AP_Scripting: add ahrs-print-variances example

libraries/AP_Scripting/examples/ahrs-print-variances.lua

@@ -0,0 +1,17 @@
+-- This script displays the ahrs variances at 1hz
+-- get_variances provides the innovations normalised using the innovation variance
+-- a value of 0 indicates perfect consistency between the measurement and the EKF solution
+-- a value of 1 is the maximum inconsistency that will be accepted by the filter
+-- nil is returned for all arguments if variances are not available
+
+function update() -- this is the loop which periodically runs)
+  vel_variance, pos_variance, height_variance, mag_variance, airspeed_variance = ahrs:get_variances()
+  if vel_variance then
+    gcs:send_text(0, string.format("Variances Pos:%.1f Vel:%.1f Hgt:%.1f Mag:%.1f", pos_variance, vel_variance, height_variance, mag_variance:length()))
+  else
+    gcs:send_text(0, string.format("Failed to retrieve variances"))
+  end
+  return update, 1000 -- reschedules the loop
+end
+
+return update() -- run immediately before starting to reschedule