Esp8266 Micropython Part 2 (#866)

* Add blog post from #664 * Update description
2025-07-18 14:56:53 +00:00 · 2016-08-31 07:02:01 +02:00 · 2016-08-31 07:02:01 +02:00 · aa4a4c68af
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+---
+layout: post
+title: "ESP8266 and MicroPython - Part 2"
+description: "Using MicroPython and MQTT on ESP8266 based devices and Home Assistant."
+date: 2016-08-31 06:17:25 +0200
+date_formatted: "August 31, 2016"
+author: Fabian Affolter
+comments: true
+categories: How-To MQTT ESP8266 Micropython
+og_image: /images/blog/2016-07-micropython/social.png
+---
+
+<img src='/images/blog/2016-07-micropython/micropython.png' style='clear: right; border:none; box-shadow: none; float: right; margin-bottom: 12px;' width='200' />
+So, part 1 of [ESP8266 and MicroPython](/blog/2016/07/28/esp8266-and-micropython-part1/) was pretty lame, right? Instead of getting information out of Home Assistant we are going a step forward and create our own sensor which is sending details about its state to a Home Assistant instance.
+
+<!--more-->
+
+Beside [HTTP POST](https://en.wikipedia.org/wiki/POST_(HTTP)) requests, MQTT is the quickest way (from the author's point of view) to publish information with DIY devices. 
+
+You have to make a decision: Do you want to pull or to poll? For slowly changing values like temperature it's perfectly fine to wait a couple of seconds to retrieve the value. If it's a motion detector the state change should be available instantly. This means the sensor must take initiative. 
+
+An example for pulling is [aREST](/components/sensor.arest/). This is a great way to work with the ESP8266 based units and the Ardunio IDE. 
+
+### {% linkable_title MQTT %}
+
+You can find a simple examples for publishing and subscribing with MQTT in the [MicroPython](https://github.com/micropython/micropython-lib) library overview in the section for [umqtt](https://github.com/micropython/micropython-lib/tree/master/umqtt.simple). 
+
+The example below is adopted from the work of [@davea](https://github.com/davea) as we don't want to re-invent the wheel. The configuration feature is crafty and simplyfies the code with the usage of a file called `/config.json` which stores the configuration details. The ESP8266 device will send the value of a pin every 5 seconds.
+
+
+```python
+import machine
+import time
+import ubinascii
+import webrepl
+
+from umqtt.simple import MQTTClient
+
+# These defaults are overwritten with the contents of /config.json by load_config()
+CONFIG = {
+    "broker": "192.168.1.19",
+    "sensor_pin": 0, 
+    "client_id": b"esp8266_" + ubinascii.hexlify(machine.unique_id()),
+    "topic": b"home",
+}
+
+client = None
+sensor_pin = None
+
+def setup_pins():
+    global sensor_pin
+    sensor_pin = machine.ADC(CONFIG['sensor_pin'])
+
+def load_config():
+    import ujson as json
+    try:
+        with open("/config.json") as f:
+            config = json.loads(f.read())
+    except (OSError, ValueError):
+        print("Couldn't load /config.json")
+        save_config()
+    else:
+        CONFIG.update(config)
+        print("Loaded config from /config.json")
+
+def save_config():
+    import ujson as json
+    try:
+        with open("/config.json", "w") as f:
+            f.write(json.dumps(CONFIG))
+    except OSError:
+        print("Couldn't save /config.json")
+
+def main():
+    client = MQTTClient(CONFIG['client_id'], CONFIG['broker'])
+    client.connect()
+    print("Connected to {}".format(CONFIG['broker']))
+    while True:
+        data = sensor_pin.read()
+        client.publish('{}/{}'.format(CONFIG['topic'],
+                                          CONFIG['client_id']),
+                                          bytes(str(data), 'utf-8'))
+        print('Sensor state: {}'.format(data))
+        time.sleep(5)
+
+if __name__ == '__main__':
+    load_config()
+    setup_pins()
+    main()
+```
+
+Subscribe to the topic `home/#` or create a [MQTT sensor](/components/sensor.mqtt/) to check if the sensor values are published.
+
+```bash
+$ mosquitto_sub -h 192.168.1.19 -v -t "home/#"
+```
+
+```yaml
+sensor:
+  - platform: mqtt
+    state_topic: "home/esp8266_[last part of the MAC address]"
+    name: "MicroPython"
+```
+
+[@davea](https://github.com/davea) created [sonoff-mqtt](https://github.com/davea/sonoff-mqtt). This code will work on ESP8622 based devices too and shows how to use a button to control a relay.
+