diff --git a/ChangeLog b/ChangeLog
index db796073f3..54dbad71b4 100755
--- a/ChangeLog
+++ b/ChangeLog
@@ -12421,3 +12421,5 @@
 	  upper half.  The upper half driver that interacts directly with the
 	  application is the appropriate place to be generating signal
 	  (2016-07-31).
+	* drivers/ioexpander/skeleton.c: Add a skeleton I/O Expander driver
+	  (based on the PCA9555 driver) (2016-07-31).
diff --git a/drivers/ioexpander/skeleton.c b/drivers/ioexpander/skeleton.c
new file mode 100644
index 0000000000..668c57561c
--- /dev/null
+++ b/drivers/ioexpander/skeleton.c
@@ -0,0 +1,730 @@
+/****************************************************************************
+ * drivers/ioexpander/skeleton.c
+ *
+ *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <semaphore.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/ioexpander/ioexpander.h>
+#include <nuttx/ioexpander/skeleton.h>
+
+#include "skeleton.h"
+
+#if defined(CONFIG_IOEXPANDER_skeleton)
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+#ifdef CONFIG_IOEXPANDER_INT_ENABLE
+/* This type represents on registered pin interrupt callback */
+
+struct skel_callback_s
+{
+   ioe_pinset_t pinset;                 /* Set of pin interrupts that will generate
+                                         * the callback. */
+   ioe_callback_t cbfunc;               /* The saved callback function pointer */
+};
+#endif
+
+/* This structure represents the state of the I/O Expander driver */
+
+struct skel_dev_s
+{
+  struct ioexpander_dev_s dev;          /* Nested structure to allow casting as public gpio
+                                         * expander. */
+#ifdef CONFIG_skeleton_MULTIPLE
+  FAR struct skel_dev_s *flink;         /* Supports a singly linked list of drivers */
+#endif
+  sem_t exclsem;                        /* Mutual exclusion */
+
+#ifdef CONFIG_IOEXPANDER_INT_ENABLE
+  struct work_s work;                   /* Supports the interrupt handling "bottom half" */
+
+  /* Saved callback information for each I/O expander client */
+
+  struct skel_callback_s cb[CONFIG_skeleton_INT_NCALLBACKS];
+#endif
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static int skel_direction(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+             int dir);
+static int skel_option(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+             int opt, void *val);
+static int skel_writepin(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+             bool value);
+static int skel_readpin(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+             FAR bool *value);
+static int skel_readbuf(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+             FAR bool *value);
+#ifdef CONFIG_IOEXPANDER_MULTIPIN
+static int skel_multiwritepin(FAR struct ioexpander_dev_s *dev,
+             FAR uint8_t *pins, FAR bool *values, int count);
+static int skel_multireadpin(FAR struct ioexpander_dev_s *dev,
+             FAR uint8_t *pins, FAR bool *values, int count);
+static int skel_multireadbuf(FAR struct ioexpander_dev_s *dev,
+             FAR uint8_t *pins, FAR bool *values, int count);
+#endif
+#ifdef CONFIG_IOEXPANDER_INT_ENABLE
+static int skel_attach(FAR struct ioexpander_dev_s *dev,
+             ioe_pinset_t pinset, ioe_callback_t callback);
+#endif
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+#ifndef CONFIG_skeleton_MULTIPLE
+/* If only a single device is supported, then the driver state structure may
+ * as well be pre-allocated.
