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diff --git a/.gitignore b/.gitignore
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+config.lua
diff --git a/.reuse/dep5 b/.reuse/dep5
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+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+
+Files: init.lua ccs811.lua
+Copyright: 2024 Birte Kristina Friesel
+License: BSD-2-Clause
+
+Files: README.md .gitignore
+Copyright: 2024 Birte Kristina Friesel
+License: CC0-1.0
diff --git a/LICENSES/BSD-2-Clause.txt b/LICENSES/BSD-2-Clause.txt
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+++ b/LICENSES/BSD-2-Clause.txt
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+Copyright (c) <year> <owner> 
+
+Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/LICENSES/CC0-1.0.txt b/LICENSES/CC0-1.0.txt
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--- /dev/null
+++ b/LICENSES/CC0-1.0.txt
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+Creative Commons Legal Code
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diff --git a/README.md b/README.md
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+# ESP8266 Lua/NodeMCU module for CCS811 VOC sensors
+
+[esp8266-nodemcu-ccS811](https://finalrewind.org/projects/esp8266-nodemcu-ccs811/)
+provides an ESP8266 NodeMCU Lua module (`ccs811.lua`) as well as MQTT /
+HomeAssistant / InfluxDB gateway application example (`init.lua`) for
+**CCS811** volatile organic compounds (VOC) sensors connected via I²C.  The
+application example assumes that an **HDC1080** sensor for temperature and
+humidity compensation is available as well.
+
+## Dependencies
+
+ccs811.lua has been tested with Lua 5.1 on NodeMCU firmware 3.0.1 (Release
+202112300746, float build). It requires the following modules.
+
+* bit
+* i2c
+
+Most practical applications (such as the example in init.lua) also need the
+following modules.
+
+* hdc1080
+* gpio
+* mqtt
+* node
+* tmr
+* wifi
+
+## Setup
+
+Connect the CCS811 sensor (or CCS811/HDC1080 combo board) to your
+ESP8266/NodeMCU board as follows.
+
+* CCS811 GND → ESP8266/NodeMCU GND
+* CCS811 VCC → ESP8266/NodeMCU 3V3
+* CCS811 SDA → NodeMCU D1 (ESP8266 GPIO5)
+* CCS811 SCL → NodeMCU D2 (ESP8266 GPIO4)
+
+If you use different pins for SCL and SDA, you need to adjust the i2c.setup
+call in the examples provided in this repository to reflect those changes. Keep
+in mind that some ESP8266 pins must have well-defined logic levels at boot time
+and may therefore be unsuitable for CCS811 connection.
+
+## Usage
+
+Copy **ccs811.lua** to your NodeMCU board and set it up as follows.
+
+```lua
+ccs811 = require("ccs811")
+i2c.setup(0, 1, 2, i2c.SLOW)
+ccs811.start()
+
+-- can be called with up to 1 Hz
+function some_timer_callback()
+	if ccs811.read() then
+		-- ccs811.eco2   : equivalent CO₂ (estimated from tvoc, unreliable) [ppm]
+		-- ccs811.tvoc   : Total Volatile Organic Compounds [ppb]
+		-- ccs811.status : Status Register; see manual
+		-- ccs811.error  : Error Register; see manual. error == 0 indicates that everything is alright.
+		-- optionally, if HDC1080 is available:
+		local t, h = hdc1080.read()
+		ccs811.setEnv(h, t)
+	end
+end
+```
+
+The sensor performs an air quality measurement every second.
+
+## Application Example
+
+**init.lua** is an example application with HomeAssistant integration.
+To use it, you need to create a **config.lua** file with WiFI and MQTT settings:
+
+```lua
+station_cfg = {ssid = "...", pwd = "..."}
+mqtt_host = "..."
+```
+
+Optionally, it can also publish readings to InfluxDB.
+To do so, configure URL and attribute:
+
+```lua
+influx_url = "..."
+influx_attr = "..."
+```
+
+Readings will be published as `ccs811[influx_attr] eco2_ppm=%d,tvoc_ppb=%d,status=%d,error=%d`.
+Unless `influx_attr = ''`, it must start with a comma, e.g. `influx_attr = ',device=' .. device_id`.
