OneWire.h

00001 #ifndef OneWire_h
00002 #define OneWire_h
00003 
00004 #include <inttypes.h>
00005 #include <mbed.h>
00006 #include "SerialBase.h"
00007 
00008 #define MODE()      _gpio->mode(PullUp)
00009 #define INPUT()     _gpio->input()
00010 #define OUTPUT()    _gpio->output()
00011 #define READ()      _gpio->read()
00012 #define WRITE(x)    _gpio->write(x)
00013 
00014 #ifdef TARGET_NORDIC
00015 //NORDIC targets (NRF) use software delays since their ticker uses a 32kHz clock
00016     static uint32_t loops_per_us = 0;
00017 
00018     #define INIT_WAIT   init_soft_delay()
00019     #define WAIT_US(x)  for(int cnt = 0; cnt < (x * loops_per_us) >> 5; cnt++) {__NOP(); __NOP(); __NOP();}
00020 
00021 void init_soft_delay( void ) {
00022     if (loops_per_us == 0) {
00023         loops_per_us = 1;
00024         Timer timey;
00025         timey.start();
00026         ONEWIRE_DELAY_US(320000);
00027         timey.stop();
00028         loops_per_us = (320000 + timey.read_us() / 2) / timey.read_us();
00029     }
00030 }
00031 #else
00032     #define INIT_WAIT
00033     #define WAIT_US(x)  wait_us(x)
00034 #endif
00035 
00036 // You can exclude certain features from OneWire.  In theory, this
00037 // might save some space.  In practice, the compiler automatically
00038 // removes unused code (technically, the linker, using -fdata-sections
00039 // and -ffunction-sections when compiling, and Wl,--gc-sections
00040 // when linking), so most of these will not result in any code size
00041 // reduction.  Well, unless you try to use the missing features
00042 // and redesign your program to not need them!  ONEWIRE_CRC8_TABLE
00043 // is the exception, because it selects a fast but large algorithm
00044 // or a small but slow algorithm.
00045 
00046 // you can exclude onewire_search by defining that to 0
00047 #ifndef ONEWIRE_SEARCH
00048 #define ONEWIRE_SEARCH 1
00049 #endif
00050 
00051 // You can exclude CRC checks altogether by defining this to 0
00052 #ifndef ONEWIRE_CRC
00053 #define ONEWIRE_CRC 1
00054 #endif
00055 
00056 class UART :
00057     public  SerialBase,
00058     private NonCopyable<UART>
00059 {
00060     UART(const UART&);
00061 public:
00062     UART(PinName tx, PinName rx, int baud) : SerialBase(tx, rx, baud) {}
00063 
00064     using SerialBase::_base_getc;
00065     using SerialBase::_base_putc;
00066 };
00067 
00068 class OneWire
00069 {
00070     DigitalInOut*   _gpio;
00071     UART*           _uart;
00072 
00073     int _samplePoint_us;
00074     int _outToInTransition_us;
00075 
00076 #if ONEWIRE_SEARCH
00077     // global search state
00078     unsigned char ROM_NO[8];
00079     uint8_t LastDiscrepancy;
00080     uint8_t LastFamilyDiscrepancy;
00081     uint8_t LastDeviceFlag;
00082 #endif
00083 
00084 public:
00085 
00086     // Constructors
00087     OneWire(PinName gpioPin, int samplePoint_us = 13);          // GPIO
00088     OneWire(PinName txPin, PinName rxPin, int baud = 115200);   // UART
00089 
00090     // Destructor
00091     ~OneWire();
00092 
00093     // Perform a 1-Wire reset cycle. Returns 1 if a device responds
00094     // with a presence pulse.  Returns 0 if there is no device or the
00095     // bus is shorted or otherwise held low for more than 250uS
00096     uint8_t reset(void);
00097 
00098     // Issue a 1-Wire rom select command, you do the reset first.
00099     void select(const uint8_t rom[8]);
00100 
00101     // Issue a 1-Wire rom skip command, to address all on bus.
00102     void skip(void);
00103 
00104     // Write a byte. If 'power' is one then the wire is held high at
00105     // the end for parasitically powered devices. You are responsible
00106     // for eventually depowering it by calling depower() or doing
00107     // another read or write.
