wfs: C port; C++ wraps C

Signed-off-by: Jon Trulson <jtrulson@ics.com>

examples/c++/wfs.cxx

@@ -33,46 +33,47 @@ int shouldRun = true;
 
 void sig_handler(int signo)
 {
-  if (signo == SIGINT)
-    shouldRun = false;
+    if (signo == SIGINT)
+        shouldRun = false;
 }
 
 
 int main()
 {
-  signal(SIGINT, sig_handler);
+    signal(SIGINT, sig_handler);
 
 //! [Interesting]
-  // Instantiate a Water Flow Sensor on digital pin D2
-  upm::WFS* flow = new upm::WFS(2);
-  
-  // set the flow counter to 0 and start counting
-  flow->clearFlowCounter();
-  flow->startFlowCounter();
+    // Instantiate a Water Flow Sensor on digital pin D2.  This must
+    // be an interrupt capable pin.
+    upm::WFS* flow = new upm::WFS(2);
 
-  while (shouldRun)
+    // set the flow counter to 0 and start counting
+    flow->clearFlowCounter();
+    flow->startFlowCounter();
+
+    while (shouldRun)
     {
-      // we grab these (,illis and flowCount) just for display
-      // purposes in this example
-      uint32_t millis = flow->getMillis();
-      uint32_t flowCount = flow->flowCounter();
+        // we grab these (millis and flowCount) just for display
+        // purposes in this example
+        uint32_t millis = flow->getMillis();
+        uint32_t flowCount = flow->flowCounter();
 
-      float fr = flow->flowRate();
+        float fr = flow->flowRate();
 
-      // output milliseconds passed, flow count, and computed flow rate
-      cout << "Millis: " << millis << " Flow Count: " << flowCount;
-      cout << " Flow Rate: " << fr << " LPM" << endl;
+        // output milliseconds passed, flow count, and computed flow rate
+        cout << "Millis: " << millis << " Flow Count: " << flowCount;
+        cout << " Flow Rate: " << fr << " LPM" << endl;
 
-      // best to gather data for at least one second for reasonable
-      // results.
-      sleep(2);
+        // best to gather data for at least one second for reasonable
+        // results.
+        sleep(2);
     }
 
-  flow->stopFlowCounter();
+    flow->stopFlowCounter();
 //! [Interesting]
 
-  cout << "Exiting..." << endl;
+    cout << "Exiting..." << endl;
 
-  delete flow;
-  return 0;
+    delete flow;
+    return 0;
 }

examples/c/CMakeLists.txt

@@ -146,6 +146,7 @@ add_example (max30100)
 add_example (speaker)
 add_example (cjq4435)
 add_example (hmc5883l)
+add_example (wfs)
 
 # Custom examples
 add_custom_example (nmea_gps_i2c-example-c nmea_gps_i2c.c nmea_gps)

examples/c/wfs.c

@@ -0,0 +1,91 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2014-02017 Intel Corporation.
+ *
+ * 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 <unistd.h>
+#include <stdio.h>
+#include <signal.h>
+
+#include <upm_utilities.h>
+#include "wfs.h"
+
+int shouldRun = true;
+
+void sig_handler(int signo)
+{
+    if (signo == SIGINT)
+        shouldRun = false;
+}
+
+
+int main(int argc, char **argv)
+{
+    signal(SIGINT, sig_handler);
+
+//! [Interesting]
+    // Instantiate a Water Flow Sensor on digital pin D2.  This must
+    // be an interrupt capable pin.
+
+    wfs_context sensor = wfs_init(2);
+    if (!sensor)
+    {
+        printf("%s: wfs_init() failed\n", __FUNCTION__);
+        return 1;
+    }
+
+    // set the flow counter to 0 and start counting
+    wfs_clear_flow_counter(sensor);
+    if (wfs_start_flow_counter(sensor))
+    {
+        printf("%s: wfs_start_flow_counter() failed\n", __FUNCTION__);
+        wfs_close(sensor);
+        return 1;
+    }
+
+    while (shouldRun)
+    {
+        // we grab these (millis and flowCount) just for display
+        // purposes in this example
+        uint32_t millis = wfs_get_millis(sensor);
+        uint32_t flowCount = wfs_flow_counter(sensor);
+
+        float fr = wfs_flow_rate(sensor);
+
+        // output milliseconds passed, flow count, and computed flow rate
+        printf("Millis: %8d Flow Count: %5d Flow Rate: %f LPM\n",
+               millis, flowCount, fr);
+
+        // best to gather data for at least one second for reasonable
+        // results.
+        upm_delay(2);
+    }
+
+    wfs_stop_flow_counter(sensor);
+
+    printf("Exiting...\n");
+
+    wfs_close(sensor);
+
+//! [Interesting]
+    return 0;
+}

