Diff: OneWire.h

Revision:

0:acf75feb0947

Child:

6:28e60d774095

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/OneWire.h	Sun Mar 15 14:13:55 2015 +0000
@@ -0,0 +1,143 @@
+#ifndef OneWire_h
+#define OneWire_h
+
+#include <inttypes.h>
+#include <mbed.h>
+
+// You can exclude certain features from OneWire.  In theory, this
+// might save some space.  In practice, the compiler automatically
+// removes unused code (technically, the linker, using -fdata-sections
+// and -ffunction-sections when compiling, and Wl,--gc-sections
+// when linking), so most of these will not result in any code size
+// reduction.  Well, unless you try to use the missing features
+// and redesign your program to not need them!  ONEWIRE_CRC8_TABLE
+// is the exception, because it selects a fast but large algorithm
+// or a small but slow algorithm.
+
+// you can exclude onewire_search by defining that to 0
+#ifndef ONEWIRE_SEARCH
+#define ONEWIRE_SEARCH 1
+#endif
+
+// You can exclude CRC checks altogether by defining this to 0
+#ifndef ONEWIRE_CRC
+#define ONEWIRE_CRC 1
+#endif
+
+class OneWire
+{
+  private:
+    DigitalInOut    wire;
+
+#if ONEWIRE_SEARCH
+    // global search state
+    unsigned char ROM_NO[8];
+    uint8_t LastDiscrepancy;
+    uint8_t LastFamilyDiscrepancy;
+    uint8_t LastDeviceFlag;
+#endif
+
+  public:
+    OneWire(PinName pin);
+
+    // Perform a 1-Wire reset cycle. Returns 1 if a device responds
+    // with a presence pulse.  Returns 0 if there is no device or the
+    // bus is shorted or otherwise held low for more than 250uS
+    uint8_t reset(void);
+
+    // Issue a 1-Wire rom select command, you do the reset first.
+    void select(const uint8_t rom[8]);
+
+    // Issue a 1-Wire rom skip command, to address all on bus.
+    void skip(void);
+
+    // Write a byte. If 'power' is one then the wire is held high at
+    // the end for parasitically powered devices. You are responsible
+    // for eventually depowering it by calling depower() or doing
+    // another read or write.
+    void write(uint8_t v, uint8_t power = 0);
+
+    void write_bytes(const uint8_t *buf, uint16_t count, bool power = 0);
+
+    // Read a byte.
+    uint8_t read(void);
+
+    void read_bytes(uint8_t *buf, uint16_t count);
+
+    // Write a bit. The bus is always left powered at the end, see
+    // note in write() about that.
+    void write_bit(uint8_t v);
+
+    // Read a bit.
+    uint8_t read_bit(void);
+
+    // Stop forcing power onto the bus. You only need to do this if
+    // you used the 'power' flag to write() or used a write_bit() call
+    // and aren't about to do another read or write. You would rather
+    // not leave this powered if you don't have to, just in case
+    // someone shorts your bus.
+    void depower(void);
+
+#if ONEWIRE_SEARCH
+    // Clear the search state so that if will start from the beginning again.
+    void reset_search();
+
+    // Setup the search to find the device type 'family_code' on the next call
+    // to search(*newAddr) if it is present.
+    void target_search(uint8_t family_code);
+
+    // Look for the next device. Returns 1 if a new address has been
+    // returned. A zero might mean that the bus is shorted, there are
+    // no devices, or you have already retrieved all of them.  It
+    // might be a good idea to check the CRC to make sure you didn't
+    // get garbage.  The order is deterministic. You will always get
+    // the same devices in the same order.
+    uint8_t search(uint8_t *newAddr);
+#endif
+
+#if ONEWIRE_CRC
+    // Compute a Dallas Semiconductor 8 bit CRC, these are used in the
+    // ROM and scratchpad registers.
+    static uint8_t crc8(const uint8_t *addr, uint8_t len);
+
+#if ONEWIRE_CRC16
+    // Compute the 1-Wire CRC16 and compare it against the received CRC.
+    // Example usage (reading a DS2408):
+    //    // Put everything in a buffer so we can compute the CRC easily.
+    //    uint8_t buf[13];
+    //    buf[0] = 0xF0;    // Read PIO Registers
+    //    buf[1] = 0x88;    // LSB address
+    //    buf[2] = 0x00;    // MSB address
+    //    WriteBytes(net, buf, 3);    // Write 3 cmd bytes
+    //    ReadBytes(net, buf+3, 10);  // Read 6 data bytes, 2 0xFF, 2 CRC16
+    //    if (!CheckCRC16(buf, 11, &buf[11])) {
+    //        // Handle error.
+    //    }     
+    //          
+    // @param input - Array of bytes to checksum.
+    // @param len - How many bytes to use.
+    // @param inverted_crc - The two CRC16 bytes in the received data.
+    //                       This should just point into the received data,
+    //                       *not* at a 16-bit integer.
+    // @param crc - The crc starting value (optional)
+    // @return True, iff the CRC matches.
+    static bool check_crc16(const uint8_t* input, uint16_t len, const uint8_t* inverted_crc, uint16_t crc = 0);
+
+    // Compute a Dallas Semiconductor 16 bit CRC.  This is required to check
+    // the integrity of data received from many 1-Wire devices.  Note that the
+    // CRC computed here is *not* what you'll get from the 1-Wire network,
+    // for two reasons:
+    //   1) The CRC is transmitted bitwise inverted.
+    //   2) Depending on the endian-ness of your processor, the binary
+    //      representation of the two-byte return value may have a different
+    //      byte order than the two bytes you get from 1-Wire.
+    // @param input - Array of bytes to checksum.
+    // @param len - How many bytes to use.
+    // @param crc - The crc starting value (optional)
+    // @return The CRC16, as defined by Dallas Semiconductor.
+    static uint16_t crc16(const uint8_t* input, uint16_t len, uint16_t crc = 0);
+#endif
+#endif
+};
+
+#endif