Creating A Custom NovAtel Style Log

The Lua string library can be used to parse NovAtel ASCII logs and create new custom logs. The example below shows how to do that. Note the following:

The string.find function is used to split the TIMEA log into its header and data.
The string.gmatch function is then used to split up the individual comma-separated data fields. The data fields are then stored into table, which can be used as required.
The string.format function is used to format a new log.

A tutorial on the Lua String Library can be found here: www.lua.org/pil/20.html.

The full script, as well as the required crc32.lua module is available in the Lua Dev Kit.

--******************************************************************************

-- Parse a string, looking for a TIMEA log

-- Inputs:

-- Buffer_ String containing input data

-- Returns:

-- nil if no TIMEA log is found

-- A table representing the data of a TIMEA log if a log is found

--******************************************************************************

function ParseTIMEA(Buffer_)

-- Search for a TIMEA log.

-- string.find returns the start and stop index as well as any strings that are "captured" within the parentheses

local FindTIMEAStart

local FindTIMEAStop

local TIMEAHeader

local TIMEAData

FindTIMEAStart,FindTIMEAStop, TIMEAHeader,TIMEAData

= Buffer_:find("#(TIMEA[^;]*;)([^%*]*%*).-\n")

if FindTIMEAStart ~= nil then

-- Found a TIMEA log

-- split the header into its elements

local HeaderIter = TIMEAHeader:gmatch("([^,]-)[,%;]")

HeaderData = {}

HeaderData['Message'] = HeaderIter()

HeaderData['Port'] = HeaderIter()

HeaderData['Sequence'] = HeaderIter()

HeaderData['IdleTime'] = HeaderIter()

HeaderData['TimeStatus'] = HeaderIter()

HeaderData['Week'] = HeaderIter()

HeaderData['Second'] = HeaderIter()

HeaderData['ReceiverStatus'] = HeaderIter()

HeaderData['Reserved'] = HeaderIter()

HeaderData['ReceiverSWVersion'] = HeaderIter()

-- Split the data into its elements

-- gmatch returns an iterator function that can be called successively to get

-- the next string matching the pattern.

local DataIter = TIMEAData:gmatch("([^,]-)[,%*]")

-- Create a table for the Time Data and assign the data fields into that table

TimeData = {}

TimeData['Header'] = HeaderData

TimeData['ClockStatus'] = DataIter()

TimeData['Offset'] = DataIter()

TimeData['OffsetStd'] = DataIter()

TimeData['UTCOffset'] = DataIter()

TimeData['UTCYear'] = DataIter()

TimeData['UTCMonth'] = DataIter()

TimeData['UTCDay'] = DataIter()

TimeData['UTCHour'] = DataIter()

TimeData['UTCMinute'] = DataIter()

TimeData['UTCMillisecond'] = DataIter()

TimeData['UTCStatus'] = DataIter()

return TimeData

end

-- NOTE: There is an implicit return of nil for Lua functions

-- that do not otherwise return a value

end

--******************************************************************************

-- Create a custom NovAtel-like log based on data from a TIMEA log that contains

-- the UTC Month

-- Inputs:

-- TimeData_ String containing input data

-- Returns:

-- Custom Log String

--******************************************************************************

local function CreateMonthLog(TimeData_,OutputPort_)

local HeaderData = TimeData_['Header']

local MonthTable = { 'January','February','March','April','May','June','July','August','September','October','November','December' }

-- Setup the Header and Data.

-- Leave out the leading # and trailing * as they are not included in the CRC

local CustomLog =

string.format("MONTHA,%s,%s,%s,%s,%s,%s,%s,%s,%s;%s",

OutputPort_, -- Note that the port is updated to the port where this log will be sent

HeaderData['Sequence'],

HeaderData['IdleTime'],

HeaderData['TimeStatus'],

HeaderData['Week'],

HeaderData['Second'],

HeaderData['ReceiverStatus'],

HeaderData['Reserved'],

HeaderData['ReceiverSWVersion'],

MonthTable[tonumber(TimeData['UTCMonth'])])

-- the crc32.lua script is included with the NovAtel Lua Dev Kit

local CRC = require("crc32").CalculateBlock(CustomLog,0)

-- Format together the leading #, the log data, the trailing * and calculated CRC.

return string.format("#%s*%08x",CustomLog,CRC)

end

--******************************************************************************

-- Request TIMEA logs on SCOM1, parse them and produce a new NovAtel-like custom log

-- Inputs:

-- arg[1] String representing the output port (e.g. 'COM1')

--******************************************************************************

local function main()

local OutputPort = arg[1]

if OutputPort == nil then

print("No Output Port Specified")

return

end

local SocketLib = require("socket")

local SocketSCOM1 = SocketLib.udp()

-- Setup the sockets

local TargetIP = "127.0.0.1"

assert(SocketSCOM1:setsockname("*",0))

assert(SocketSCOM1:setpeername(TargetIP,require("scom").GetSCOMPort(1)))

assert(SocketSCOM1:settimeout(3))

-- Request the TIMEA log on SCOM1

SocketSCOM1:send("LOG TIMEA ONTIME 1\r")

while true do

-- Wait for TIMEA Logs

local Buffer = SocketSCOM1:receive()

if Buffer == nil then

print("... timed out")

break

end

local TimeData = ParseTIMEA(Buffer)

if TimeData ~= nil then

-- Uncomment the lines below to dump out the parsed TIMEA data

-- for Key,Value in pairs(TimeData) do

-- if type(Value) == "table" then

-- print(string.format("%s:",Key))

-- for SubKey,SubValue in pairs(Value) do

-- print(string.format(" %s: \"%s\"",SubKey,SubValue))

-- end

-- else

-- print(string.format("%s: \"%s\"",Key,Value))

-- end

-- print("------------------------\n")

-- Format the new log

local MonthLog = CreateMonthLog(TimeData,OutputPort)

-- Send the log out the port

-- Note in firmware version OM7MR0500RN0000 the SEND command can only

-- send 100 bytes at once. That is sufficient for this example, but

-- in an actual use case the log should be sent out in 100 byte chunks.

SocketSCOM1:send(string.format('send %s \"%s\"\r',OutputPort,MonthLog))

end

--******************************************************************************

main()