examples/java/WFSSample.java

@@ -25,20 +25,23 @@
 //NOT TESTED!!!
 public class WFSSample {
 
-	public static void main(String[] args) throws InterruptedException {
-		// ! [Interesting]
-		// Instantiate a Water Flow Sensor on digital pin D2
-		upm_wfs.WFS flow = new upm_wfs.WFS(2);
+    public static void main(String[] args) throws InterruptedException {
+// ! [Interesting]
 
-		flow.clearFlowCounter();
-		flow.startFlowCounter();
+        // Instantiate a Water Flow Sensor on
+        // digital pin D2.  This must be an
+        // interrupt capable pin.
+        upm_wfs.WFS flow = new upm_wfs.WFS(2);
 
-		while (true) {
-			System.out.print("Millis: " + flow.getMillis() + " FlowCount: " + flow.flowCounter());
-			System.out.println(" Flow Rate: " + flow.flowRate() + " LPM");
+        flow.clearFlowCounter();
+        flow.startFlowCounter();
 
-			Thread.sleep(2000);
-		}
-		// ! [Interesting]
-	}
+        while (true) {
+            System.out.print("Millis: " + flow.getMillis() + " FlowCount: " + flow.flowCounter());
+            System.out.println(" Flow Rate: " + flow.flowRate() + " LPM");
+
+            Thread.sleep(2000);
+        }
+// ! [Interesting]
+    }
 }

examples/javascript/wfs.js

@@ -24,7 +24,8 @@
 
 var waterFlow_lib = require('jsupm_wfs');
 
-// Instantiate a Water Flow Sensor on digital pin D2
+// Instantiate a Water Flow Sensor on digital pin D2.  This must be an
+// interrupt capable pin.
 var myWaterFlow_obj = new waterFlow_lib.WFS(2);
 
 // set the flow counter to 0 and start counting

examples/python/wfs.py

@@ -26,7 +26,8 @@ import time, sys, signal, atexit
 from upm import pyupm_wfs as upmwfs
 
 def main():
-    # Instantiate a Water Flow Sensor on digital pin D2
+    # Instantiate a Water Flow Sensor on digital pin D2.  This must be
+    # an interrupt capable GPIO.
     myWaterFlow = upmwfs.WFS(2)
 
     ## Exit handlers ##

src/wfs/CMakeLists.txt

@@ -1,5 +1,8 @@
 upm_mixed_module_init (NAME wfs
-    DESCRIPTION "Water flow sensor (WFS)"
+    DESCRIPTION "WFS (Water Flow Sensor)"
+    C_HDR wfs.h
+    C_SRC wfs.c
     CPP_HDR wfs.hpp
     CPP_SRC wfs.cxx
+    CPP_WRAPS_C
     REQUIRES mraa)

