HTTP control, relay control and OTA/HTTP firmware updates using an ESP8266 for just $11

The ESP8266 came out a few years ago and people were really excited about its capabilities. I stayed away from it because there were no tools, no decent peripheral libraries, and a questionable supply chain.  Fast forward to today and the situation has dramatically changed. Software development is now supported in the Arduino IDE, the PlatformIO development platform and by NodeMCU.

Microcenter stocks several different ESP8266 boards by AdaFruit, Link Sprite, and others. They had the LinkSprite with mounting holes, a relay and onboard voltage regulation for sale at $11 so I bought one. The board is smaller than a playing card but larger than many other ESP8266 SBCs. I like the Link Sprite because it is case ready and has soldered-in headers for peripherals. The Link Sprite LinkNode R1 is essentially compatible with the Wemos D1 retired from a programming point of view.

A video version of this blog is available on YouTube.

A Simple Program for Relay Control

  • Automatic Wi-fi portal for auto-configuration on new networks.
  • A built-in web server
  • Bonjour style DNS so clients can find the server by name
  • Unique hostname for each device
  • Web form-based relay control.
  • Direct URL (GET) relay control
  • Web-based firmware updates with authentication
  • Unique password for each device.
  • Direct connect OTA firmware updates with authentication
  • Remote Reset
  • No real security.
The document to the right shows the web page home screen with both relay control and administrative functionality.

Software Components

The diagram to the right shows the major software components The source resides in this GitHub repository. It consists of the following major components: 
  1. Network and Wi-Fi
  2. An auto-configuring Wi-Fi access point
  3. Web Server
  4. Firmware update services
  5. Relay control web form and handlers
The Network, DNS, Web Server, OTA update feature, and web OTA update features are all publicly available Arduino libraries.  I blended the available services, created the web form, and created a form and HTTP request relay control code.

Programming Requirements 

This program was built with the Arduino IDE and ESP8266 support package 2.3.0. I had a little trouble with 2.4. See the README.md on GitHub for more details.

Initial programming must be done with a USB-to-serial cable (3 Volt). I used both a Prolific 2303 clone cable and an old UARTs Bee adapter board.  Many sites have instructions on how to use the Arduino IDE.  Link Sprite's wiki page also has links.  

Network configuration is done upon restart after a programming cycle. The ESP8266 program brings up an Access Point portal that can be sued to select a network and enter a password. This program remembers that connection information. The program remembers network connection information across program versions.

Follow-on programming can be done Over the Air (OTA) without the serial cable once the device has joined a network. You can submit firmware binaries via web form or use the espota.py python scripts to do the work. See the README.md for details.

OTA updates are significantly faster than those done over USB.


Hardware

Built on Link Spring LinkNode Rx that emulates the WeMos D1 (retired)
  • ESP-87266EX
  • 5V DC power jack
  • 1 Digital/IO Relay
  • 6 Digital I/O pins
  • 1 Analog Input pin
The Arduino pinout and ESP8266 pin mapping can be found in pins_arduino.h on github The Arduino pin naming convention doesn't make sense in this context. It is simpler to just refer directly to the ESP8266 pin number itself. The following table shows both representations.
GPIOFcnAlt FcnArduino pinR4 Relay
GPIO 04SDA?D4
GPIO 05SCL?D3
GPIO 12HMISOD6S4
GPIO 13HMOSIRXD2D7S5
GPIO 14HSCLKD5S3
GPIO 15HCSTXD2D10
GPIO 16R1 relayD2S2
GPIO2 is tied to the on-module ESP8266 Blue LED

Comments

This board is pretty amazing for the price. The tooling is good. Probably my only gripe is that the software can get pretty big lengthening the development cycle. 

I did blow the TX/RX lines of one of mine before I got OTA working. That board won't be getting new firmware anytime soon.




Created 2018 03 14
Grammer fixes 2022 11 16

Comments

Post a Comment

Popular posts from this blog

Installing the RNDIS driver on Windows 11 to use USB Raspberry Pi as network attached

Image
I do a lot of my development and configuration via ssh into my Raspberry Pi Zero over the RNDIS connection. Some models of the Raspberry PIs can be configured with  gadget drivers  that let the Raspberry pi emulate different devices when plugged into computers via USB. My favorite gadget  is the network profile that makes a Raspberry Pi look like an RNDIS-attached network device.  All types of network services travel over an RNDIS device without knowing it is a USB hardware connection. A Raspberry Pi shows up as a Remote NDIS (RNDIS) device when you plug the Pi into a PC or Mac via a USB cable. The gadget  in the Windows Device Manager picture shows this RNDIS Gadget connectivity between a Windows machine and a Raspberry Pi. The Problem Windows 11 and Windows 10 no longer auto-installs the RNDIS driver that makes magic happen. Windows recognizes that the Raspberry Pi is some type of generic USB COM device. Manually running W indows Update  or  Upd...
Read more

Understanding your WSL2 RAM and swap - Changing the default 50%-25%

Image
The Windows Subsystem for Linux operates as a virtual machine that can dynamically grow the amount of RAM to a maximum set at startup time.  Microsoft sets a default maximum RAM available to 50% of the physical memory and a swap-space that is 1/4 of the maximum WSL RAM.  You can scale those numbers up or down to allocate more or less RAM to the Linux instance. The first drawing shows the default WSL memory and swap space sizing. The images below show a developer machine that is running a dev environment in WSL2 and Docker Desktop.  Docker Desktop has two of its own WSL modules that need to be accounted for.  You can see that the memory would actually be oversubscribed, 3 x 50% if every VM used its maximum memory.  The actual amount of memory used is significantly smaller allowing every piece to fit. Click to Enlarge The second drawing shows the memory allocation on my 64GB laptop. WSL Linux defaul...
Read more

Almost PaaS Document Parsing with Tika and AWS Elastic Beanstalk

Image
The Apache Tika project provides a  library capable of parsing and extracting data and meta data from over 1000 file types.  Tika is available as a single jar file that can be included inside applications or as a deployable jar file that runs Tika as a standalone service. This blog describes deploying the Tika jar as an auto-scale service in Amazon AWS Elastic Beanstalk.  I selected Elastic Beanstalk because it supports jar based deployments without any real Infrastructure configuration. Elastic Beanstalk auto-scale should take care of scaling up and down for for the number of requests you get. Tika parses documents and extracts their text completely in memory. Tika was deployed for this blog using EC2 t2.micro instances available in the AWS free tier. t2.micro VMs are 1GB which means that you are restricted in document complexity and size. You would size your instances appropriately for your largest documents.   Preconditions An AWS account. AWS ac...
Read more