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103 lines
4.1 KiB
Markdown
103 lines
4.1 KiB
Markdown
---
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title: "ESP8266 and MicroPython - Part 2"
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description: "Using MicroPython and MQTT on ESP8266 based devices and Home Assistant."
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date: 2016-08-31 06:17:25 +0200
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date_formatted: "August 31, 2016"
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author: Fabian Affolter
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categories: How-To MQTT ESP8266 Micropython
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og_image: /images/blog/2016-07-micropython/social.png
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---
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<img src='/images/blog/2016-07-micropython/micropython.png' style='clear: right; border:none; box-shadow: none; float: right; margin-bottom: 12px;' width='200' />
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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.
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<!--more-->
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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.
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You have to make a decision: Do you want to pull or to [poll](https://en.wikipedia.org/wiki/Polling_(computer_science)) the information for the sensor? 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 in Home Assistant or it could be missed. This means the sensor must take initiative and send the data to Home Assistant.
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An example for pulling is [aREST](/integrations/arest#sensor). This is a great way to work with the ESP8266 based units and the Ardunio IDE.
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## MQTT
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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/micropython/umqtt.simple).
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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.
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```python
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import machine
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import time
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import ubinascii
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import webrepl
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from umqtt.simple import MQTTClient
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# These defaults are overwritten with the contents of /config.json by load_config()
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CONFIG = {
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"broker": "192.168.1.19",
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"sensor_pin": 0,
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"client_id": b"esp8266_" + ubinascii.hexlify(machine.unique_id()),
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"topic": b"home",
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}
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client = None
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sensor_pin = None
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def setup_pins():
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global sensor_pin
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sensor_pin = machine.ADC(CONFIG['sensor_pin'])
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def load_config():
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import ujson as json
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try:
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with open("/config.json") as f:
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config = json.loads(f.read())
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except (OSError, ValueError):
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print("Couldn't load /config.json")
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save_config()
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else:
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CONFIG.update(config)
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print("Loaded config from /config.json")
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def save_config():
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import ujson as json
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try:
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with open("/config.json", "w") as f:
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f.write(json.dumps(CONFIG))
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except OSError:
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print("Couldn't save /config.json")
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def main():
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client = MQTTClient(CONFIG['client_id'], CONFIG['broker'])
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client.connect()
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print("Connected to {}".format(CONFIG['broker']))
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while True:
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data = sensor_pin.read()
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client.publish('{}/{}'.format(CONFIG['topic'],
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CONFIG['client_id']),
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bytes(str(data), 'utf-8'))
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print('Sensor state: {}'.format(data))
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time.sleep(5)
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if __name__ == '__main__':
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load_config()
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setup_pins()
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main()
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```
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Subscribe to the topic `home/#` or create a [MQTT sensor](/integrations/sensor.mqtt/) to check if the sensor values are published.
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```bash
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mosquitto_sub -h 192.168.1.19 -v -t "home/#"
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```
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```yaml
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sensor:
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- platform: mqtt
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state_topic: "home/esp8266_[last part of the MAC address]"
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name: "MicroPython"
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```
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[@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.
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