src/wfs/wfs.c

@@ -0,0 +1,152 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * 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 <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#include "wfs.h"
+
+// interrupt handler
+static void wfs_flow_isr(void *ctx)
+{
+    assert(ctx != NULL);
+
+    wfs_context dev = (wfs_context)ctx;
+
+    dev->flowCounter++;
+}
+
+wfs_context wfs_init(int pin)
+{
+    // make sure MRAA is initialized
+    int mraa_rv;
+    if ((mraa_rv = mraa_init()) != MRAA_SUCCESS)
+    {
+        printf("%s: mraa_init() failed (%d).\n", __FUNCTION__, mraa_rv);
+        return NULL;
+    }
+
+    wfs_context dev =
+        (wfs_context)malloc(sizeof(struct _wfs_context));
+
+    if (!dev)
+        return NULL;
+
+    // zero out context
+    memset((void *)dev, 0, sizeof(struct _wfs_context));
+
+    if ( !(dev->gpio = mraa_gpio_init(pin)) )
+    {
+        printf("%s: mraa_gpio_init() failed.\n", __FUNCTION__);
+        wfs_close(dev);
+        return NULL;
+    }
+
+    mraa_gpio_dir(dev->gpio, MRAA_GPIO_IN);
+
+    wfs_init_clock(dev);
+
+    return dev;
+}
+
+void wfs_close(wfs_context dev)
+{
+    assert(dev != NULL);
+
+    if (dev->isrInstalled)
+        wfs_stop_flow_counter(dev);
+
+    if (dev->gpio)
+        mraa_gpio_close(dev->gpio);
+
+    free(dev);
+}
+
+void wfs_init_clock(const wfs_context dev)
+{
+    assert(dev != NULL);
+
+    upm_clock_init(&dev->clock);
+}
+
+uint32_t wfs_get_millis(const wfs_context dev)
+{
+    assert(dev != NULL);
+
+    return upm_elapsed_ms(&dev->clock);
+}
+
+void wfs_clear_flow_counter(const wfs_context dev)
+{
+    assert(dev != NULL);
+
+    dev->flowCounter = 0;
+}
+
+upm_result_t wfs_start_flow_counter(const wfs_context dev)
+{
+    assert(dev != NULL);
+
+    wfs_init_clock(dev);
+
+    // install our interrupt handler
+    if (mraa_gpio_isr(dev->gpio, MRAA_GPIO_EDGE_RISING,
+                      &wfs_flow_isr, dev))
+    {
+        printf("%s: mraa_gpio_isr() failed.\n", __FUNCTION__);
+        return UPM_ERROR_OPERATION_FAILED;
+    }
+
+    dev->isrInstalled = true;
+    return UPM_SUCCESS;
+}
+
+void wfs_stop_flow_counter(const wfs_context dev)
+{
+    assert(dev != NULL);
+
+    // remove the interrupt handler
+    mraa_gpio_isr_exit(dev->gpio);
+
+    dev->isrInstalled = false;
+}
+
+uint32_t wfs_flow_counter(const wfs_context dev)
+{
+    assert(dev != NULL);
+
+    return dev->flowCounter;
+}
+
+float wfs_flow_rate(const wfs_context dev)
+{
+    assert(dev != NULL);
+
+    uint32_t millis = wfs_get_millis(dev);
+    uint32_t flow = wfs_flow_counter(dev);
+
+    // 7.5 comes from the seeedstudio page, see the confusing datasheet :)
+    return ((float)flow * 7.5) / ( ((float)millis / 1000.0) * 60.0);
+}

src/wfs/wfs.cxx

@@ -1,6 +1,6 @@
 /*
  * Author: Jon Trulson <jtrulson@ics.com>
- * Copyright (c) 2015 Intel Corporation.
+ * Copyright (c) 2015-2017 Intel Corporation.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -31,94 +31,42 @@
 using namespace upm;
 using namespace std;
 
-WFS::WFS(int pin)
+WFS::WFS(int pin) :
+    m_wfs(wfs_init(pin))
 {
-  if ( !(m_gpio = mraa_gpio_init(pin)) )
-    {
-      throw std::invalid_argument(std::string(__FUNCTION__) +
-                                  ": mraa_gpio_init() failed, invalid pin?");
-      return;
-    }
-
-  mraa_gpio_dir(m_gpio, MRAA_GPIO_IN);
-
-  initClock();
-  m_flowCounter = 0;
-  m_isrInstalled = false;
+    if (!m_wfs)
+        throw std::runtime_error(std::string(__FUNCTION__) +
+                                 ": wfs_init() failed");
 }
 