00108     void write_byte(uint8_t v, uint8_t power = 0);
00109 
00110     void write_bytes(const uint8_t *buf, uint16_t count, bool power = 0);
00111 
00112     // Read a byte.
00113     uint8_t read_byte(void);
00114 
00115     void read_bytes(uint8_t *buf, uint16_t count);
00116 
00117     // Write a bit. The bus is always left powered at the end, see
00118     // note in write() about that.
00119     void write_bit(uint8_t v);
00120 
00121     // Read a bit.
00122     uint8_t read_bit(void);
00123 
00124     // Stop forcing power onto the bus. You only need to do this if
00125     // you used the 'power' flag to write() or used a write_bit() call
00126     // and aren't about to do another read or write. You would rather
00127     // not leave this powered if you don't have to, just in case
00128     // someone shorts your bus.
00129     void depower(void);
00130 
00131 #if ONEWIRE_SEARCH
00132     // Clear the search state so that if will start from the beginning again.
00133     void reset_search();
00134 
00135     // Setup the search to find the device type 'family_code' on the next call
00136     // to search(*newAddr) if it is present.
00137     void target_search(uint8_t family_code);
00138 
00139     // Look for the next device. Returns 1 if a new address has been
00140     // returned. A zero might mean that the bus is shorted, there are
00141     // no devices, or you have already retrieved all of them.  It
00142     // might be a good idea to check the CRC to make sure you didn't
00143     // get garbage.  The order is deterministic. You will always get
00144     // the same devices in the same order.
00145     uint8_t search(uint8_t *newAddr);
00146 #endif
00147 
00148 #if ONEWIRE_CRC
00149     // Compute a Dallas Semiconductor 8 bit CRC, these are used in the
00150     // ROM and scratchpad registers.
00151     static uint8_t crc8(const uint8_t *addr, uint8_t len);
00152 
00153 #if ONEWIRE_CRC16
00154     // Compute the 1-Wire CRC16 and compare it against the received CRC.
00155     // Example usage (reading a DS2408):
00156     //    // Put everything in a buffer so we can compute the CRC easily.
00157     //    uint8_t buf[13];
00158     //    buf[0] = 0xF0;    // Read PIO Registers
00159     //    buf[1] = 0x88;    // LSB address
00160     //    buf[2] = 0x00;    // MSB address
00161     //    WriteBytes(net, buf, 3);    // Write 3 cmd bytes
00162     //    ReadBytes(net, buf+3, 10);  // Read 6 data bytes, 2 0xFF, 2 CRC16
00163     //    if (!CheckCRC16(buf, 11, &buf[11])) {
00164     //        // Handle error.
00165     //    }
00166     //
00167     // @param input - Array of bytes to checksum.
00168     // @param len - How many bytes to use.
00169     // @param inverted_crc - The two CRC16 bytes in the received data.
00170     //                       This should just point into the received data,
00171     //                       *not* at a 16-bit integer.
00172     // @param crc - The crc starting value (optional)
00173     // @return True, iff the CRC matches.
00174     static bool check_crc16(const uint8_t* input, uint16_t len, const uint8_t* inverted_crc, uint16_t crc = 0);
00175 
00176     // Compute a Dallas Semiconductor 16 bit CRC.  This is required to check
00177     // the integrity of data received from many 1-Wire devices.  Note that the
00178     // CRC computed here is *not* what you'll get from the 1-Wire network,
00179     // for two reasons:
00180     //   1) The CRC is transmitted bitwise inverted.
00181     //   2) Depending on the endian-ness of your processor, the binary
00182     //      representation of the two-byte return value may have a different
00183     //      byte order than the two bytes you get from 1-Wire.
00184     // @param input - Array of bytes to checksum.
00185     // @param len - How many bytes to use.
00186     // @param crc - The crc starting value (optional)
00187     // @return The CRC16, as defined by Dallas Semiconductor.
00188     static uint16_t crc16(const uint8_t* input, uint16_t len, uint16_t crc = 0);
00189 #endif
00190 #endif
00191 };
00192 
00193 #endif
00194 
00195