidentified device
00141       * which has the temperature alarm bit set. It uses the 
00142       * variables in search_ROM_setup to remember the pervious 
00143       * ROM address found. It will return FALSE if there were 
00144       * no new devices with alarms discovered on the bus.
00145       */
00146     bool search_alarm();
00147 
00148     /** This routine will read the ROM (Family code, serial number
00149       * and Checksum) from a dedicated device on the bus.
00150       *
00151       * NOTE: This command can only be used when there is only one 
00152       *       DS1820 on the bus. If this command is used when there 
00153       *       is more than one slave present on the bus, a data 
00154       *       collision will occur when all the DS1820s attempt to 
00155       *       respond at the same time.
00156       */
00157     void read_ROM();
00158 
00159     /** This routine will initiate the temperature conversion within
00160       * a DS1820. There is a built in 750ms delay to allow the 
00161       * conversion to complete.
00162       *
00163       * To update all probes on the bus, use a statement such as this:
00164       * probe[0]->convert_temperature(DS1820::all_devices);
00165       *
00166       * @param allows the fnction to apply to a specific device or
00167       * to all devices on the 1-Wire bus.
00168       */
00169     void convert_temperature(devices device=this_device);
00170 
00171     /** This function will return the probe temperature. This function
00172       * uses the count remainding values to interpolate the temperature
00173       * to about 1/150th of a degree. Whereas the probe is not spec to
00174       * that precision. It does seem to give a smooth reading to the
00175       * tenth of a degree.
00176       *
00177       * @param scale, may be either 'c' or 'f'
00178       * @returns temperature for that scale
00179       */
00180     float temperature(char scale='c');
00181     
00182     /** This function calculates the ROM checksum and compares it to the
00183       * xCRC value stored in ROM[7].
00184       *
00185       * @returns true if the checksum matches, otherwise false.
00186       */
00187     bool ROM_checksum_error();
00188 
00189     /** This function calculates the RAM checksum and compares it to the
00190       * xCRC value stored in RAM[8].
00191       *
00192       * @returns true if the checksum matches, otherwise false.
00193       */
00194     bool RAM_checksum_error();
00195 
00196     /** This function returns the values stored in the temperature
00197       * alarm registers. 
00198       *
00199       * @returns a 16 bit integer of TH (upper byte) and TL (lower byte).
00200       */
00201     bool set_configuration_bits(unsigned int resolution);
00202     
00203     /** This function sets the temperature resolution for the DS18B20
00204       * in the configuration register.
00205       *
00206       * @param a number between 9 and 12 to specify the resolution
00207       * @returns true if successful
00208       */
00209     int read_scratchpad();
00210     
00211     /** This function will store the passed data into the DS1820's RAM.
00212       * Note: It does NOT save the data to the EEPROM for retention
00213       * during cycling the power off and on.
00214       *
00215       * @param a 16 bit integer of TH (upper byte) and TL (lower byte).
00216       */
00217     void write_scratchpad(int data);
00218     
00219     /** This function will transfer the TH and TL registers from the
00220       * DS1820's RAM into the EEPROM.
00221       * Note: There is a built in 10ms delay to allow for the
00222       * completion of the EEPROM write cycle.
00223       *
00224       * @param allows the fnction to apply to a specific device or
00225       * to all devices on the 1-Wire bus.
00226       */
00227     void store_scratchpad(devices device=this_device);
00228 
00229     /** This function will copy the stored values from the EEPROM
00230       * into the DS1820's RAM locations for TH and TL.
00231       *
00232       * @param allows the function to apply to a specific device or
00233       * to all devices on the 1-Wire bus.
00234       */
00235     int recall_scratchpad(devices device=this_device);
00236 
00237     /** This function will return the type of power supply for
00238       * a specific device. It can also be used to query all devices
00239       * looking for any device that is parasite powered.
00240       *
00241       * @returns true if the device (or all devices) are Vcc powered,
00242       * returns false if the device (or ANY device) is parasite powered.
00243       */
00244     bool read_power_supply(devices device=this_device);
00245 private:
00246     bool _parasite_power;
00247     char CRC_byte (char xCRC, char byte );
00248     bool onewire_reset();
00249     void match_ROM();
00250     void skip_ROM();
00251     bool search_ROM_routine(char command);
00252     void onewire_bit_out (bool bit_data);
00253     void onewire_byte_out(char data);
00254     bool onewire_bit_in();
00255     char onewire_byte_in();
00256 
00257 protected:
00258     DigitalInOut _datapin;
00259     DigitalOut _parasitepin;
00260 };
00261 
00262 
00263 #endif