+
+## Images
+
+![](https://finalrewind.org/projects/esp8266-nodemcu-ccs811/media/hass.png)
diff --git a/ccs811.lua b/ccs811.lua
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--- /dev/null
+++ b/ccs811.lua
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+local ccs811 = {}
+local device_address = 0x5a
+
+ccs811.mode = nil
+
+function ccs811.start()
+	local ret = true
+	i2c.start(0)
+	if not i2c.address(0, device_address, i2c.TRANSMITTER) then
+		ret = false
+	end
+	i2c.write(0, 0xf4)
+	i2c.stop(0)
+	return ret
+end
+
+function ccs811.setMode(mode)
+	local ret = true
+	i2c.start(0)
+	if not i2c.address(0, device_address, i2c.TRANSMITTER) then
+		ret = false
+	end
+	i2c.write(0, 0x01, bit.lshift(mode, 4))
+	i2c.stop(0)
+	ccs811.mode = mode
+	return ret
+end
+
+function ccs811.setEnv(humi, temp)
+	local ret = true
+	i2c.start(0)
+	if not i2c.address(0, device_address, i2c.TRANSMITTER) then
+		ret = false
+	end
+	i2c.write(0, 0x05, math.floor(humi) * 2, 0, (math.floor(temp) + 25) * 2, 0)
+	i2c.stop(0)
+	return ret
+end
+
+function ccs811.read()
+	local ret = true
+	if ccs811.mode == nil then
+		ccs811.setMode(1)
+		return
+	end
+	i2c.start(0)
+	if not i2c.address(0, device_address, i2c.TRANSMITTER) then
+		ret = false
+	end
+	i2c.write(0, 0x02)
+	i2c.start(0)
+	if not i2c.address(0, device_address, i2c.RECEIVER) then
+		ret = false
+	end
+	local data = i2c.read(0, 6)
+	i2c.stop(0)
+
+	ccs811.eco2 = bit.lshift(string.byte(data, 1), 8) + string.byte(data, 2)
+	ccs811.tvoc = bit.lshift(string.byte(data, 3), 8) + string.byte(data, 4)
+	ccs811.status = string.byte(data, 5)
+	ccs811.err_id = string.byte(data, 6)
+
+	return ret
+end
+
+return ccs811
diff --git a/init.lua b/init.lua
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+++ b/init.lua
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+publishing_mqtt = false
+publishing_http = false
+
+watchdog = tmr.create()
+push_timer = tmr.create()
+chip_id = string.format("%06X", node.chipid())
+device_id = "esp8266_" .. chip_id
+mqtt_prefix = "sensor/" .. device_id
+mqttclient = mqtt.Client(device_id, 120)
+
+dofile("config.lua")
+
+print("CCS811 " .. chip_id)
+
+ledpin = 4
+gpio.mode(ledpin, gpio.OUTPUT)
+gpio.write(ledpin, 0)
+
+ccs811 = require("ccs811")
+i2c.setup(0, 1, 2, i2c.SLOW)
+
+function log_restart()
+	print("Network error " .. wifi.sta.status())
+end
+
+function setup_client()
+	print("Connected")
+	gpio.write(ledpin, 1)
+	publishing_mqtt = true
+	mqttclient:publish(mqtt_prefix .. "/state", "online", 0, 1, function(client)
+		publishing_mqtt = false
+		hdc1080.setup()
+		ccs811.start()
+		push_timer:start()
+	end)
+end
+
+function connect_mqtt()
+	print("IP address: " .. wifi.sta.getip())
+	print("Connecting to MQTT " .. mqtt_host)
+	mqttclient:on("connect", hass_register)
+	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 push_data()
+	local t, h = hdc1080.read()
+	local json_str = string.format('{"temperature_degc": %.1f, "humidity_relpercent": %.1f', t, h)
+	local influx_str = string.format("temperature_degc=%.1f,humidity_relpercent=%.1f", t, h)
+	if ccs811.read() then
+		json_str = json_str .. string.format(', "eco2_ppm": %d, "tvoc_ppb": %d, "status": "0x%02x", "error": "0x%02x"', ccs811.eco2, ccs811.tvoc, ccs811.status, ccs811.err_id)
+		influx_str = influx_str .. string.format(',eco2_ppm=%d,tvoc_ppb=%d,status=%d,error=%d', ccs811.eco2, ccs811.tvoc, ccs811.status, ccs811.err_id)
+		ccs811.setEnv(h, t)
+	else
+		json_str = json_str .. ', "status": "Initializing", "error": "0x00"'
+	end
+	json_str = json_str .. string.format(', "rssi_dbm": %d}', wifi.sta.getrssi())
+	if not publishing_mqtt then
+		publishing_mqtt = true
+		watchdog:start(true)
+		gpio.write(ledpin, 0)
+		mqttclient:publish(mqtt_prefix .. "/data", json_str, 0, 0, function(client)
