Two-wire version of the I2C bus master

libraries/I2C/BitBangI2C.cpp

@@ -29,11 +29,13 @@
  *
  * This class implements the I2C master protocol on any arbitrary pair
  * of data and clock pins.  It is not restricted to pre-defined pins as
- * is the case for the standard \c Wire library.
+ * is the case for WireI2C.
  *
  * This implementation only implements the master side of the protocol.
  * It assumes that there is a single bus master, no arbitration, and
  * no clock stretching.
+ *
+ * \sa I2CMaster, WireI2C
  */
 
 #define i2cDelay()  delayMicroseconds(5)

libraries/I2C/I2CMaster.cpp

@@ -26,7 +26,7 @@
  * \class I2CMaster I2CMaster.h <I2CMaster.h>
  * \brief Abstract base class for I2C master implementations.
  *
- * \sa I2CMaster
+ * \sa BitBangI2C, WireI2C
  */
 
 /**

libraries/I2C/WireI2C.cpp

@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2012 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "WireI2C.h"
+#include <WProgram.h>
+
+namespace wireI2C {
+// XXX: Apparently Arduino libraries cannot directly include each other,
+// so we need to work around that by directly pulling in the twi code.
+// We hide it in its own namespace just in case the application uses
+// Wire directly.  Take advantage of the include path to find the
+// system-installed twi library.
+#include "../../../../libraries/Wire/utility/twi.c"
+};
+
+#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
+#define SDA_PIN 20
+#define SCL_PIN 21
+#else
+#define SDA_PIN A4
+#define SCL_PIN A5
+#endif
+
+/**
+ * \class WireI2C WireI2C.h <WireI2C.h>
+ * \brief Implementation of an I2C master using the Arduino two-wire interface.
+ *
+ * This class implements the I2C master protocol on pre-defined DATA and
+ * CLOCK pins (A4 and A5 on most boards, D20 and D21 for Arduino Mega).
+ * For other non-standard pins, use the BitBangI2C class instead.
+ *
+ * This implementation only implements the master side of the protocol.
+ * Use the standard Arduino Wire library for slave I2C implementations.
+ *
+ * \sa I2CMaster, BitBangI2C
+ */
+
+/**
+ * \brief Constructs a new I2C bus master using the Arduino two-wire interface.
+ *
+ * If \a useInternalPullups is true (the default) then internal pullups
+ * will be enabled on the DATA and CLOCK pins.  If \a useInternalPullups
+ * is false, then the external circuit will need to provide pullup resistors.
+ */
+WireI2C::WireI2C(bool useInternalPullups)
+    : slaveAddr(0xFF)
+    , buflen(0)
+    , bufposn(0)
+{
+    pinMode(SDA_PIN, INPUT);
+    pinMode(SCL_PIN, INPUT);
+    if (useInternalPullups) {
+        digitalWrite(SDA_PIN, HIGH);
+        digitalWrite(SCL_PIN, HIGH);
+    }
+    wireI2C::twi_init();
+}
+
+unsigned int WireI2C::maxTransferSize() const
+{
+    return sizeof(buffer);
+}
+
+void WireI2C::startWrite(unsigned int address)
+{
+    slaveAddr = (uint8_t)address;
+    buflen = 0;
+}
+
+void WireI2C::write(uint8_t value)
+{
+    if (buflen < sizeof(buffer))
+        buffer[buflen++] = value;
+}
+
+bool WireI2C::endWrite()
+{
+    uint8_t result = wireI2C::twi_writeTo(slaveAddr, buffer, buflen, 1);
+    slaveAddr = 0xFF;
+    return result == 0;
+}
+
+bool WireI2C::startRead(unsigned int address, unsigned int count)
+{
+    if (slaveAddr != 0xFF) {
+        // There is a write operation open, so flush it first.
+        if (!endWrite())
+            return false;
+    }
+    if (count > sizeof(buffer))
+        count = sizeof(buffer);
+    bufposn = 0;
+    buflen = wireI2C::twi_readFrom((uint8_t)address, buffer, (uint8_t)count);
+    return true;
+}
+
+unsigned int WireI2C::available()
+{
+    return buflen - bufposn;
+}
+
+uint8_t WireI2C::read()
+{
+    if (bufposn < buflen)
+        return buffer[bufposn++];
+    else
+        return 0;
+}

libraries/I2C/WireI2C.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2012 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef WireI2C_h
+#define WireI2C_h
+
+#include "I2CMaster.h"
+
+class WireI2C : public I2CMaster {
+public:
+    explicit WireI2C(bool useInternalPullups = true);
+
+    unsigned int maxTransferSize() const;
+
+    void startWrite(unsigned int address);
+    void write(uint8_t value);
+    bool endWrite();
+
+    bool startRead(unsigned int address, unsigned int count);
+    unsigned int available();
+    uint8_t read();
+
+private:
+    uint8_t slaveAddr;
+    uint8_t buffer[32];
+    uint8_t buflen;
+    uint8_t bufposn;
+};
+
+#endif