Reduce I2C clock speed by factor 2 to workaround Broadcom 2853 I2C cl…

…ock timing bug.

lib/libi2c/BroadcomI2C.cpp

@@ -37,6 +37,9 @@ BroadcomI2C::Result BroadcomI2C::initialize()
     // Set GPIO pins to ALT0 function for SDA, SCL pins
     m_gpio.setAltFunction(2, BroadcomGPIO::Function0);
     m_gpio.setAltFunction(3, BroadcomGPIO::Function0);
+
+    // Set a slow clock to attempt workaround the I2C bug in Broadcom 2835
+    setClockDivider(0x5dc * 2);
     NOTICE("I2C GPIO pins set");
     NOTICE("ClockDivider is " << m_io.read(ClockDivider));
     NOTICE("Status is " << m_io.read(Status));
@@ -52,6 +55,12 @@ BroadcomI2C::Result BroadcomI2C::setAddress(Address addr)
     return Success;
 }
 
+BroadcomI2C::Result BroadcomI2C::setClockDivider(Size divider)
+{
+    m_io.write(ClockDivider, divider);
+    return Success;
+}
+
 BroadcomI2C::Result BroadcomI2C::write(u8 *buf, Size size)
 {
     if (size > FIFOSize)

lib/libi2c/BroadcomI2C.h

@@ -33,6 +33,9 @@
  *
  * @see BCM2835 ARM Peripherals.pdf
  * @see http://www.airspayce.com/mikem/bcm2835/
+ * @see https://github.com/raspberrypi/linux/issues/254
+ * @see https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=13771&start=25
+ * @see http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
  */
 class BroadcomI2C : public I2C
 {
@@ -103,6 +106,14 @@ class BroadcomI2C : public I2C
      */
     virtual Result initialize();
 
+    /**
+     * Set clock divider.
+     *
+     * @param divider Clock divider to use.
+     * @return Result code.
+     */
+    virtual Result setClockDivider(Size divider);
+
     /**
      * Set Slave address.
      *