AP_Scripting: add battery-resistance-checking example

libraries/AP_Scripting/examples/battery_internal_resistance_check.lua

@@ -0,0 +1,35 @@
+--[[
+ script implementing pre-arm check that internal resistance is sensible
+--]]
+
+local MAX_RESISTANCE = 0.03  -- Ohms
+
+local auth_id = assert(arming:get_aux_auth_id())
+
+local warning_last_sent_ms = uint32_t() -- time we last sent a warning message to the user
+warning_interval_ms = 10000
+
+function update()
+   local num_batts = battery:num_instances()
+   local ok = true
+   for i=0,num_batts do
+      local resistance = battery:get_resistance(i)
+      failed = resistance > MAX_RESISTANCE
+      if failed then
+         msg = string.format("Batt[%u] high internal resistance %.5f Ohms", i+1, resistance)
+         if millis() - warning_last_sent_ms > warning_interval_ms then
+            gcs:send_text(0, msg)
+            warning_last_sent_ms = millis()
+         end
+         arming:set_aux_auth_failed(auth_id, msg)
+         ok = false
+      end
+   end
+
+   if ok then
+      arming:set_aux_auth_passed(auth_id)
+   end
+   return update, 500
+end
+
+return update()