init.lua

-- Config
SSID = "ssid_name"
PASS = "ssid_pass"

MQTT_TEMP_TOPIC = "/sensors/study/temperature"
MQTT_HOST       = "server IP"
MQTT_PORT       = 1883
MQTT_CLIENT_ID  = "esp2866_study"
MQTT_USER       = ""
MQTT_PASS       = ""
MQTT_RECONNECT  = 1
MQTT_SECURE     = 0

-- TMP102 settings
TMP102_ID       = 0
TMP102_SDA      = 6
TMP102_SCL      = 7
-- Allow correcting temperatures by subtracting this
TMP102_BIAS     = 0 

-- Number of seconds to wait for a wifi connection before restarting
MAX_RETRIES     = 20

-- Measurement interval (ms)
TEMP_INTERVAL   = 10000

function wifi_connect(ssid, pass)
    wifi.setmode(wifi.STATION)
    wifi.sta.config(ssid, pass)

    local wifi_count = 0

    tmr.alarm(0, 1000, 1, function()
        wifi_status =  wifi.sta.status()
        if wifi_status ~= 5 then
            wifi_count = wifi_count + 1

            if wifi_count >= MAX_RETRIES then
                print("Failed to connect. Restarting")
                node.restart()
            end

            print("Not yet connected.")
        else
            ip, mask, gateway = wifi.sta.getip()
            print("Connected")
            print("IP address: ", ip)
            print("Netmask:    ", mask)
            print("Gateway:    ", gateway)
	    tmr.stop(0)
	    mqtt_setup()
        end
    end) -- end of alarm function
end

function mqtt_setup()
    local mqtt_connection = 0

    -- Connect to the MQTT broker
    mqtt = mqtt.Client(MQTT_CLIENT_ID, 120, MQTT_USER, MQTT_PASS)
    mqtt:connect(MQTT_HOST, MQTT_PORT, MQTT_SECURE, MQTT_RECONNECT)

    mqtt:on("connect", function(client)

        print("Connected to MQTT server")
        mqtt_connection = 1

	-- Load the TMP102 module
	tmp102=dofile("tmp102.lua")
        tmp102.begin(TMP102_ID, TMP102_SDA, TMP102_SCL)

        tmr.alarm(0, TEMP_INTERVAL, 1, function()
            temp=tmp102.celcius() - TMP102_BIAS
            print("Read temperature from TMP102: ", temp)
            mqtt:publish(MQTT_TEMP_TOPIC, temp, 0, 0)
        end)
    end)

    -- TODO: reconnection logic if auto-reconnect fails
    mqtt:on("offline", function(client)
        print("Lost connection to MQTT server")
        mqtt_connection = 0
    end)
end

function main()

    -- Connect to the network
    wifi_connect(SSID, PASS)

end

-- Run the main function
main()