abstract out the UBlox GPS driver

src/gps/UBloxGPS.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include "GPS.h"
+#include "Observer.h"
+#include "PeriodicTask.h"
+#include "SparkFun_Ublox_Arduino_Library.h"
+
+/**
+ * A gps class that only reads from the GPS periodically (and FIXME - eventually keeps the gps powered down except when reading)
+ *
+ * When new data is available it will notify observers.
+ */
+class UBloxGPS : public GPS, public PeriodicTask
+{
+    SFE_UBLOX_GPS ublox;
+
+    bool wantNewLocation = true;
+
+    CallbackObserver<UBloxGPS, void *> notifySleepObserver = CallbackObserver<UBloxGPS, void *>(this, &UBloxGPS::prepareSleep);
+
+  public:
+    UBloxGPS();
+
+    /**
+     * Returns true if we succeeded
+     */
+    virtual bool setup();
+
+    virtual void doTask();
+
+    /**
+     * Restart our lock attempt - try to get and broadcast a GPS reading ASAP
+     * called after the CPU wakes from light-sleep state */
+    virtual void startLock();
+
+  private:
+
+    /// Prepare the GPS for the cpu entering deep or light sleep, expect to be gone for at least 100s of msecs
+    /// always returns 0 to indicate okay to sleep
+    int prepareSleep(void *unused);
+};