+ */
+
+static struct skel_dev_s g_skel;
+
+/* Otherwise, we will need to maintain allocated driver instances in a list */
+
+#else
+static struct skel_dev_s *g_skel_list;
+#endif
+
+/* I/O expander vtable */
+
+static const struct ioexpander_ops_s g_skel_ops =
+{
+  skel_direction,
+  skel_option,
+  skel_writepin,
+  skel_readpin,
+  skel_readbuf
+#ifdef CONFIG_IOEXPANDER_MULTIPIN
+  , skel_multiwritepin
+  , skel_multireadpin
+  , skel_multireadbuf
+#endif
+#ifdef CONFIG_IOEXPANDER_INT_ENABLE
+  , skel_attach
+#endif
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: skel_lock
+ *
+ * Description:
+ *   Get exclusive access to the I/O Expander
+ *
+ ****************************************************************************/
+
+static void skel_lock(FAR struct skel_dev_s *priv)
+{
+  while (sem_wait(&priv->exclsem) < 0)
+    {
+      /* EINTR is the only expected error from sem_wait() */
+
+      DEBUGASSERT(errno == EINTR);
+    }
+}
+
+#define skel_unlock(p) sem_post(&(p)->exclsem)
+
+/****************************************************************************
+ * Name: skel_setbit
+ *
+ * Description:
+ *  Write a bit in a register pair
+ *
+ ****************************************************************************/
+
+static int skel_setbit(FAR struct skel_dev_s *priv, uint8_t pin, int bitval)
+{
+  ioe_pinset_t pinset;
+  int ret;
+
+  if (pin >= CONFIG_IOEXPANDER_NPINS)
+    {
+      return -ENXIO;
+    }
+
+  /* Read the pinset from the IO-Expander hardware */
+#warning Missing logic
+
+  /* Set or clear the pin value */
+
+  if (bitval)
+    {
+      pinset |= (1 << pin);
+    }
+  else
+    {
+      pinset &= ~(1 << pin);
+    }
+
+  /* Write the modified value back to the I/O expander */
+#warning Missing logic
+
+#ifdef CONFIG_IOEXPANDER_RETRY
+  if (ret < 0)
+    {
+      /* Try again (only once) */
+#warning Missing logic
+    }
+#endif
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: skel_getbit
+ *
+ * Description:
+ *  Get a bit from a register pair
+ *
+ ****************************************************************************/
+
+static int skel_getbit(FAR struct skel_dev_s *priv, uint8_t addr,
+                       uint8_t pin, FAR bool *val)
+{
+  ioe_pinset_t pinset;
+  int ret;
+
+  if (pin >= CONFIG_IOEXPANDER_NPINS)
+    {
+      return -ENXIO;
+    }
+
+  /* Read the pinset from the IO-Expander hardware */
+#warning Missing logic
+
+  /* Return true is the corresponding pin is set */
+
+  *val = ((pinset & (1 << pin)) != 0);
+  return OK;
+}
+
+/****************************************************************************
+ * Name: skel_direction
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+static int skel_direction(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+                          int direction)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ret;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+
+  /* Set the pin direction in the I/O Expander */
+#warning Missing logic
+
+  skel_unlock(priv);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: skel_option
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+static int skel_option(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+                       int opt, FAR void *val)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ival = (int)((intptr_t)val);
+  int ret = -EINVAL;
+
+  if (opt == IOEXPANDER_OPTION_INVERT)
+    {
+      /* Get exclusive access to the I/O Expander */
+
+      skel_lock(priv);
+
+      /* Set the pin option */
+#warning Missing logic
+
+      skel_unlock(priv);
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: skel_writepin
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+static int skel_writepin(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+                         bool value)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ret;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+
+  /* Write the pin value */
+#warning Missing logic
+
+  skel_unlock(priv);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: skel_readpin
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+static int skel_readpin(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+                        FAR bool *value)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ret;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+
+  /* Read the pin value */
+#warning Missing logic
+
+  skel_unlock(priv);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: skel_readbuf
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+static int skel_readbuf(FAR struct ioexpander_dev_s *dev, uint8_t pin,
+                        FAR bool *value)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ret;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+
