AP_Scripting: example to test ESC slew limit

can be used to calculate equivalent cutoff frequency

libraries/AP_Scripting/examples/ESC_slew_rate.lua

@@ -0,0 +1,54 @@
+--[[
+   run an ESC with a sinisoidal demand, with settable limits and frequency
+--]]
+
+local PARAM_TABLE_KEY = 136
+local PARAM_TABLE_PREFIX = "ETEST_"
+
+-- add a parameter and bind it to a variable
+function bind_add_param(name, idx, default_value)
+   assert(param:add_param(PARAM_TABLE_KEY, idx, name, default_value), string.format('could not add param %s', name))
+   return Parameter(PARAM_TABLE_PREFIX .. name)
+end
+
+-- setup script specific parameters
+assert(param:add_table(PARAM_TABLE_KEY, PARAM_TABLE_PREFIX, 10), 'could not add param table')
+
+local ETEST_CHAN      = bind_add_param('CHAN',          1, 0)
+local ETEST_PCT       = bind_add_param('PCT',           2, 100)
+local ETEST_PWM_MIN   = bind_add_param('PWM_MIN',       3, 1000)
+local ETEST_PWM_MAX   = bind_add_param('PWM_MAX',       4, 2000)
+local ETEST_FREQ      = bind_add_param('FREQ',          5, 1)
+local ETEST_WTYPE     = bind_add_param('WTYPE',         6, 0)
+
+-- local WTYPE_SIN = 0
+local WTYPE_SQUARE = 1
+
+function update()
+   local chan = ETEST_CHAN:get()
+   local freq = ETEST_FREQ:get()
+   if chan > 0 and freq > 0 then
+      local t = 0.001 * millis():tofloat()
+      local pi = 3.1415
+      local out_sin = math.sin(pi * t * freq * 2.0)
+      if ETEST_WTYPE:get() == WTYPE_SQUARE then
+         if out_sin > 0 then
+            out_sin = 1
+         else
+            out_sin = -1
+         end
+      end
+      local output = out_sin * ETEST_PCT:get() * 0.01
+      local pwm_min = ETEST_PWM_MIN:get()
+      local pwm_max = ETEST_PWM_MAX:get()
+      local pwm_mid = 0.5*(pwm_min+pwm_max)
+      local pwm = math.floor(pwm_mid + (pwm_max-pwm_mid) * output)
+      SRV_Channels:set_output_pwm_chan_timeout(chan-1, pwm, 100)
+      logger.write('ESLW', 'PWM,Freq', 'If', pwm, freq)
+      gcs:send_named_float('PWN',pwm)
+      gcs:send_named_float('FREQ',freq)
+   end
+   return update, 5 -- 200Hz
+end
+
+return update()