 WFS::~WFS()
 {
-  if (m_isrInstalled)
-    stopFlowCounter();
-
-  mraa_gpio_close(m_gpio);
+    wfs_close(m_wfs);
 }
 
 void WFS::initClock()
 {
-  gettimeofday(&m_startTime, NULL);
+    wfs_init_clock(m_wfs);
 }
 
 uint32_t WFS::getMillis()
 {
-  struct timeval elapsed, now;
-  uint32_t elapse;
-
-  // get current time
-  gettimeofday(&now, NULL);
-
-  // compute the delta since m_startTime
-  if( (elapsed.tv_usec = now.tv_usec - m_startTime.tv_usec) < 0 ) 
-    {
-      elapsed.tv_usec += 1000000;
-      elapsed.tv_sec = now.tv_sec - m_startTime.tv_sec - 1;
-    } 
-  else 
-    {
-      elapsed.tv_sec = now.tv_sec - m_startTime.tv_sec;
-    }
-
-  elapse = (uint32_t)((elapsed.tv_sec * 1000) + (elapsed.tv_usec / 1000));
-
-  // never return 0
-  if (elapse == 0)
-    elapse = 1;
-
-  return elapse;
+    return wfs_get_millis(m_wfs);
 }
 
 void WFS::startFlowCounter()
 {
-  initClock();
-  // install our interrupt handler
-  mraa_gpio_isr(m_gpio, MRAA_GPIO_EDGE_RISING, 
-                &flowISR, this);
-
-  m_isrInstalled = true;
+    if (wfs_start_flow_counter(m_wfs))
+        throw std::runtime_error(std::string(__FUNCTION__) +
+                                 ": wfs_start_flow_counter() failed");
 }
 
 void WFS::stopFlowCounter()
 {
-  // remove the interrupt handler
-  mraa_gpio_isr_exit(m_gpio);
-
-  m_isrInstalled = false;
-}
-
-void WFS::flowISR(void *ctx)
-{
-  upm::WFS *This = (upm::WFS *)ctx;
-  This->m_flowCounter++;
+    wfs_stop_flow_counter(m_wfs);
 }
 
 float WFS::flowRate()
 {
-  uint32_t millis = getMillis();
-  uint32_t flow = flowCounter();
-  
-  // 7.5 comes from the seeedstudio page, see the confusing datasheet :)
-  float flowRate = (float(flow) * 7.5) / ((float(millis) / 1000.0) * 60.0);
-
-  return flowRate;
+    return wfs_flow_rate(m_wfs);
 }