+  /* Read the buffered pin level */
+#warning Missing logic
+
+  skel_unlock(priv);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: skel_getmultibits
+ *
+ * Description:
+ *  Read multiple bits from I/O Expander registers.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_IOEXPANDER_MULTIPIN
+static int skel_getmultibits(FAR struct skel_dev_s *priv, FAR uint8_t *pins,
+                             FAR bool *values, int count)
+{
+  ioe_pinset_t pinset;
+  int pin;
+  int ret = OK;
+  int i;
+
+  /* Read the pinset from the IO-Expander hardware */
+#warning Missing logic
+
+  /* Read the requested bits */
+
+  for (i = 0; i < count; i++)
+    {
+      pin = pins[i];
+      if (pin >= CONFIG_IOEXPANDER_NPINS)
+        {
+          return -ENXIO;
+        }
+
+      values[i] = ((pinset & (1 << pin) != 0);
+    }
+
+  return OK;
+}
+#endif
+
+/****************************************************************************
+ * Name: skel_multiwritepin
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_IOEXPANDER_MULTIPIN
+static int skel_multiwritepin(FAR struct ioexpander_dev_s *dev,
+                                 FAR uint8_t *pins, FAR bool *values,
+                                 int count)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  ioe_pinset_t pinset;
+  int pin;
+  int ret;
+  int i;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+
+  /* Read the pinset from the IO-Expander hardware */
+#warning Missing logic
+
+  /* Apply the user defined changes */
+
+  for (i = 0; i < count; i++)
+    {
+      pin = pins[i];
+      if (pin >= CONFIG_IOEXPANDER_NPINS)
+        {
+          skel_unlock(priv);
+          return -ENXIO;
+        }
+
+      if (values[i])
+        {
+          pinset |= (1 << pin);
+        }
+      else
+        {
+          pinset &= ~(1 << pin);
+        }
+    }
+
+  /* Now write back the new pins states */
+#warning Missing logic
+
+  skel_unlock(priv);
+  return ret;
+}
+#endif
+
+/****************************************************************************
+ * Name: skel_multireadpin
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_IOEXPANDER_MULTIPIN
+static int skel_multireadpin(FAR struct ioexpander_dev_s *dev,
+                                FAR uint8_t *pins, FAR bool *values,
+                                int count)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ret;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+  ret = skel_getmultibits(priv, pins, values, count);
+  skel_unlock(priv);
+  return ret;
+}
+#endif
+
+/****************************************************************************
+ * Name: skel_multireadbuf
+ *
+ * Description:
+ *  See include/nuttx/ioexpander/ioexpander.h
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_IOEXPANDER_MULTIPIN
+static int skel_multireadbuf(FAR struct ioexpander_dev_s *dev,
+                                FAR uint8_t *pins, FAR bool *values,
+                                int count)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ret;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+  ret = skel_getmultibits(priv, pins, values, count);
+  skel_unlock(priv);
+  return ret;
+}
+#endif
+
+/****************************************************************************
+ * Name: skel_attach
+ *
+ * Description:
+ *   Attach a pin interrupt callback function.
+ *
+ * Input Parameters:
+ *   dev      - Device-specific state data
+ *   pinset   - The set of pin events that will generate the callback
+ *   callback - The pointer to callback function.  NULL will detach the
+ *              callback.
+ *
+ * Returned Value:
+ *   0 on success, else a negative error code
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_skeleton_INT_ENABLE
+static int skel_attach(FAR struct ioexpander_dev_s *dev, ioe_pinset_t pinset,
+                       ioe_callback_t callback)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)dev;
+  int ret;
+  int i;
+
+  /* Get exclusive access to the I/O Expander */
+
+  skel_lock(priv);
+
+  /* Find and available in entry in the callback table */
+
+  ret = -ENOSPC;
+  for (i = 0; i < CONFIG_skeleton_INT_NCALLBACKS; i++)
+    {
+       /* Is this entry available (i.e., no callback attached) */
+
+       if (priv->cb[i].cbfunc == NULL)
+         {
+           /* Yes.. use this entry */
+
+           priv->cb[i].pinset = pinset;
+           priv->cb[i].cbfunc = callback;
+           ret = OK;
+         }
+    }
+
+  /* Add this callback to the table */
+
+  skel_unlock(priv);
+  return ret;
+}
+#endif
+
+/****************************************************************************
+ * Name: skel_irqworker
+ *
+ * Description:
+ *   Handle GPIO interrupt events (this function actually executes in the
+ *   context of the worker thread).
