DS1820.cpp

00001 #include "DS1820.h"
00002 
00003     #define ONEWIRE_INPUT(pin)  pin->input()
00004     #define ONEWIRE_OUTPUT(pin) pin->output()
00005     #define ONEWIRE_INIT(pin)
00006 
00007 #ifdef TARGET_NORDIC
00008 //NORDIC targets (NRF) use software delays since their ticker uses a 32kHz clock
00009     static uint32_t loops_per_us = 0;
00010     
00011     #define INIT_DELAY      init_soft_delay()
00012     #define ONEWIRE_DELAY_US(value) for(int cnt = 0; cnt < (value * loops_per_us) >> 5; cnt++) {__NOP(); __NOP(); __NOP();}
00013     
00014 void init_soft_delay( void ) {
00015     if (loops_per_us == 0) {
00016         loops_per_us = 1;
00017         Timer timey; 
00018         timey.start();
00019         ONEWIRE_DELAY_US(320000);                     
00020         timey.stop();
00021         loops_per_us = (320000 + timey.read_us() / 2) / timey.read_us();  
00022     }
00023 }
00024 #else
00025     #define INIT_DELAY
00026     #define ONEWIRE_DELAY_US(value) wait_us(value)
00027 #endif
00028 
00029 LinkedList<node> DS1820::probes;
00030  
00031  
00032 DS1820::DS1820 (PinName data_pin, PinName power_pin, bool power_polarity) : _datapin(data_pin), _parasitepin(power_pin) {
00033     int byte_counter;
00034     _power_polarity = power_polarity;
00035 
00036     _power_mosfet = power_pin != NC;
00037     
00038     for(byte_counter=0;byte_counter<9;byte_counter++)
00039         RAM[byte_counter] = 0x00;
00040     
00041     ONEWIRE_INIT((&_datapin));
00042     INIT_DELAY;
00043     
00044     if (unassignedProbe(&_datapin, _ROM))
00045 //        error("No unassigned DS1820 found!\n");
00046 // else   {
00047     {        
00048         _datapin.input();
00049         probes.append(this);
00050         _parasite_power = !read_power_supply();
00051     }
00052 }
00053 
00054 DS1820::~DS1820 (void) {
00055     node *tmp;
00056     for(int i=1; i<=probes.length(); i++)
00057     {
00058         tmp = probes.pop(i);
00059         if (tmp->data == this)
00060             probes.remove(i);
00061     }
00062 }
00063 
00064  
00065 bool DS1820::onewire_reset(DigitalInOut *pin) {
00066 // This will return false if no devices are present on the data bus
00067     bool presence=false;
00068     ONEWIRE_OUTPUT(pin);
00069     pin->write(0);          // bring low for 500 us
00070     ONEWIRE_DELAY_US(500);
00071     ONEWIRE_INPUT(pin);       // let the data line float high
00072     ONEWIRE_DELAY_US(90);            // wait 90us
00073     if (pin->read()==0) // see if any devices are pulling the data line low
00074         presence=true;
00075     ONEWIRE_DELAY_US(410);
00076     return presence;
00077 }
00078  
00079 void DS1820::onewire_bit_out (DigitalInOut *pin, bool bit_data) {
00080     ONEWIRE_OUTPUT(pin);
00081     pin->write(0);
00082     ONEWIRE_DELAY_US(3);                 // DXP modified from 5
00083     if (bit_data) {
00084         pin->write(1); // bring data line high
00085         ONEWIRE_DELAY_US(55);
00086     } else {
00087         ONEWIRE_DELAY_US(55);            // keep data line low
00088         pin->write(1);
00089         ONEWIRE_DELAY_US(10);            // DXP added to allow bus to float high before next bit_out
00090     }
00091 }
00092  
00093 void DS1820::onewire_byte_out(char data) { // output data character (least sig bit first).
00094     int n;
00095     for (n=0; n<8; n++) {
00096         onewire_bit_out(&this->_datapin, data & 0x01);
00097         data = data >> 1; // now the next bit is in the least sig bit position.