src/wfs/wfs.h

@@ -0,0 +1,134 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2017 Intel Corporation.
+ *
+ * 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.
+ */
+#pragma once
+
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <upm.h>
+#include <upm_utilities.h>
+#include <mraa/gpio.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+    /**
+     * @file wfs.h
+     * @library wfs
+     * @brief WFS (Water Flow Sensor)
+     *
+     */
+
+    /**
+     * Device context
+     */
+    typedef struct _wfs_context {
+        mraa_gpio_context gpio;
+
+        volatile uint32_t flowCounter;
+        upm_clock_t       clock;
+        bool              isrInstalled;
+    } *wfs_context;
+
+    /**
+     * Initialize a WFS device
+     *
+     * @param pin GPIO pin to use.  This must be an interrupt capable
+     * pin.
+     * @return Device context, or NULL on error
+     */
+    wfs_context wfs_init(int pin);
+
+    /**
+     * WFS close function
+     *
+     * @param dev Device context
+     */
+    void wfs_close(wfs_context dev);
+
+    /**
+     * Returns the number of milliseconds elapsed since wfs_init_clock()
+     * was last called.
+     *
+     * @param dev Device context
+     * @return Elapsed milliseconds
+     */
+    uint32_t wfs_get_millis(const wfs_context dev);
+
+    /**
+     * Resets the clock
+     *
+     * @param dev Device context
+     */
+    void wfs_init_clock(const wfs_context dev);
+
+    /**
+     * Resets the flow counter to 0. The flow counter should be
+     * stopped via stopFlowCounter() prior to calling this function.
+     *
+     * @param dev Device context
+     */
+    void wfs_clear_flow_counter(const wfs_context dev);
+
+    /**
+     * Starts the flow counter
+     *
+     * @param dev Device context
+     * @return UPM result
+     */
+    upm_result_t wfs_start_flow_counter(const wfs_context dev);
+
+    /**
+     * Stops the flow counter
+     *
+     * @param dev Device context
+     */
+    void wfs_stop_flow_counter(const wfs_context dev);
+
+    /**
+     * Gets the flow counter
+     *
+     * @param dev Device context
+     * @return Flow counter
+     */
+    uint32_t wfs_flow_counter(const wfs_context dev);
+
+    /**
+     * Computes the flow rate in liters per minute (LPM).  Note, this
+     * is for the Grove WFS.  If you are using some other WFS, you
+     * should compute the flow rate on your own based on the data for
+     * your sensor.
+     *
+     * @param dev Device context
+     * @return Computed flow rate in liters per minute
+     */
+    float wfs_flow_rate(const wfs_context dev);
+
+
+#ifdef __cplusplus
+}
+#endif

src/wfs/wfs.hpp

@@ -1,6 +1,6 @@
 /*
  * Author: Jon Trulson <jtrulson@ics.com>
- * Copyright (c) 2015 Intel Corporation.
+ * Copyright (c) 2015-2017 Intel Corporation.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -23,119 +23,113 @@
  */
 #pragma once
 
-#include <string>
-#include <stdint.h>
-#include <sys/time.h>
-#include <mraa/gpio.h>
+#include "wfs.h"
 
 namespace upm {
 
-  /**
-   * @brief Grove Water Flow Sensor library
-   * @defgroup wfs libupm-wfs
-   * @ingroup seeed gpio liquid eak
-   */
-
-  /**
-   * @library wfs
-   * @sensor wfs
-   * @comname Water Flow Sensor
-   * @altname Grove Water Flow Sensor
-   * @type liquid
-   * @man seeed
-   * @web http://www.seeedstudio.com/wiki/index.php?title=G1/2_Water_Flow_sensor
-   * @con gpio
-   * @kit eak
-
-   * @brief API for the Grove Water Flow Sensor
-   *
-   * This sensor is used to measure water flow in liters per
-   * minute (LPM). It incorporates a Hall Effect sensor. The UPM module
-   * defines an interrupt routine to be triggered on each low pulse,
-   * keeping count. This device requires a 10K pull-up resistor for
-   * the signal line (yellow wire). There is a schematic diagram on
-   * the SeeedStudio site (3/2015):
-   * http://www.seeedstudio.com/wiki/index.php?title=G1/2_Water_Flow_sensor
-   *
-   * However, be careful when wiring this up - the schematic appears to
-   * have a bug in it: the lower left connection of the signal line
-   * (yellow) to Vcc (red) should not be there. The sensor can work
-   * with this connection, but probably not for very long.
-   *
-   * @image html wfs.jpg
-   * @snippet wfs.cxx Interesting
-   */
-  class WFS {
-  public:
     /**
-     * Grove Water Flow sensor constructor
+     * @brief Grove Water Flow Sensor library
+     * @defgroup wfs libupm-wfs
+     * @ingroup seeed gpio liquid eak
+     */
+
+    /**
+     * @library wfs
+     * @sensor wfs
+     * @comname Water Flow Sensor
+     * @altname Grove Water Flow Sensor
+     * @type liquid
+     * @man seeed
+     * @web http://www.seeedstudio.com/wiki/index.php?title=G1/2_Water_Flow_sensor
+     * @con gpio
+     * @kit eak
+
+     * @brief API for the Grove Water Flow Sensor
      *
-     * @param pin Digital pin to use
-     */
-    WFS(int pin);
-    /**
-     * WFS destructor
-     */
-    ~WFS();
-    /**
-     * Returns the number of milliseconds elapsed since initClock()
-     * was last called.
+     * This sensor is used to measure water flow in liters per
+     * minute (LPM). It incorporates a Hall Effect sensor. The UPM module
+     * defines an interrupt routine to be triggered on each low pulse,
+     * keeping count. This device requires a 10K pull-up resistor for
+     * the signal line (yellow wire). There is a schematic diagram on
+     * the SeeedStudio site (3/2015):
+     * http://www.seeedstudio.com/wiki/index.php?title=G1/2_Water_Flow_sensor
      *
-     * @return Elapsed milliseconds
-     */
-    uint32_t getMillis();
-
-    /**
-     * Resets the clock
+     * However, be careful when wiring this up - the schematic appears to
+     * have a bug in it: the lower left connection of the signal line
+     * (yellow) to Vcc (red) should not be there. The sensor can work
+     * with this connection, but probably not for very long.
      *
+     * @image html wfs.jpg
+     * @snippet wfs.cxx Interesting
      */
-    void initClock();
+    class WFS {
+    public:
+        /**
+         * Grove Water Flow sensor constructor
+         *
+         * @param pin GPIO pin to use.  This must be an interrupt
+         * capable pin.
+         */
+        WFS(int pin);
 
