OneWire.h

00001 #ifndef OneWire_h
00002 #define OneWire_h
00003 
00004 #include <inttypes.h>
00005 #include <mbed.h>
00006 
00007 #if defined(TARGET_STM)
00008     #define MODE()      output(); \
00009                         mode(OpenDrain)
00010     #define OUTPUT()    // configured as output in the constructor and stays like that forever
00011 #if defined(TARGET_STM32L072xx)
00012     #define PORT        ((GPIO_TypeDef *)(GPIOA_BASE + 0x0400 * STM_PORT(gpio.pin)))
00013     #define PINMASK     (1 << STM_PIN(gpio.pin))
00014     #define INPUT()     (PORT->MODER &= ~(GPIO_MODER_MODE0_0 << (STM_PIN(gpio.pin) * 2)))                              
00015     #define READ()      ((PORT->IDR & gpio.mask) != 0)
00016     #define WRITE(x)    (x == 1 ? PORT->BSRR = PINMASK : PORT->BRR = PINMASK)
00017 #else
00018     #define INPUT()     (*gpio.reg_set = gpio.mask) // write 1 to open drain
00019     #define READ()      ((*gpio.reg_in & gpio.mask) != 0)
00020     #define WRITE(x)    write(x)
00021 #endif
00022 #else
00023     #define MODE()      mode(PullUp)
00024     #define INPUT()     input()
00025     #define OUTPUT()    output()
00026     #define READ()      read()
00027     #define WRITE(x)    write(x)
00028 #endif
00029 
00030 #ifdef TARGET_NORDIC
00031 //NORDIC targets (NRF) use software delays since their ticker uses a 32kHz clock
00032     static uint32_t loops_per_us = 0;
00033     
00034     #define INIT_WAIT   init_soft_delay()
00035     #define WAIT_US(x)  for(int cnt = 0; cnt < (x * loops_per_us) >> 5; cnt++) {__NOP(); __NOP(); __NOP();}
00036     
00037 void init_soft_delay( void ) {
00038     if (loops_per_us == 0) {
00039         loops_per_us = 1;
00040         Timer timey; 
00041         timey.start();
00042         ONEWIRE_DELAY_US(320000);                     
00043         timey.stop();
00044         loops_per_us = (320000 + timey.read_us() / 2) / timey.read_us();  
00045     }
00046 }
00047 #else
00048     #define INIT_WAIT
00049     #define WAIT_US(x)  wait_us(x)
00050 #endif
00051 
00052 // You can exclude certain features from OneWire.  In theory, this
00053 // might save some space.  In practice, the compiler automatically
00054 // removes unused code (technically, the linker, using -fdata-sections
00055 // and -ffunction-sections when compiling, and Wl,--gc-sections
00056 // when linking), so most of these will not result in any code size
00057 // reduction.  Well, unless you try to use the missing features
00058 // and redesign your program to not need them!  ONEWIRE_CRC8_TABLE
00059 // is the exception, because it selects a fast but large algorithm
00060 // or a small but slow algorithm.
00061 
00062 // you can exclude onewire_search by defining that to 0
00063 #ifndef ONEWIRE_SEARCH
00064 #define ONEWIRE_SEARCH 1
00065 #endif
00066 
00067 // You can exclude CRC checks altogether by defining this to 0
00068 #ifndef ONEWIRE_CRC
00069 #define ONEWIRE_CRC 1
00070 #endif
00071 
00072 class OneWire : public DigitalInOut
00073 {
00074     int _sample_point_us;
00075     int _out_to_in_transition_us;
00076 
00077 #if ONEWIRE_SEARCH
00078     // global search state
00079     unsigned char ROM_NO[8];
00080     uint8_t LastDiscrepancy;
00081     uint8_t LastFamilyDiscrepancy;
00082     uint8_t LastDeviceFlag;
00083 #endif
00084 
00085 public:
00086     OneWire(PinName pin, int sample_point_us = 13);
00087 
00088     // Perform a 1-Wire reset cycle. Returns 1 if a device responds
00089     // with a presence pulse.  Returns 0 if there is no device or the
00090     // bus is shorted or otherwise held low for more than 250uS
00091     uint8_t reset(void);
00092 
00093     // Issue a 1-Wire rom select command, you do the reset first.
00094     void select(const uint8_t rom[8]);
00095 
00096     // Issue a 1-Wire rom skip command, to address all on bus.