00098     }
00099 }
00100  
00101 bool DS1820::onewire_bit_in(DigitalInOut *pin) {
00102     bool answer;
00103     ONEWIRE_OUTPUT(pin);
00104     pin->write(0);
00105     ONEWIRE_DELAY_US(3);                 // DXP modofied from 5
00106     ONEWIRE_INPUT(pin);
00107     ONEWIRE_DELAY_US(10);                // DXP modified from 5
00108     answer = pin->read();
00109     ONEWIRE_DELAY_US(45);                // DXP modified from 50
00110     return answer;
00111 }
00112  
00113 char DS1820::onewire_byte_in() { // read byte, least sig byte first
00114     char answer = 0x00;
00115     int i;
00116     for (i=0; i<8; i++) {
00117         answer = answer >> 1; // shift over to make room for the next bit
00118         if (onewire_bit_in(&this->_datapin))
00119             answer = answer | 0x80; // if the data port is high, make this bit a 1
00120     }
00121     return answer;
00122 }
00123 
00124 bool DS1820::unassignedProbe(PinName pin) {
00125     DigitalInOut _pin(pin);
00126     ONEWIRE_INIT((&_pin));
00127     INIT_DELAY;
00128     char ROM_address[8];
00129     return search_ROM_routine(&_pin, 0xF0, ROM_address);
00130 }
00131  
00132 bool DS1820::unassignedProbe(DigitalInOut *pin, char *ROM_address) {
00133     return search_ROM_routine(pin, 0xF0, ROM_address);
00134 }
00135  
00136 bool DS1820::search_ROM_routine(DigitalInOut *pin, char command, char *ROM_address) {
00137     bool DS1820_done_flag = false;
00138     int DS1820_last_descrepancy = 0;
00139     char DS1820_search_ROM[8] = {0, 0, 0, 0, 0, 0, 0, 0};
00140     
00141     int descrepancy_marker, ROM_bit_index;
00142     bool return_value, Bit_A, Bit_B;
00143     char byte_counter, bit_mask;
00144  
00145     return_value=false;
00146     while (!DS1820_done_flag) {
00147         if (!onewire_reset(pin)) {
00148             return false;
00149         } else {
00150             ROM_bit_index=1;
00151             descrepancy_marker=0;
00152             char command_shift = command;
00153             for (int n=0; n<8; n++) {           // Search ROM command or Search Alarm command
00154                 onewire_bit_out(pin, command_shift & 0x01);
00155                 command_shift = command_shift >> 1; // now the next bit is in the least sig bit position.
00156             } 
00157             byte_counter = 0;
00158             bit_mask = 0x01;
00159             while (ROM_bit_index<=64) {
00160                 Bit_A = onewire_bit_in(pin);
00161                 Bit_B = onewire_bit_in(pin);
00162                 if (Bit_A & Bit_B) {
00163                     descrepancy_marker = 0; // data read error, this should never happen
00164                     ROM_bit_index = 0xFF;
00165                 } else {
00166                     if (Bit_A | Bit_B) {
00167                         // Set ROM bit to Bit_A
00168                         if (Bit_A) {
00169                             DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
00170                         } else {
00171                             DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
00172                         }
00173                     } else {
00174                         // both bits A and B are low, so there are two or more devices present
00175                         if ( ROM_bit_index == DS1820_last_descrepancy ) {
00176                             DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
00177                         } else {
00178                             if ( ROM_bit_index > DS1820_last_descrepancy ) {
00179                                 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
00180                                 descrepancy_marker = ROM_bit_index;
00181                             } else {
00182                                 if (( DS1820_search_ROM[byte_counter] & bit_mask) == 0x00 )
00183                                     descrepancy_marker = ROM_bit_index;
00184                             }
00185                         }
00186                     }
00187                     onewire_bit_out (pin, DS1820_search_ROM[byte_counter] & bit_mask);
00188                     ROM_bit_index++;
00189                     if (bit_mask & 0x80) {
00190                         byte_counter++;
00191                         bit_mask = 0x01;
00192                     } else {
00193                         bit_mask = bit_mask << 1;
00194                     }
00195                 }
00196             }
00197             DS1820_last_descrepancy = descrepancy_marker;
00198             if (ROM_bit_index != 0xFF) {
00199                 int i = 1;
00200                 node *list_container;
00201                 while(1) {
00202                     list_container = probes.pop(i);
00203                     if (list_container == NULL) {                             //End of list, or empty list
00204                         if (ROM_checksum_error(DS1820_search_ROM)) {          // Check the CRC
00205                             return false;
00206                         }
00207                         for(byte_counter=0;byte_counter<8;byte_counter++)
00208                             ROM_address[byte_counter] = DS1820_search_ROM[byte_counter];
00209                         return true;
