Add a bus reset on I2C error. Also add a mechanism for automated retries of operations.

apps/drivers/device/i2c.cpp

@@ -53,6 +53,7 @@ I2C::I2C(const char *name,
 	CDev(name, devname, irq),
 	// public
 	// protected
+	_retries(0),
 	// private
 	_bus(bus),
 	_address(address),
@@ -117,8 +118,10 @@ I2C::transfer(uint8_t *send, unsigned send_len, uint8_t *recv, unsigned recv_len
 	struct i2c_msg_s msgv[2];
 	unsigned msgs;
 	int ret;
+	unsigned tries;
 
-//	debug("transfer out %p/%u  in %p/%u", send, send_len, recv, recv_len);
+	do {
+	//	debug("transfer out %p/%u  in %p/%u", send, send_len, recv, recv_len);
 
 		msgs = 0;
 
@@ -143,7 +146,16 @@ I2C::transfer(uint8_t *send, unsigned send_len, uint8_t *recv, unsigned recv_len
 
 		ret = I2C_TRANSFER(_dev, &msgv[0], msgs);
 
+		if (ret == OK)
+			break;
+		
+		// reset the I2C bus to unwedge on error
+		up_i2creset(_dev);
+
+	} while (tries++ < _retries);
+
 	return ret;
+
 }
 
 } // namespace device

apps/drivers/device/i2c.h

@@ -52,6 +52,12 @@ class __EXPORT I2C : public CDev
 {
 
 protected:
+	/**
+	 * The number of times a read or write operation will be retried on
+	 * error.
+	 */
+	unsigned		_retries;
+
 	/**
 	 * @ Constructor
 	 *