-- 23.07.23/AH Learjet 35A FMS Synchronize "Digital Transponder" to P3D internal transponder
--
--	Flysimware Learjet 35A FMS Expansion Pack delivers a new "Digital Transponder" that synchronizes in a one-way fashion
--	the P3D internal transponder. This leads to a conflict with Pilot2ATC's "Copilot sets Squawk" option (overwriting the latter)
--	
--	This script starts by FSUIPC.ini [Auto] or [Auto.<profile>] Section, it could be started manually by FSUIPC button definition.
--		[Profile.Flysimware_Learjet35A_FMS]
--		1=Learjet 35A FMS N548PA
--		[Auto.Flysimware_Learjet35A_FMS]
--		1=LUA Lear35A_SyncXPDR
 
--	The Script's main procedure starts the sync function every 10.000 ms (or another value in variable cycletime)
--
--  The function LearSyncXpndr reads Digital Transponders LVARs and, if not existing, terminates itself (no Lear FMS aircraft)
--	The P3D internal transponder Squawk (2 bytes BCD coded at offset 0x0354) is divided into its nibbles (halfbytes)
--	They have to be combined digit by digit to a decimal number to compare (BCD x01200 = decimal 4608 <> decimal 1200)
--	If the Squawks are different, the Digital Transponder Squawk is set according to P3D internal Squawk.
--
--	It's a compromise:
--  On one site, manual setting of Digital Transponder is possible:
--  even if P3D internal transponder changes, there's a 10 seconds gap until the function runs again
--	On the other site if a tool like Pilot2ATC sets the P3D internal transponder and there's no focus in VC on the Digital Transponder
--	(knobs not activated by clicking on them), this script sets Digital Transponder accordingly after max. 10 seconds.

--
-- Sync function, called by main entry's event.timer every 10 seconds
--
function LearSyncXpndr(CurrentTime)
-- Get "Digital Transponder" Squawk Code
  DIGSQ1=ipc.readLvar("L:Digit1")
  DIGSQ2=ipc.readLvar("L:Digit2")
  DIGSQ3=ipc.readLvar("L:Digit3")
  DIGSQ4=ipc.readLvar("L:Digit4")
-- Check if "L:Digit..." LVARs were returned, if not: no Lear FMS - end timer procedure
  if DIGSQ1 == nil or DIGSQ2 == nil or DIGSQ3 == nil or DIGSQ4 == nil then
    ipc.display("LUA only for Flysimware Learjet 35A with FMS (L:Digit... undefined)")
	ipc.sleep(2000)
	ipc.exit()
  end
-- Combine Digital Transponder Squawk digits to decimal number
  DIGSQ=(DIGSQ1 * 1000) + (DIGSQ2 * 100) + (DIGSQ3 * 10) + DIGSQ4
-- Get P3D BCD-coded Squawk Code and extract nibbles (halfbytes)
-- we need them to build a decimal compare number and to set Digital Transponder if not equal
  XPNDR=ipc.readUW(0x0354)
  XPNDR1=logic.Shr(XPNDR,12)		-- get first nibble by shift right 12 bits
  XPNDR1=logic.And(XPNDR1,15)		-- and leave only rightmost four bits
  XPNDR2=logic.Shr(XPNDR,8)		-- get second nibble by shift right 8 bits
  XPNDR2=logic.And(XPNDR2,15)		-- and leave only rightmost four bits
  XPNDR3=logic.Shr(XPNDR,4)		-- get third nibble by shift right 4 bits
  XPNDR3=logic.And(XPNDR3,15)		-- and leave only rightmost four bits
  XPNDR4=logic.And(XPNDR,15)		-- get fourth nibble: leave only rightmost four bits
-- Combine P3D internal transponder digits to decimal number
  XPNDRDEC=(XPNDR1 * 1000) + (XPNDR2 * 100) + (XPNDR3 * 10) + XPNDR4
-- If Digital Transponder Squawk and P3D-internal Squawk are not equal: set "Digital Transponder"
  if DIGSQ ~= XPNDRDEC then
-- Set Digital Transponder Squawk to P3D Squawk 
    ipc.WriteLvar("L:Digit1", XPNDR1)
    ipc.WriteLvar("L:Digit2", XPNDR2)
    ipc.WriteLvar("L:Digit3", XPNDR3)
    ipc.WriteLvar("L:Digit4", XPNDR4)
  end

-- just for debugging: show nibbles in hex  
--  XPNDR1X=string.format("%x", XPNDR1)
--  XPNDR2X=string.format("%x", XPNDR2)
--  XPNDR3X=string.format("%x", XPNDR3)
--  XPNDR4X=string.format("%x", XPNDR4)
--  ipc.display("P3D XPD: " .. XPNDR1 .. "-" .. XPNDR2 .. "-" .. XPNDR3 .. "-" .. XPNDR4 .. ".") 
--  ipc.sleep(1000)
--  XPNDRX=string.format("%x", XPNDR)
--  ipc.display("P3D XPX: " .. XPNDR1X .. "-" .. XPNDR2X .. "-" .. XPNDR3X .. "-" .. XPNDR4X .. ".") 
--  ipc.sleep(1000)
--  ipc.display("P3D XP: " .. XPNDRX .. " (BCD !) DigXP: " .. DIGSQ)

end

--
-- Main Entry, called by FSUIPC.ini LUA entry in Section "[Auto]" or "[Auto.<profilename>]"
--
cycletime=10000
-- Display in P3D before starting cyclic function to prevent msg removal by function's own msgs
ipc.display("Starting Lear 35A Digital Transponder sync every " .. cycletime .. "ms")
ipc.sleep(8000)
ipc.display("")	-- clear display
-- Now start cyclic function for XPDR Sync
event.timer(cycletime, "LearSyncXpndr")
--