00097     void skip(void);
00098 
00099     // Write a byte. If 'power' is one then the wire is held high at
00100     // the end for parasitically powered devices. You are responsible
00101     // for eventually depowering it by calling depower() or doing
00102     // another read or write.
00103     void write_byte(uint8_t v, uint8_t power = 0);
00104 
00105     void write_bytes(const uint8_t *buf, uint16_t count, bool power = 0);
00106 
00107     // Read a byte.
00108     uint8_t read_byte(void);
00109 
00110     void read_bytes(uint8_t *buf, uint16_t count);
00111 
00112     // Write a bit. The bus is always left powered at the end, see
00113     // note in write() about that.
00114     void write_bit(uint8_t v);
00115 
00116     // Read a bit.
00117     uint8_t read_bit(void);
00118 
00119     // Stop forcing power onto the bus. You only need to do this if
00120     // you used the 'power' flag to write() or used a write_bit() call
00121     // and aren't about to do another read or write. You would rather
00122     // not leave this powered if you don't have to, just in case
00123     // someone shorts your bus.
00124     void depower(void);
00125 
00126 #if ONEWIRE_SEARCH
00127     // Clear the search state so that if will start from the beginning again.
00128     void reset_search();
00129 
00130     // Setup the search to find the device type 'family_code' on the next call
00131     // to search(*newAddr) if it is present.
00132     void target_search(uint8_t family_code);
00133 
00134     // Look for the next device. Returns 1 if a new address has been
00135     // returned. A zero might mean that the bus is shorted, there are
00136     // no devices, or you have already retrieved all of them.  It
00137     // might be a good idea to check the CRC to make sure you didn't
00138     // get garbage.  The order is deterministic. You will always get
00139     // the same devices in the same order.
00140     uint8_t search(uint8_t *newAddr);
00141 #endif
00142 
00143 #if ONEWIRE_CRC
00144     // Compute a Dallas Semiconductor 8 bit CRC, these are used in the
00145     // ROM and scratchpad registers.
00146     static uint8_t crc8(const uint8_t *addr, uint8_t len);
00147 
00148 #if ONEWIRE_CRC16
00149     // Compute the 1-Wire CRC16 and compare it against the received CRC.
00150     // Example usage (reading a DS2408):
00151     //    // Put everything in a buffer so we can compute the CRC easily.
00152     //    uint8_t buf[13];
00153     //    buf[0] = 0xF0;    // Read PIO Registers
00154     //    buf[1] = 0x88;    // LSB address
00155     //    buf[2] = 0x00;    // MSB address
00156     //    WriteBytes(net, buf, 3);    // Write 3 cmd bytes
00157     //    ReadBytes(net, buf+3, 10);  // Read 6 data bytes, 2 0xFF, 2 CRC16
00158     //    if (!CheckCRC16(buf, 11, &buf[11])) {
00159     //        // Handle error.
00160     //    }     
00161     //          
00162     // @param input - Array of bytes to checksum.
00163     // @param len - How many bytes to use.
00164     // @param inverted_crc - The two CRC16 bytes in the received data.
00165     //                       This should just point into the received data,
00166     //                       *not* at a 16-bit integer.
00167     // @param crc - The crc starting value (optional)
00168     // @return True, iff the CRC matches.
00169     static bool check_crc16(const uint8_t* input, uint16_t len, const uint8_t* inverted_crc, uint16_t crc = 0);
00170 
00171     // Compute a Dallas Semiconductor 16 bit CRC.  This is required to check
00172     // the integrity of data received from many 1-Wire devices.  Note that the
00173     // CRC computed here is *not* what you'll get from the 1-Wire network,
00174     // for two reasons:
00175     //   1) The CRC is transmitted bitwise inverted.
00176     //   2) Depending on the endian-ness of your processor, the binary
00177     //      representation of the two-byte return value may have a different
00178     //      byte order than the two bytes you get from 1-Wire.
00179     // @param input - Array of bytes to checksum.
00180     // @param len - How many bytes to use.
00181     // @param crc - The crc starting value (optional)
00182     // @return The CRC16, as defined by Dallas Semiconductor.
00183     static uint16_t crc16(const uint8_t* input, uint16_t len, uint16_t crc = 0);
00184 #endif
00185 #endif
00186 };
00187 
00188 #endif
00189 
00190