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_skeleton_INT_ENABLE
+static void skel_irqworker(void *arg)
+{
+  FAR struct skel_dev_s *priv = (FAR struct skel_dev_s *)arg;
+  ioe_pinset_t pinset;
+  int ret;
+  int i;
+
+  /* Read the pinset from the IO-Expander hardware */
+#warning Missing logic
+
+  /* Perform pin interrupt callbacks */
+
+  for (i = 0; i < CONFIG_skeleton_INT_NCALLBACKS; i++)
+    {
+      /* Is this entry valid (i.e., callback attached)?  If so, did andy of
+       * the requested pin interrupts occur?
+       */
+
+      if (priv->cb[i].cbfunc != NULL)
+        {
+          /* Did any of the requested pin interrupts occur? */
+
+          ioe_pinset_t match = pinset & priv->cb[i].pinset;
+          if (match != 0)
+            {
+              /* Yes.. perform the callback */
+
+              (void)priv->cb[i].cbfunc(&priv->dev, match);
+            }
+        }
+    }
+
+  /* Re-enable interrupts */
+#warning Missing logic
+}
+#endif
+
+/****************************************************************************
+ * Name: skel_interrupt
+ *
+ * Description:
+ *   Handle GPIO interrupt events (this function executes in the
+ *   context of the interrupt).
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_skeleton_INT_ENABLE
+static int skel_interrupt(int irq, FAR void *context)
+{
+#ifdef CONFIG_skeleton_MULTIPLE
+  /* To support multiple devices,
+   * retrieve the priv structure using the irq number.
+   */
+
+#  warning Missing logic
+
+#else
+  register FAR struct skel_dev_s *priv = &g_skel;
+#endif
+
+  /* Defer interrupt processing to the worker thread.  This is not only
+   * much kinder in the use of system resources but is probably necessary
+   * to access the I/O expander device.
+   */
+
+  /* Notice that further GPIO interrupts are disabled until the work is
+   * actually performed.  This is to prevent overrun of the worker thread.
+   * Interrupts are re-enabled in skel_irqworker() when the work is
+   * completed.
+   */
+
+  if (work_available(&priv->work))
+    {
+      /* Disable interrupts */
+#warning Missing logic
+
+      /* Schedule interrupt related work on the high priority worker thread. */
+
+      work_queue(HPWORK, &priv->work, skel_irqworker,
+                 (FAR void *)priv, 0);
+    }
+
+  return OK;
+}
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: skel_initialize
+ *
+ * Description:
+ *   Initialize a I/O Expander device.
+ *
+ * TODO: Actually support more than one device.
+ *
+ ****************************************************************************/
+
+FAR struct ioexpander_dev_s *skel_initialize(void)
+{
+  FAR struct skel_dev_s *priv;
+
+#ifdef CONFIG_skeleton_MULTIPLE
+  /* Allocate the device state structure */
+
+  priv = (FAR struct skel_dev_s *)kmm_zalloc(sizeof(struct skel_dev_s));
+  if (!priv)
+    {
+      return NULL;
+    }
+
+  /* And save the device structure in the list of I/O Expander so that we can
+   * find it later.
+   */
+
+  priv->flink = g_skel_list;
+  g_skel_list = priv;
+
+#else
+  /* Use the one-and-only I/O Expander driver instance */
+
+  priv = &g_skel;
+#endif
+
+  /* Initialize the device state structure */
+
+  priv->dev.ops = &g_skel_ops;
+
+#ifdef CONFIG_skeleton_INT_ENABLE
+  /* Attach the I/O expander interrupt handler and enable interrupts */
+#warning Missing logic
+
+#endif
+
+  sem_init(&priv->exclsem, 0, 1);
+  return &priv->dev;
+}
+
+#endif /* CONFIG_IOEXPANDER_skeleton */