MicroPython-WaterSensor

This simple project uses a NodeMCU - Aka Espressif ESP8266 - and cheap chinese water flow sensor YF-B1 and MicroPython.

My sensor supports multiple sensors, uses Wifi and MQTT to publish status updates.

Install MicroPython

I will quickly cover the steps for ESP8266. For more information, refer to the official documentation at https://docs.micropython.org/en/latest/esp8266/tutorial/intro.html.

Install ESPTOOL

esptool is used to flash the NodeMCU/ESP8266 with the MicroPython firmware. For this project, no need to rebuild MicroPython.

pip install --user esptool

Erase the NodeMCU flash

First, the flash needs to be erased (on my Mac, the usb-serial port is /dev/cu.SLAB_USBtoUART):

esptool.py --port /dev/cu.SLAB_USBtoUART erase_flash

Download the Firmware from MicroPython website.

http://micropython.org/download

Flash the firmware

esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash --flash_size=detect -fm dio 0 esp8266-20170108-v1.8.7.bin

At this stage, you should have a working MicroPython ESP8266 board. You can attach to the Python shell using screen for example:

/dev/ttyUSB0 115200

Upload the software

The software is composed of 2 files, boot.py and main.py, similarly as Arduino sketch composed of setup() and loop() functions.

To upload the software, you need ampy.

pip install adafruit-ampy

Using ampy, you can interact with the board. Keep in mind that as any serial port, it cannot be accessed by multiple software at the same time (eg. screen).

As explained in the documentation, MicroPython formats the flash as FAT and hosts software.

To list files on the FAT partition:

ampy --port /dev/cu.SLAB_USBtoUART --baud 115200 ls

Use my program

To use my program, you will need to upload main.py and config.json.

{
    "wifi": {
        "SSID" : "MyIoTSSID",
        "PSK" : "SuperSecretKey"
    },
    "mqtt": {
        "broker" : "mqttbroker",
        "client" : "wtr-sens",
        "prefix" : "wtr/",
        "t_status" : "status",
        "t_cons" : "consumption"
    },
    "pulsesPerLitre" : 2500,
    "sensors": [
        { "name": "hot", "pin": 14 },
        { "name": "cold", "pin": 15 }
    ],
    "statusLed": 16
}

Upload the two files:

ampy --port /dev/cu.SLAB_USBtoUART --baud 115200 put main.py
ampy --port /dev/cu.SLAB_USBtoUART --baud 115200 put config.json

The sensor regularly saves its state to the flash to be able to resume on power failure.

If you want to monitor the sensor, use screen. To soft reboot and reload the software, you can issue a CTRL+D.