-    /**
-     * Resets the flow counter to 0. The flow counter should be
-     * stopped via stopFlowCounter() prior to calling this function.
-     *
-     */
-    void clearFlowCounter() { m_flowCounter = 0; };
+        /**
+         * WFS destructor
+         */
+        ~WFS();
 
-    /**
-     * Starts the flow counter
-     *
-     */
-    void startFlowCounter();
+        /**
+         * Returns the number of milliseconds elapsed since initClock()
+         * was last called.
+         *
+         * @return Elapsed milliseconds
+         */
+        uint32_t getMillis();
 
-    /**
-     * Stops the flow counter
-     *
-     */
-    void stopFlowCounter();
+        /**
+         * Resets the clock
+         *
+         */
+        void initClock();
 
-    /**
-     * Gets the flow counter
-     *
-     * @return Flow counter
-     */
-    uint32_t flowCounter() { return m_flowCounter; };
+        /**
+         * Resets the flow counter to 0. The flow counter should be
+         * stopped via stopFlowCounter() prior to calling this function.
+         *
+         */
+        void clearFlowCounter() { wfs_clear_flow_counter(m_wfs); };
 
-    /**
-     * Computes the flow rate in liters per minute (LPM)
-     *
-     * @return Computed flow rate
-     */
-    float flowRate();
+        /**
+         * Starts the flow counter
+         *
+         */
+        void startFlowCounter();
 
-  private:
-    /**
-     * Flow interrupt service routine (ISR)
-     *
-     */
-    static void flowISR(void *ctx);
+        /**
+         * Stops the flow counter
+         *
+         */
+        void stopFlowCounter();
 
-    volatile uint32_t m_flowCounter;
-    struct timeval m_startTime;
-    mraa_gpio_context m_gpio;
-    bool m_isrInstalled;
-  };
+        /**
+         * Gets the flow counter
+         *
+         * @return Flow counter
+         */
+        uint32_t flowCounter() { return wfs_flow_counter(m_wfs); };
+
+        /**
+         * Computes the flow rate in liters per minute (LPM).  Note, this
+         * is for the Grove WFS.  If you are using some other WFS, you
+         * should compute the flow rate on your own based on the data for
+         * your sensor.
+         *
+         * @return Computed flow rate
+         */
+        float flowRate();
+
+    protected:
+        wfs_context m_wfs;
+
+    private:
+    };
 }
-
-