SITL: fudge zero-length to 1cm for Wasp and NoopLoop drivers

both ArduPilot drivers consider 0 to be invalid, so you don't end up with any readings at all if you just send through 0 all the time.

Fudge 0cm to 1cm for the simulated data for these drivers

Author: peterbarker

libraries/SITL/SIM_RF_NoopLoop.cpp

@@ -22,6 +22,12 @@ using namespace SITL;
 
 uint32_t RF_Nooploop::packet_for_alt(uint16_t alt_cm, uint8_t *buffer, uint8_t buflen)
 {
+    // the NoopLoop driver considers a value of zero invalid and won't
+    // consider it a reading, so you end up with no readings at all
+    // from the driver.  Fudge it here:
+    if (alt_cm == 0) {
+        alt_cm = 1;
+    }
 
     int32_t alt_scaled = 2560*alt_cm;
     buffer[0] = 0x57;

libraries/SITL/SIM_RF_Wasp.cpp

@@ -113,5 +113,11 @@ void RF_Wasp::update(float range)
 
 uint32_t RF_Wasp::packet_for_alt(uint16_t alt_cm, uint8_t *buffer, uint8_t buflen)
 {
+    // the Wasp driver does not consider 0 a valid reading, so you end
+    // up getting 0 samples back if you send exactly zero all the
+    // time.  So munge it a little bit:
+    if (alt_cm == 0) {
+        alt_cm = 1;
+    }
     return snprintf((char*)buffer, buflen, "%f\n", alt_cm*0.01f);
 }