Ambient Sensor with ESP and Micropython

Overview

This repository contains Micropython code for the ESP with a DHT11 shield. What it does is tranform the small MCU into a small ambient sensor, that reads Temperature and Humidity and publishes the date to a local MQTT Broker on my home network.

To parse, store and display the data, i also setup Mosquitto, Node Red, InfluxDB, and built a few Grafana Dashboards, since i used a couple of this small sensors around the house, for bedroom and living room

I used a small ESP01-S, which is an inexpensive ESP with a attached onto a small PCB. The code makes use of the deepsleep available on the MCU, in order to reduce the battery so it can run for a long time, but since it only has very few Pins available on the plug, to use the deepsleep properly i had to solder a small wire connecting GPIO 16 (available on the chip) to the RST Pin, which is available on the plug.

Because i used a very small version of the ESP, there are a few tricks that are listed on this readme, that are specific to this MCU/Package.

Code explanation

Altough the functionality is quite basic, the code has passed through a few iterations until all bugs were eliminated. Pretty much the usual connection problems, like stalled MQTT, unfinished wifi connection.

The steps the application performs are:

connect to wifi network
connect to mqtt broker
acquire data from sensors
publish sensor data via mqtt
publish network status via mqtt
deep sleep/sleep for N seconds

Hardware Requirements

ESP01-S
USB Programmer
Thin wire for the deepsleep shunt
a piece of wire to shunt other pins
ESP DHT11 Shield

Software Requirements

Ampy
ESPtool

Usefull commands

send a file to a board running micropython

ampy -p /dev/ttyUSB0 -b 115200 put path/to/file

enter REPL over serial

screen /dev/ttyUSB0 115200

basic esptool command

esptool.py --chip esp8266 --port /dev/ttyUSB1 ?????

clear flash memory

esptool.py --chip esp8266 --port /dev/ttyUSB0 erase_flash

upload new firmware

esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash --flash_size=detect 0 esp826-???????

FAQ

How to setup the code ?

clean the MCU flash memory, 2) flash the MCU with the new micropython firmware, 3) send over the project files (WiFi and MQTT already configured)

How the deepsleep works ? after the chip enters the deepsleep mode, it disables everything except a clock, which continues to tick for a finite number of seconds, configured by the user. When the sleep time expires, the chip emits an interrupt on Pin 16, so being it connected to RST, it makes the chip reset and execute it's code again.
How to flash the ESP01-S ? add a small piece of wire to shunt the Pin IO0 to GND before putting the MCU onto the USB Programmer

image

How to enable deepsleep ? solder a piece of thin wire between GPIO 16 and the RST Pin, to allow the chip to wake from the deepsleep.