GPS.lua

--[[#############################################################################
Telemetry Widget script for Taranis x7 
Copyright (C) by mosch   
License GPLv2: http://www.gnu.org/licenses/gpl-2.0.html       

"GPS last known postions v1.1"  
 
Desrciption:

stores GPS coordinates every second into /SCRIPTS/TELEMETRY/GPSpositions.txt and displays the last 4 GPS positions 
and GPS sattelite count on the telemetry screen. In case that telemetry is not available anymore (crash, power loss etc.) 
the screen won't be updated but still shows the last 4 postions. If 50 postions are stored, the log will be reset and 
starts at 0.

if the sattelite count always shows 0 or no value change the following line in the script:

	from:
	gpssatId = getTelemetryId("Tmp2")
	to:
	gpssatId = getTelemetryId("Sats")

################################################################################]]

log_filename = "/SCRIPTS/TELEMETRY/GPSpositions.txt"

local gpsValue = 0
local gpsLAT = 0
local gpsLON = 0
local gpsSATS = 0
local wait_time = 100
local wait_time_read = 100
local old_time_read = 0
local old_time_write = 0
local coordinates = {}  
local coordinates_tmp = {} 
local update = true
local string_gmatch = string.gmatch
local now = 0
local ctr = 0

coordinates[1] = "0"
coordinates[2] = "0"
coordinates[3] = "0"
coordinates[4] = "0"

local function rnd(v,d)
	if d then
		return math.floor((v*10^d)+0.5)/(10^d)
	else
		return math.floor(v+0.5)
	end
end

local function write_log()
	now = getTime()    
    if old_time_write + wait_time < now then
						
		if string.len(gpsValue) <= 8 then
			gpsLAT = "not available"
			gpsLON = "not available"		
		else			
			local f = io.open(log_filename, "a")        
				io.write(f, gpsValue ,"\r\n")			
			io.close(f)				
		end		
		old_time_write = now
    end
end


local function read_log()
	ctr = 0	
	now = getTime()    
		
		if old_time_read + wait_time_read < now then

			local f2 = io.open(log_filename, "r")
				buffer = io.read(f2, 2048)
			io.close(f2)

			for line in string_gmatch(buffer, "([^\n]+)\n") do					
				ctr = ctr + 1
				coordinates_tmp[ctr] = line
			end			

			if ctr > 49 then
				local f2 = io.open(log_filename, "w")
				io.close(f2)		
			end
			
			if ctr == 1 then			
				coordinates[1] = "1: " .. coordinates_tmp[ctr]
				coordinates[2] = "2: 0" 
				coordinates[3] = "3: 0" 
				coordinates[4] = "4: 0" 
			end			
			if ctr == 2 then			
				coordinates[1] = "1: " .. coordinates_tmp[ctr-1]
				coordinates[2] = "2: " .. coordinates_tmp[ctr]
				coordinates[3] = "3: 0" 
				coordinates[4] = "4: 0" 
			end	

			if ctr == 3 then			
				coordinates[1] = "1: " .. coordinates_tmp[ctr-2]
				coordinates[2] = "2: " .. coordinates_tmp[ctr-1]
				coordinates[3] = "3: " .. coordinates_tmp[ctr]
				coordinates[4] = "4: 0" 
			end
			
			if ctr > 3 then						
				coordinates[1] = ctr-3 .. ": " .. coordinates_tmp[ctr-3]
				coordinates[2] = ctr-2 .. ": " .. coordinates_tmp[ctr-2]	
				coordinates[3] = ctr-1 .. ": " .. coordinates_tmp[ctr-1]
				coordinates[4] = ctr .. ": " .. coordinates_tmp[ctr]				
			end	
					
			old_time_read = now
		end
	
end

local function getTelemetryId(name)    
	field = getFieldInfo(name)
	if field then
		return field.id
	else
		return-1
	end
end

local function init()  
	gpsId = getTelemetryId("GPS")
		
	gpssatId = getTelemetryId("Tmp2")
	--gpssatId = getTelemetryId("Sats")]]
end

local function background()	
	
	gpsLatLon = getValue(gpsId)	
	gpsSATS = getValue(gpssatId)
	
	if (type(gpsLatLon) == "table") then 
	
		gpsValue = rnd(gpsLatLon["lat"],6) .. ", " .. rnd(gpsLatLon["lon"],6)
		gpsLAT = rnd(gpsLatLon["lat"],6)
		gpsLON = rnd(gpsLatLon["lon"],6)		
		update = true					
	else    	
		gpsValue = ""			
	end		
	
	if string.len(gpsValue) > 8 then	
		write_log()		
		update = true
	else
		gpsValue = " no gps data available"
		update = false
	end 
	
	read_log()
	
	
	if string.len(gpsSATS) > 2 then
		gpsSATS = string.sub (gpsSATS, 3,6)
		gpsSATS = "Sat:" .. gpsSATS
	end	
	
			
end
 
local function run(event)  
	lcd.clear()  
	background() 
			
	lcd.drawText(2,2,"Last GPS positions",SMLSIZE)
	lcd.drawLine(0,10, 128, 10, SOLID, FORCE)
	
	lcd.drawText(2,14, coordinates[1],SMLSIZE)
	lcd.drawText(2,26, coordinates[2],SMLSIZE)
	lcd.drawText(2,38, coordinates[3],SMLSIZE)
	lcd.drawText(2,50, coordinates[4],SMLSIZE)
	
	
	
	if update == true then
		lcd.drawText(100,2, gpsSATS, SMLSIZE + INVERS + BLINK)
				
	elseif update == false then
		lcd.drawText(100,2,"Sat:--", SMLSIZE) 
	end
	
end
 
return {init=init, run=run, background=background}