Water Level Sensor

This project contains the code for using an ultrasonic distance sensor to determine the water level in a tank.

An Arduino Uno reads from the sensor, sends the data to a 4-digit display, and uses an ESP8266 to log the data to a remote ThingsBoard instance hosted on Google Cloud Platform.

The ESP8266 is programmed to handle all the web traffic, receiving wake signal from the Uno and data via serial.

Hardware

1. Arduino Uno R3
2. WiFi ESP-01 (ESP8266) (with simple breakout board)
3. Ultrasonic Sensor AJ-SR04M
4. Display TM1637
5. Bi-directional Logic Level Controller

Gotchas

To program the ESP8266 using the Arduino Uno (this can be programmed but the one channel in my LLC broke, so I couldn't automate the GPI0 High/Low).

1. Make sure Uno Sketch is empty (select Uno board).
2. Select ESP8266 board.
3. Connect Rx to Rx, Tx to Tx.
4. Put ESP in Flash Mode
   1. ESP GPI0 -> GND
   2. ESP RST -> GND then 3.3V (just a quick tap)
   3. ESP GPI0 -> 3.3V (or float) (GPI0 must not be GND for Upload).
5. Upload sketch.

FatalException and IllegalInstruction

I had lots and lots of trouble with the ESP throwing all sorts of exceptions and stack traces, which I never fully nailed down. I believe it had to do with the breadboard connections and the iffy serial communication, also possibly power issues, although I would watch it work flawlessly for a few uploads and then just start crashing, and then fix itself and then crash again. I ended up moving stuff around on the breadboard, made sure the wires were fasted, erased the flash a number of times, and tried putting the original firmware on, and NodeCMU, all of which were unsuccessful. The last post on this page helped me get things back on track.

• erase flash -> esptool.py --chip ESP8266 --baud 115200 --port /dev/ttyACM0 erase_flash
• nodecmu -> esptool.py --chip ESP8266 --baud 115200 --port /dev/ttyACM0 write_flash -z --flash_mode dio --flash_freq 80m --flash_size 1MB 0x0 ~/Downloads/nodemcu-release-7-modules-2022-07-15-21-56-08-float.bin (or --flash_mode qio/--flash_mode dout)

WiFi fails.

I tried using the WiFiAutoSelector.h which did seem to work, but it coincided with the time I started getting all the crashes and FatalExceptions, so I reverted back to a simple hardcoded cycle through known WiFis. Not pretty, but does the job. Will make updating/changing the WiFi settings a mission, but I don't foresee that happening anytime soon, so we should be good.

Wiring