Diff: GPSProvider.h

Revision:

0:792e9343fd39

Child:

1:c1122f8eec82

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/GPSProvider.h	Thu Oct 30 14:42:27 2014 +0000
@@ -0,0 +1,242 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2014 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __GPS_PROVIDER_H__
+#define __GPS_PROVIDER_H__
+
+class GPSProviderImplBase; /* forward declaration */
+extern GPSProviderImplBase *createGPSProviderInstance(void);
+
+//
+// Here's a snippet showing how this API can be used. Please note that this is
+// an asynchronous API--users can setup an asynchronous handler to receive
+// location updates. The handler gets invoked from interrupt context. Users
+// *should not* do any long running or blocking operations in the handler.
+//
+//      void handleGPSData(const LocationUpdateParams_t *newData) {
+//          /* Do something with the location update; but please don't make any
+//           * blocking calls or invoke long-running operations. */
+//      }
+//
+//      GPSProvider gps;
+//
+//      gps.setPowerMode(LOW_POWER);
+//      gps.onLocationUpdate(handleGPSData);
+//
+//      gps.reset(); // implicitly calls powerOn().
+//      gps.start();
+//
+//      wait(/* some duration to allow controller to stabilize */);
+//      if (gps.haveDeviceInfo()) {
+//          printf("%s", gps.getDeviceInfo());
+//      }
+//
+//      ...
+//      /* Period where the gps locationHandler gets invoked asynchronously. */
+//      ...
+//
+//      /* at some point in the future, either the following.. */
+//      gps.stop();
+//      gps.powerOff();
+//      /* or simply destroy the gps object to achieve the same. */
+//
+
+class GPSProvider {
+public:
+    /** Power mode selection */
+    enum PowerMode_t {
+         POWER_FULL,
+         POWER_LOW,
+    };
+
+    /**
+     * GPS time starts from UTC 01/06/1980(MM/DD/YYYY) and includes 2 fields:
+     * week and tow. For a given GPS time, week is the passed week number since
+     * the GPS start time, and tow(time of week) is the passed seconds since the
+     * last Sunday. For example, a given UTC time [10/30/3014
+     * 01:10:00](MM/DD/YYYY HH:MM:SS) can be converted into GPS time [1816,
+     * 4200](week, seconds).
+     *
+     * GPS time can be used as a quite accurate time once position is fixed.
+     */
+    struct GPSTime_t {
+        uint16_t gps_week;
+        uint32_t tow;       /* time of week (in seconds) */
+    };
+
+    typedef float LocationType_t;
+    typedef float Altitude_t;
+    struct LocationUpdateParams_t {
+        uint32_t       version; /* Layout-version for the following structure;
+                                 * this is to accommodate changes over time. */
+        LocationType_t lat;
+        LocationType_t lon;
+        Altitude_t     altitude;
+
+        union {
+            GPSTime_t gpsTime;
+            float     utcTime;
+        } u;
+    };
+
+public:
+    /**
+     * Set the operating mode for power. Typically this allows the user to
+     * choose between various low-power modes. Entering low-power modes often
+     * results in a trade-off between accuracy and power consumption.
+     *
+     * The new mode takes effect upon calling start().
+     *
+     * @param power The new power mode.
+     * @return      true if the update was successful.
+     */
+    bool setPowerMode(PowerMode_t power);
+
+    /**
+     * HW reset to get location chip into hibernation mode, but in readiness for
+     * starting operation. The GPS controller emerges from hibernation when
+     * start() is called.
+     *
+     * The typical initialization sequence is:
+     *   reset();
+     *   start(); // and thereafter receive location-update callbacks.
+     */
+    void reset(void);
+
+    /**
+     * Start the GPS operation, taking into account the operation mode set
+     * previously. Following this call, the user may expect to receive location
+     * notifications in interrupt context if a handler has previously been set.
+     *
+     * @note: calling start repeatedly doesn't hurt.
+     */
+    void start(void);
+
+    /**
+     * Stop active operation of the GPS; and put it to hibernation.
+     *
+     * @note: You don't need to call reset() afterwards to enter hibernation.
+     * @note: Calling stop() repeatedly doesn't hurt.
+     */
+    void stop(void);
+
+    /**
+     * @return  true if the initialization process has received enough
+     *     information to determine the hardware's version/device-info.
+     */
+    bool haveDeviceInfo(void) const {
+        return discoveredDeviceInfo;
+    }
+
+    /**
+     * Fetch the device information string. This is expected to contain the
+     * version number or any other device identifier.
+     */
+    const char *getDeviceInfo(void) const {
+        return deviceInfo;
+    }
+
+    /**
+     * This is a wildcard API for sending controller specific commands. Use of
+     * this API will make programs non-portable, but then there may arise a
+     * genuine need to access special functionality.
+     *
+     * @param  command   A controller specific command.
+     * @param  arg       Argument to the command; interpreted according to the command.
+     * @return           any return from the command.
+     */
+    uint32_t ioctl(uint32_t command, void *arg);
+
+    /**
+     * @return  true if we've obtained at least one valid location since last
+     *     calling start().
+     *
+     * @Note: This is cleared after reset().
+     */
+    bool locationAvailable(void) const {
+        return haveValidLocation;
+    }
+
+    /**
+     * @return  the last valid location if there is any; else NULL.
+     */
+    const LocationUpdateParams_t *getLastLocation(void) const {
+        return haveValidLocation ? &lastLocation : NULL;
+    }
+
+    /**
+     * Type declaration for a callback to be invoked from interrupt context upon
+     * receiving new location data.
+     *
+     * @Note: Please note that the handler gets invoked from interrupt context.
+     * Users *should not* do any long running or blocking operations in the
+     * handler.
+     */
+    typedef void (* LocationUpdateCallback_t)(const LocationUpdateParams_t *params);
+
+    /**
+     * Setup the locationUpdate callback.
+     *
+     * @Note: Please note that the handler gets invoked from interrupt context.
+     * Users *should not* do any long running or blocking operations in the
+     * handler.
+     */
+    void onLocationUpdate(LocationUpdateCallback_t callback);
+
+public:
+    /**
+     * Default constructor.
+     */
+    GPSProvider() :
+        impl(createGPSProviderInstance()),
+        havePoweredOn(false),
+        discoveredDeviceInfo(false),
+        haveValidLocation(false),
+        deviceInfo(NULL),
+        updateCallback(NULL) {
+        /* empty */
+    }
+
+    virtual ~GPSProvider() {
+        stop();
+    }
+
+private:
+    /**
+     * We use 'composition' to combine a driver-implementation object to the
+     * GPSProvider interface. The implementation object will come to life
+     * through the createGPSProviderInstance(), which must be defined by the
+     * driver library. The mechanics of the implementation are to be hidden
+     * behind the abstract interface provided by GPSProvider.
+     */
+    GPSProviderImplBase *const impl;
+
+private:
+    bool                      havePoweredOn;
+    bool                      discoveredDeviceInfo;
+    bool                      haveValidLocation;
+
+    const char               *deviceInfo;
+    LocationUpdateParams_t    lastLocation;
+    LocationUpdateCallback_t *updateCallback;
+
+    /* disallow copy constructor and assignment operators */
+private:
+    GPSProvider(const GPSProvider&);
+    GPSProvider & operator= (const GPSProvider&);
+};
+
+#endif /*__GPS_PROVIDER_H__*/