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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
+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/README.md b/README.md
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+# ESP8266 Lua/NodeMCU MQTT to UART bridge
+
+[esp8266-nodemcu-uart-bridge](https://finalrewind.org/projects/esp8266-nodemcu-uart-bridge/)
+provides an ESP8266 NodeMCU Lua application (`init.lua`) that mirrors
+incoming MQTT messages to the ESP8266's UART and can also transmit messages
+received by UART to an MQTT broker or to InfluxDB. This way, it can add simple
+MQTT/InfluxDB connectivity to devices that do not have a WiFi / ethernet
+connection.
+
+## Dependencies
+
+`init.lua` has been tested with Lua 5.1 on NodeMCU firmware 1.5.4.1(39cb9a32)
+(commit 81ec3665cb5fe68eb8596612485cc206b65659c9, integer build). This allows
+it to run on old ESP8266-01 boards with just 512kB of Flash. It requires the
+following modules.
+
+* http
+* mqtt
+* node
+* tmr
+* wifi
+
+## Usage
+
+### Startup
+
+Once connected, the ESP8266 will output the following lines on its TX line:
+
+* `WiFi:Rdy` *IP-address*
+* `MQTT:Rdy` *MQTT-prefix*
+
+The default MQTT prefix is `uart/esp8266_`*Chip-ID*, e.g.
+`uart/esp8266_82B45C`.  Additionally, the ESP8266 will publish a retained
+"online" message under *MQTT-prefix*/**state** and subscribe to
+*MQTT-prefix*/**in**.
+
+### MQTT to UART
+
+The ESP8266 prints each received *message* with an "RX:" prefix on its TX line,
+like so:
+
+`RX:`*message*
+
+### UART to MQTT
+
+When the ESP8266 receives **publish_mqtt**(*topic*, *payload*, *retain*) on its
+RX line, it will publish the specified payload under the specified topic.
+The *retain* flag defaults to false. For instance, the following input will
+publish "hello" under `uart/esp8266_`*Chip-ID*`/out`:
+
+`publish_mqtt(mqtt_prefix .. "/out", "hello")`
+
+If the message has been sent out successfully, it will reply with `MQTT:OK` or
+`> MQTT:OK`. Otherwise, it will reply with `MQTT:Err` or `> MQTT:Err`
+
+### Watchdog
+
+If none of the following four events happen for a time span of 90 seconds, the
+ESP8266 will reset itself, causing a re-connection to WiFi and MQTT server.
+
+* The ESP8266 receives a message via MQTT
+* The ESP8266 receives a **publish_mqtt** command via RX and the command
+  completes successfully
+* The ESP8266 receives a **publish_influx** command via RX and the command
+  completes successfully
+* The ESP8266 receiveds a **wdr()** command via RX.
+
+### Error Handling
+
+The following messages on the ESP8266 TX line indicate errors.
+Note that some errors can have several reasons.
+
+* `MQTT:Err` or `> MQTT:Err` – Failed to publish MQTT message (another message was still being
+  processed)
+* `MQTT:Err` or `> MQTT:Err` – Connection to MQTT broker has been lost
+* `WiFi:Err` or `> WiFi:Err` – Unable to establish WiFi connection
+* `WiFi:Err` or `> WiFi:Err` – WiFi connection has been lost
+* `Watchdog:Err` or `> Watchdog: Err` – watchdog timeout, the device will reset (see above)
+
+## Configuration
+
+To use this application, you need to create a **config.lua** file with WiFI and
+MQTT settings:
+
+```lua
+station_cfg = {ssid = "...", pwd = "..."}
+mqtt_host = "..."
+```
+
+To use InfluxDB, configure URL and (optional) header:
+
+```lua
+influx_url = "..."
+influx_header = "..."
+```
+
+## Resources
+
+Mirrors of this repository are maintained at the following locations:
+
+* [Chaosdorf](https://chaosdorf.de/git/derf/esp8266-nodemcu-uart-bridge)
+* [git.finalrewind.org](https://git.finalrewind.org/esp8266-nodemcu-uart-bridge/)
+* [GitHub](https://github.com/derf/esp8266-nodemcu-uart-bridge)
diff --git a/firmware/nodemcu-master-15-modules-2017-01-03-14-04-53-integer.bin b/firmware/nodemcu-master-15-modules-2017-01-03-14-04-53-integer.bin
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diff --git a/init.lua b/init.lua
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+publishing_mqtt = false
+publishing_http = false
+
+watchdog = tmr.create()
+chip_id = string.format("%06X", node.chipid())
+device_id = "esp8266_" .. chip_id
+mqtt_prefix = "uart/" .. device_id
+mqttclient = mqtt.Client(device_id, 120)
+
+dofile("config.lua")
+
+function wdr()
+	watchdog:stop()
+	watchdog:start()
+end
+
+function wd_err()
+	print("Watchdog:Err")
+	node.restart()
+end
+
+function mqtt_err(client)
+	print("MQTT:Err")
+end
+
+function wifi_err()
+	print("WiFi:Err " .. wifi.sta.status())
+end
+
+function setup_client()
+	print("MQTT:Rdy " .. mqtt_prefix)
+	publishing_mqtt = true
+	mqttclient:publish(mqtt_prefix .. "/state", "online", 0, 1, function(client)
+		client:subscribe(mqtt_prefix .. "/in", 0)
+		publishing_mqtt = false
+	end)
+end
+
+function connect_mqtt()
+	print("")
+	print("WiFi:Rdy " .. wifi.sta.getip())
+	mqttclient:on("connect", setup_client)
+	mqttclient:on("offline", mqtt_err)
+	--mqttclient:on("connfail", mqtt_err)
+	mqttclient:on("message", print_mqtt)
+	mqttclient:lwt(mqtt_prefix .. "/state", "offline", 0, 1)
+	mqttclient:connect(mqtt_host)
+end
+
+function connect_wifi()
+	wifi.eventmon.register(wifi.eventmon.STA_GOT_IP, connect_mqtt)
+	wifi.eventmon.register(wifi.eventmon.STA_DHCP_TIMEOUT, wifi_err)
+	wifi.eventmon.register(wifi.eventmon.STA_DISCONNECTED, wifi_err)
+	wifi.setmode(wifi.STATION)
+	wifi.sta.config(station_cfg)
+	wifi.sta.connect()
+end
+
+function print_mqtt(client, topic, message)
+	print("RX:" .. message)
+	wdr()
+	collectgarbage()
+end
+
+function publish_mqtt(topic, payload, retain)
+	if publishing_mqtt then
+		print("MQTT:Err")
+	else
+		publishing_mqtt = true
+		mqttclient:publish(topic, payload, 0, retain or 0, function(client)
+			publishing_mqtt = false
+			print("MQTT:OK")
+			wdr()
+			collectgarbage()
+		end)
+	end
+end
+
+function publish_influx(payload)
+	if publishing_http then
+		print("Influx:Err")
+	else
+		publishing_http = true
+		http.post(influx_url, influx_header, payload, function(code, data)
+			publishing_http = false
+			print("Influx:OK")
+			wdr()
+			collectgarbage()
+		end)
+	end
+end
+
+watchdog:register(90 * 1000, tmr.ALARM_SEMI, wd_err)
+watchdog:start()
+
+connect_wifi()