iotdistance

IOT Distance Sensor for ESP8266 (ESP201) with OTA and WiFi

Introduction

This project is an Internet-of-Things (IoT) distance sensor that can be used to measure the proximity and distance of objects. Using the System on a Chip (SoC) ESP3266 process, which has a native 802.11 interface (WiFi), it provides distance information via built-in http server, and JSON formatted responses.

One application is for garage door status sensing, another use is as a parking distance sensor. It can be built on a single board, and packaged in a small enclosure. A Nagios check script was written, so that distance changes can be logged and alerted via a Nagios monitoring server.

The devices mates the an Ultrasonic distance sensor (cheap and plentiful HC-SRC04) and ESP8266 module (ESP201) for an Internet-of-Things (IoT) distance sensor that is easy to build and use. It uses the Arduino IDE environment, along with the Arduino ESP8266 board manager extension, for development.

The ESP201 module requires an external resistor, button, and switch for performing firmware loading, and reset. The circuit schematic provides a re-usable design for the ESP201 module, as well as dual power supply, and 5v to 3.3v level shifting for the Ultrasonic module.

The device software also includes Over-The-Air (OTA) firmware updates. Install the php script (tools/esp8266 directory) to an Apache server, and copy the desired .ino.bin file, and update the script to include the device MAC address and firmware name. You can then use the '/distance/updatefirmware' api query to load the new firmware and reboot automatically.

Features

• distance sensor (1cm to 4 meters)
• http query/response with JSON responses (ReST format)
• WiFi interface and automatic association
• helper scripts for command line queries and Nagios integration
• OTA updates feature - remotely update firmware (http server using php script)

Protocol

Query: http://<ip address>[:80]/distance/info

Response:

{ "info": 1,
   "ipaddr": "192.168.20.10", 
   "ssid": "mygateway", 
   "rssi": -81, 
   "mac": "5c:6a:e:7f:cf:55", 
   "version": "1.1g", 
   "sensor": "distance"
}

Query: http://<ip address>[:80]/distance/get

Response:

{  "get": 1,
   "distance": 304,
   "mac": "5c:6a:e:7f:cf:5c",
   "version": "1.1g", 
   "sensor": "distance"
}

Query: http://<ip address>[:80]/distance/updatefirmware

Response:

{  "update": 1,
   "ipaddr": "192.168.20.10", 
   "mac": "5c:6a:e:7f:cf:5c",
   "version": "1.0g", 
   "sensor": "distance"
}

Invalid Response (unknown query):

{  "invalid": 1,
   "request": "GET /distance/invalid", 
   "mac": "5c:6a:e:7f:cf:5c",
   "version": "1.0g", 
   "sensor": "distance"
}

Installation

The .ino sketch should be loaded and compiled for the ESP8266.

The script needs to be updated to provide the SSID and password for your WiFi network.

The firmware loading procedure:

• Connect a FTDI usb adapter to the 6 pin header on the board.
• Set the switch to program mode
• press the reset button
• click the upload button on the Arduino IDE
• the firmware should upload to the device (blinkenlights)
• when its done, set the switch to run mode
• press the reset button to start the new firmware.

The IoT device should then associate with the network, and get an ip address. The device also responds to ping messages (ICMP).

Setting up the OTA server

An optional Over-The-Air (OTA) server can be setup to allow remote firmware upgrades. Note that this version of the OTA server does not have any security or authentication, so use in a production environment is not recommended.

To setup the OTA server:

• Setup an Apache Web Server with PHP 7.0+ (<fwhost>.
• create a firmware directory on the server:
  mkdir /var/www/html/esp8266
• copy the firmware-latest.php and device.ini files
  cp tools/esp8266/firmware-latest.php /var/www/html/esp8266
cp tools/esp8266/device.ini /var/www/html/esp8266
  test the script by running (using Linux GET command) :
  GET http://<fwhost>/esp8266/firmware-latest.php
  correct response:
  only for ESP8266 updater!
• edit the device.ini file and add your device mac address and firmware .bin file name.
• cp the new firmware bin file to firmware directory:
  Note: the .bin file is in your build/ directory. cp iotdistance.ino.bin /var/www/html/esp8266

To use the OTA server:
Once the device is loaded with the initial firmware, further upgrades can be performed remotely by doing:

• call the upgradefirmware query on the device:
  http://<device ip addr/distance/upgradefirmware
  You should get a upgrade response (see above) and the device should disconnect, load the new firmware, and reboot.
  Wait a bit (30 seconds), and run a info query to verify.

References

• ESP201 First Impressions review of the module
• Programming ESP201 with Arduino how to set up programming
• ESP201 Cheat Sheet one page cheat sheet
• Setting up ESP8266 Programmin on Arduino SparkFun's overview
• Nagios Monitoring