00210                     } else {                    //Otherwise, check if ROM is already known
00211                         bool equal = true;
00212                         DS1820 *pointer = (DS1820*) list_container->data;
00213                         char *ROM_compare = pointer->_ROM;
00214                         
00215                         for(byte_counter=0;byte_counter<8;byte_counter++) {
00216                             if ( ROM_compare[byte_counter] != DS1820_search_ROM[byte_counter])
00217                                 equal = false;
00218                         }
00219                         if (equal)
00220                             break;
00221                         else
00222                             i++;
00223                     }
00224                 }                        
00225             }
00226         }
00227         if (DS1820_last_descrepancy == 0)
00228             DS1820_done_flag = true;
00229     }
00230     return return_value;
00231 }
00232  
00233 void DS1820::match_ROM() {
00234 // Used to select a specific device
00235     int i;
00236     onewire_reset(&this->_datapin);
00237     onewire_byte_out( 0x55);  //Match ROM command
00238     for (i=0;i<8;i++) {
00239         onewire_byte_out(_ROM[i]);
00240     }
00241 }
00242  
00243 void DS1820::skip_ROM() {
00244     onewire_reset(&this->_datapin);
00245     onewire_byte_out(0xCC);   // Skip ROM command
00246 }
00247  
00248 bool DS1820::ROM_checksum_error(char *_ROM_address) {
00249     char _CRC=0x00;
00250     int i;
00251     for(i=0;i<7;i++) // Only going to shift the lower 7 bytes
00252         _CRC = CRC_byte(_CRC, _ROM_address[i]);
00253     // After 7 bytes CRC should equal the 8th byte (ROM CRC)
00254     return (_CRC!=_ROM_address[7]); // will return true if there is a CRC checksum mis-match         
00255 }
00256  
00257 bool DS1820::RAM_checksum_error() {
00258     char _CRC=0x00;
00259     int i;
00260     for(i=0;i<8;i++) // Only going to shift the lower 8 bytes
00261         _CRC = CRC_byte(_CRC, RAM[i]);
00262     // After 8 bytes CRC should equal the 9th byte (RAM CRC)
00263     return (_CRC!=RAM[8]); // will return true if there is a CRC checksum mis-match        
00264 }
00265  
00266 char DS1820::CRC_byte (char _CRC, char byte ) {
00267     int j;
00268     for(j=0;j<8;j++) {
00269         if ((byte & 0x01 ) ^ (_CRC & 0x01)) {
00270             // DATA ^ LSB CRC = 1
00271             _CRC = _CRC>>1;
00272             // Set the MSB to 1
00273             _CRC = _CRC | 0x80;
00274             // Check bit 3
00275             if (_CRC & 0x04) {
00276                 _CRC = _CRC & 0xFB; // Bit 3 is set, so clear it
00277             } else {
00278                 _CRC = _CRC | 0x04; // Bit 3 is clear, so set it
00279             }
00280             // Check bit 4
00281             if (_CRC & 0x08) {
00282                 _CRC = _CRC & 0xF7; // Bit 4 is set, so clear it
00283             } else {
00284                 _CRC = _CRC | 0x08; // Bit 4 is clear, so set it
00285             }
00286         } else {
00287             // DATA ^ LSB CRC = 0
00288             _CRC = _CRC>>1;
00289             // clear MSB
00290             _CRC = _CRC & 0x7F;
00291             // No need to check bits, with DATA ^ LSB CRC = 0, they will remain unchanged
00292         }
00293         byte = byte>>1;
00294     }
00295 return _CRC;
00296 }
00297  
00298 int DS1820::convertTemperature(bool wait, devices device) {
00299     // Convert temperature into scratchpad RAM for all devices at once
00300     int delay_time = 750; // Default delay time
00301     char resolution;
00302     if (device==all_devices)
00303         skip_ROM();          // Skip ROM command, will convert for ALL devices
00304     else {
00305         match_ROM();
00306         if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
00307             resolution = RAM[4] & 0x60;
00308             if (resolution == 0x00) // 9 bits
00309                 delay_time = 94;
00310             if (resolution == 0x20) // 10 bits
00311                 delay_time = 188;
00312             if (resolution == 0x40) // 11 bits. Note 12bits uses the 750ms default
00313                 delay_time = 375;
00314         }
00315     }
00316     
00317     onewire_byte_out( 0x44);  // perform temperature conversion
00318     if (_parasite_power) {
00319         if (_power_mosfet) {
00320             _parasitepin = _power_polarity;     // Parasite power strong pullup
00321             wait_ms(delay_time);
00322             _parasitepin = !_power_polarity;
00323             delay_time = 0;
00324         } else {
00325             _datapin.output();
00326             _datapin.write(1);
00327             wait_ms(delay_time);
00328             _datapin.input();
00329         }
00330     } else {
00331         if (wait) {
00332             wait_ms(delay_time);
00333             delay_time = 0;
00334         }
00335     }
00336     return delay_time;
00337 }
00338  
00339 void DS1820::read_RAM() {
00340     // This will copy the DS1820's 9 bytes of RAM data
00341     // into the objects RAM array. Functions that use
00342     // RAM values will automaticly call this procedure.
