init.lua

-- load credentials, 'SSID' and 'PASSWORD' declared and initialize in there
local config = require("config")

function startup()
    if file.open("init.lua") == nil then
        print("init.lua deleted or renamed")
    else
        print("Running")
        file.close("init.lua")
        -- the actual application is stored in 'application.lua'
        -- dofile("app.lua")
        
        countdown = 3
        tmr.alarm(0, 1000, 1, function()
            print(countdown)
            countdown = countdown-1
            if countdown<1 then
                tmr.stop(0)
                countdown = nil
                local s,err
                s,err = pcall(function() dofile("app.lua") end)
                if not s then print(err) end
            end
        end)
    end
end

-- Define WiFi station event callbacks 
wifi_connect_event = function(T) 
  print("Connection to AP("..T.SSID..") established!")
  print("Waiting for IP address...")
  if disconnect_ct ~= nil then disconnect_ct = nil end  
end

wifi_got_ip_event = function(T) 
  -- Note: Having an IP address does not mean there is internet access!
  -- Internet connectivity can be determined with net.dns.resolve().    
  print("Wifi connection is ready! IP address is: "..T.IP)
  print("Startup will resume momentarily, you have 3 seconds to abort.")
  print("Waiting...") 
  tmr.create():alarm(3000, tmr.ALARM_SINGLE, startup)
end

wifi_disconnect_event = function(T)
  if T.reason == wifi.eventmon.reason.ASSOC_LEAVE then 
    --the station has disassociated from a previously connected AP
    return 
  end
  -- total_tries: how many times the station will attempt to connect to the AP. Should consider AP reboot duration.
  local total_tries = 75
  print("\nWiFi connection to AP("..T.SSID..") has failed!")

  --There are many possible disconnect reasons, the following iterates through 
  --the list and returns the string corresponding to the disconnect reason.
  for key,val in pairs(wifi.eventmon.reason) do
    if val == T.reason then
      print("Disconnect reason: "..val.."("..key..")")
      break
    end
  end

  if disconnect_ct == nil then 
    disconnect_ct = 1 
  else
    disconnect_ct = disconnect_ct + 1 
  end
  if disconnect_ct < total_tries then 
    print("Retrying connection...(attempt "..(disconnect_ct+1).." of "..total_tries..")")
  else
    wifi.sta.disconnect()
    print("Aborting connection to AP!")
    disconnect_ct = nil  
  end
end

-- Register WiFi Station event callbacks
wifi.eventmon.register(wifi.eventmon.STA_CONNECTED, wifi_connect_event)
wifi.eventmon.register(wifi.eventmon.STA_GOT_IP, wifi_got_ip_event)
wifi.eventmon.register(wifi.eventmon.STA_DISCONNECTED, wifi_disconnect_event)

print("Connecting to WiFi access point...")
wifi.setmode(wifi.STATION)
wifi.sta.config({ssid=config.WIFI_SSID, pwd=config.WIFI_PASSWD, save=true})
-- wifi.sta.connect() not necessary because config() uses auto-connect=true by default