reorganization of uart-based receiver drivers

FEATURE_SPEKTRUM has been removed and replaced with FEATURE_SERIALRX.
cli  option serialrx_type now configures what type of receiver it is
0 = spektrum1024, 1 = spektrum2048, 2 = sbus
sbus will need hardware inverter to use.
also cleaned up receiver drivers to assign readrawRC callback instead of assigning in code in main()
none of this has been tested.

git-svn-id: https://afrodevices.googlecode.com/svn/trunk/baseflight@418 7c89a4a9-59b9-e629-4cfe-3a2d53b20e61

src/mw.c

@@ -436,14 +436,26 @@ void loop(void)
     static uint8_t GPSNavReset = 1;
     bool isThrottleLow = false;
 
-    // this will return false if spektrum is disabled. shrug.
-    if (spektrumFrameComplete())
-        computeRC();
+    // calculate rc stuff from serial-based receivers (spek/sbus)
+    if (feature(FEATURE_SERIALRX)) {
+        bool ready = false;
+        switch (mcfg.serialrx_type) {
+            case SERIALRX_SPEKTRUM1024:
+            case SERIALRX_SPEKTRUM2048:
+                ready = spektrumFrameComplete();
+                break;
+            case SERIALRX_SBUS:
+                ready = sbusFrameComplete();
+                break;
+        }
+        if (ready)
+            computeRC();
+    }
 
     if ((int32_t)(currentTime - rcTime) >= 0) { // 50Hz
         rcTime = currentTime + 20000;
         // TODO clean this up. computeRC should handle this check
-        if (!feature(FEATURE_SPEKTRUM))
+        if (!feature(FEATURE_SERIALRX))
             computeRC();
 
         // in 3D mode, we need to be able to disarm by switch at any time