00343     int i;
00344     match_ROM();             // Select this device
00345     onewire_byte_out( 0xBE);   //Read Scratchpad command
00346     for(i=0;i<9;i++) {
00347         RAM[i] = onewire_byte_in();
00348     }
00349 //    if (!RAM_checksum_error())
00350 //       crcerr = 1;
00351 }
00352 
00353 bool DS1820::setResolution(unsigned int resolution) {
00354     bool answer = false;
00355     resolution = resolution - 9;
00356     if (resolution < 4) {
00357         resolution = resolution<<5; // align the bits
00358         RAM[4] = (RAM[4] & 0x60) | resolution; // mask out old data, insert new
00359         write_scratchpad ((RAM[2]<<8) + RAM[3]);
00360 //        store_scratchpad (DS1820::this_device); // Need to test if this is required
00361         answer = true;
00362     }
00363     return answer;
00364 }
00365  
00366 void DS1820::write_scratchpad(int data) {
00367     RAM[3] = data;
00368     RAM[2] = data>>8;
00369     match_ROM();
00370     onewire_byte_out(0x4E);   // Copy scratchpad into DS1820 ram memory
00371     onewire_byte_out(RAM[2]); // T(H)
00372     onewire_byte_out(RAM[3]); // T(L)
00373     if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
00374         onewire_byte_out(RAM[4]); // Configuration register
00375     }
00376 }
00377  
00378 float DS1820::temperature(char scale) {
00379 // The data specs state that count_per_degree should be 0x10 (16), I found my devices
00380 // to have a count_per_degree of 0x4B (75). With the standard resolution of 1/2 deg C
00381 // this allowed an expanded resolution of 1/150th of a deg C. I wouldn't rely on this
00382 // being super acurate, but it does allow for a smooth display in the 1/10ths of a
00383 // deg C or F scales.
00384     float answer, remaining_count, count_per_degree;
00385     int reading;
00386     read_RAM();
00387     if (RAM_checksum_error())
00388         // Indicate we got a CRC error
00389         answer = invalid_conversion;
00390     else {
00391         reading = (RAM[1] << 8) + RAM[0];
00392         if (reading & 0x8000) { // negative degrees C
00393             reading = 0-((reading ^ 0xffff) + 1); // 2's comp then convert to signed int
00394         }
00395         answer = reading +0.0; // convert to floating point
00396         if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
00397             answer = answer / 16.0f;
00398         }
00399         else {
00400             remaining_count = RAM[6];
00401             count_per_degree = RAM[7];
00402             answer = floor(answer/2.0f) - 0.25f + (count_per_degree - remaining_count) / count_per_degree;
00403         }
00404         if (scale=='F' or scale=='f')
00405             // Convert to deg F
00406             answer = answer * 9.0f / 5.0f + 32.0f;
00407     }
00408     return answer;
00409 }
00410  
00411 bool DS1820::read_power_supply(devices device) {
00412 // This will return true if the device (or all devices) are Vcc powered
00413 // This will return false if the device (or ANY device) is parasite powered
00414     if (device==all_devices)
00415         skip_ROM();          // Skip ROM command, will poll for any device using parasite power
00416     else
00417         match_ROM();
00418     onewire_byte_out(0xB4);   // Read power supply command
00419     return onewire_bit_in(&this->_datapin);
00420 }
00421 
00422