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