+			publishing_mqtt = false
+			if influx_url and influx_attr then
+				publish_influx(influx_str)
+			else
+				gpio.write(ledpin, 1)
+				collectgarbage()
+			end
+		end)
+	end
+end
+
+function publish_influx(payload)
+	if not publishing_http then
+		publishing_http = true
+		http.post(influx_url, influx_header, "ccs811" .. influx_attr .. " " .. payload, function(code, data)
+			publishing_http = false
+			gpio.write(ledpin, 1)
+			collectgarbage()
+		end)
+	end
+end
+
+function hass_register()
+	local hass_device = string.format('{"connections":[["mac","%s"]],"identifiers":["%s"],"model":"ESP8266 + HDC1080 + CCS811","name":"CCS811 %s","manufacturer":"derf"}', wifi.sta.getmac(), device_id, chip_id)
+	local hass_entity_base = string.format('"device":%s,"state_topic":"%s/data","expire_after":120', hass_device, mqtt_prefix)
+	local hass_temp = string.format('{%s,"name":"Temperature","object_id":"%s_temp","unique_id":"%s_temp","device_class":"temperature","unit_of_measurement":"°c","value_template":"{{value_json.temperature_degc}}","entity_category":"diagnostic"}', hass_entity_base, device_id, device_id)
+	local hass_humi = string.format('{%s,"name":"Humidity","object_id":"%s_humidity","unique_id":"%s_humidity","device_class":"humidity","unit_of_measurement":"%%","value_template":"{{value_json.humidity_relpercent}}","entity_category":"diagnostic"}', hass_entity_base, device_id, device_id)
+	--local hass_eco2 = string.format('{%s,"name":"eCO₂","object_id":"%s_eco2","unique_id":"%s_eco2","device_class":"carbon_dioxide","unit_of_measurement":"ppm","value_template":"{{value_json.eco2_ppm}}"}', hass_entity_base, device_id, device_id)
+	local hass_voc = string.format('{%s,"name":"VOC","object_id":"%s_voc","unique_id":"%s_voc","unit_of_measurement":"ppb","icon":"mdi:air-filter","value_template":"{{value_json.tvoc_ppb}}"}', hass_entity_base, device_id, device_id)
+	local hass_status = string.format('{%s,"name":"Status","object_id":"%s_status","unique_id":"%s_status","icon":"mdi:information","value_template":"{{value_json.status}}","entity_category":"diagnostic"}', hass_entity_base, device_id, device_id)
+	local hass_error = string.format('{%s,"name":"Error","object_id":"%s_error","unique_id":"%s_error","icon":"mdi:alert-circle","value_template":"{{value_json.error}}","entity_category":"diagnostic"}', hass_entity_base, device_id, device_id)
+	local hass_rssi = string.format('{%s,"name":"RSSI","object_id":"%s_rssi","unique_id":"%s_rssi","device_class":"signal_strength","unit_of_measurement":"dBm","value_template":"{{value_json.rssi_dbm}}","entity_category":"diagnostic"}', hass_entity_base, device_id, device_id)
+
+	mqttclient:publish("homeassistant/sensor/" .. device_id .. "/temperature/config", hass_temp, 0, 1, function(client)
+		mqttclient:publish("homeassistant/sensor/" .. device_id .. "/humidity/config", hass_humi, 0, 1, function(client)
+			--mqttclient:publish("homeassistant/sensor/" .. device_id .. "/eco2/config", hass_eco2, 0, 1, function(client)
+				mqttclient:publish("homeassistant/sensor/" .. device_id .. "/tvoc/config", hass_voc, 0, 1, function(client)
+					mqttclient:publish("homeassistant/sensor/" .. device_id .. "/status/config", hass_status, 0, 1, function(client)
+						mqttclient:publish("homeassistant/sensor/" .. device_id .. "/error/config", hass_error, 0, 1, function(client)
+							mqttclient:publish("homeassistant/sensor/" .. device_id .. "/rssi/config", hass_rssi, 0, 1, function(client)
+								collectgarbage()
+								setup_client()
+							end)
+						end)
+					end)
+				end)
+			--end)
+		end)
+	end)
+end
+
+watchdog:register(180 * 1000, tmr.ALARM_SEMI, node.restart)
+push_timer:register(10 * 1000, tmr.ALARM_AUTO, push_data)
+watchdog:start()
+
+connect_wifi()