AP_Scripting: add rover-motor-driver example script

libraries/AP_Scripting/examples/rover-motor-driver.lua

@@ -0,0 +1,40 @@
+-- Rover motor driver for an Ackerman style vehicle (i.e. the frame has separate throttle and steering controls)
+--
+-- The following parameters should be set:
+--     SERVO1_FUNCTION = 94 (Script 1) 
+--     SERVO3_FUNCTION = 96 (Script 3)
+-- 
+-- The Frame's steering control should be connected to the autopilot's output1, throttle control to output3
+--
+-- CAUTION: This script only works for Rover
+-- This script retrieves the high level controller outputs that have been sent to the regular motor driver
+-- and then outputs them to the "Script 1" and "Script 3" outputs.  This does not add any real value beyond
+-- serving as an example of how lua scripts can be used to implement a custom motor driver 
+
+local K_SCRIPTING1 = 94 -- for steering control
+local K_SCRIPTING3 = 96 -- for throttle control
+local CONTROL_OUTPUT_THROTTLE = 3
+local CONTROL_OUTPUT_YAW = 4
+
+function update()
+  if not arming:is_armed() then
+    -- if not armed move steering and throttle to mid
+    SRV_Channels:set_output_norm(K_SCRIPTING1, 0)
+    SRV_Channels:set_output_norm(K_SCRIPTING3, 0)
+  else
+    -- retrieve high level steering and throttle control outputs from vehicle in -1 to +1 range
+    local steering = vehicle:get_control_output(CONTROL_OUTPUT_YAW)
+    local throttle = vehicle:get_control_output(CONTROL_OUTPUT_THROTTLE)
+    if (steering and throttle) then
+      if throttle < 0 then
+          steering = -steering
+      end
+      SRV_Channels:set_output_norm(K_SCRIPTING1, steering)
+      SRV_Channels:set_output_norm(K_SCRIPTING3, throttle)
+    end
+  end
+  return update, 10 -- run at 100hz
+end
+
+gcs:send_text(6, "rover-motor-driver.lua is running")
+return update()