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+config.lua
diff --git a/README.md b/README.md
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+# ESP8266 Lua/NodeMCU module for Vindriktning PM1006 particle monitor
+
+This repository contains a Lua module (`pm1006.lua`) as well as ESP8266/NodeMCU
+MQTT gateway application example (`init.lua`) for the **PM1006** particulate
+matter (PM2.5) sensor found in IKEA Vindriktning.
+
+## Dependencies
+
+pm1006.lua has been tested with Lua 5.1 on NodeMCU firmware 3.0.1 (Release
+202112300746, integer build). Most practical applications (such as the example
+in init.lua) require the following modules.
+
+* gpio
+* mqtt
+* node
+* softuart
+* tmr
+* uart
+* wifi
+
+## Setup
+
+Connect the PM1006 sensor to your ESP8266/NodeMCU board as [documented by Hypfer](https://github.com/Hypfer/esp8266-vindriktning-particle-sensor).
+
+If you use a different UART pin, you need to adjust the softuart.setup call in
+the examples provided in this repository to reflect that change. Keep in mind
+that some ESP8266 pins must have well-defined logic levels at boot time and may
+therefore be unsuitable for PM1006 connection.
+
+## Usage
+
+Copy **pm1006.lua** to your NodeMCU board and set it up as follows.
+
+```lua
+pm1006 = require("pm1006")
+port = softuart.setup(9600, nil, 2)
+port:on("data", 20, uart_callback)
+
+function uart_callback(data)
+	local pm2_5 = pm1006.parse_frame(data)
+	if pm25i ~= nil then
+		-- pm2_5 contains PM2.5 value in µg/m³
+	else
+		-- invalid frame header or checksum
+	end
+end
+```
+
+See **init.lua** for an example. To use it, you need to create a **config.lua** file with WiFI and MQTT settings:
+
+```lua
+station_cfg.ssid = "..."
+station_cfg.pwd = "..."
+mqtt_host = "..."
+```
diff --git a/init.lua b/init.lua
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+station_cfg = {}
+dofile("config.lua")
+
+delayed_restart = tmr.create()
+chipid = node.chipid()
+mqtt_prefix = "sensor/esp8266_" .. chipid
+mqttclient = mqtt.Client("esp8266_" .. chipid, 120)
+
+print("ESP8266 " .. chipid)
+
+ledpin = 4
+gpio.mode(ledpin, gpio.OUTPUT)
+gpio.write(ledpin, 0)
+
+pm1006 = require("pm1006")
+
+function log_restart()
+	print("Network error " .. wifi.sta.status() .. ". Restarting in 20 seconds.")
+	delayed_restart:start()
+end
+
+function setup_client()
+	print("Connected")
+	gpio.write(ledpin, 1)
+	publishing = true
+	mqttclient:publish(mqtt_prefix .. "/state", "online", 0, 1, function(client)
+		publishing = false
+	end)
+	port = softuart.setup(9600, nil, 2)
+	port:on("data", 20, uart_callback)
+end
+
+function connect_mqtt()
+	print("IP address: " .. wifi.sta.getip())
+	print("Connecting to MQTT " .. mqtt_host)
+	delayed_restart:stop()
+	mqttclient:on("connect", setup_client)
+	mqttclient:on("offline", log_restart)
+	mqttclient:lwt(mqtt_prefix .. "/state", "offline", 0, 1)
+	mqttclient:connect(mqtt_host)
+end
+
+function connect_wifi()
+	print("WiFi MAC: " .. wifi.sta.getmac())
+	print("Connecting to ESSID " .. station_cfg.ssid)
+	wifi.eventmon.register(wifi.eventmon.STA_GOT_IP, connect_mqtt)
+	wifi.eventmon.register(wifi.eventmon.STA_DHCP_TIMEOUT, log_restart)
+	wifi.eventmon.register(wifi.eventmon.STA_DISCONNECTED, log_restart)
+	wifi.setmode(wifi.STATION)
+	wifi.sta.config(station_cfg)
+	wifi.sta.connect()
+end
+
+function uart_callback(data)
+	local pm2_5 = pm1006.parse_frame(data)
+	if pm2_5 == nil then
+		print("Invalid PM1006 frame")
+		return
+	else
+		local json_str = string.format('{"pm25_ugm3": %d, "rssi_dbm": %d}', pm2_5, wifi.sta.getrssi())
+		if not publishing then
+			publishing = true
+			gpio.write(ledpin, 0)
+			mqttclient:publish(mqtt_prefix .. "/data", json_str, 0, 0, function(client)
+				publishing = false
+				gpio.write(ledpin, 1)
+				collectgarbage()
+			end)
+		end
+	end
+end
+
+delayed_restart:register(20 * 1000, tmr.ALARM_SINGLE, node.restart)
+
+connect_wifi()
diff --git a/pm1006.lua b/pm1006.lua
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+local pm1006 = {}
+
+function pm1006.parse_frame(data)
+	if string.byte(data, 1) ~= 0x16 or string.byte(data, 2) ~= 0x11 or string.byte(data, 3) ~= 0x0b then
+		-- invalid header
+		return nil
+	end
+	local checksum = 0
+	for i = 1, 20 do
+		checksum = (checksum + string.byte(data, i)) % 256
+	end
+	if checksum ~= 0 then
+		-- invalid checksum
+		return nil
+	end
+	local pm2_5 = string.byte(data, 6) * 256 + string.byte(data, 7)
+	return pm2_5
+end
+
+return pm1006