Shepherding electrons

Many ventures into the world of the ESP8266 chip and making Internet of Things devices would do worse than to start with the NodeMCU ESP-12E board.  I started my journey with the powerful but stripped back ESP-01S board - useful for projects such my IR-Egg and cat litter tray Twitter bot where space is an a premium, and very few GPIOs are required.  However I have recently got my hands on some NodeMCU ESP-12E boards and I'm enjoying the relative abundance of broken out pins, the builtin USB with 5V --> 3.3V conversion and programming over the USB.  So far I have used the ESP-12E boards in a couple of small projects, namely as a SPIFFs HTTP file server and as the reciprocal HTTP client . The board has a whopping 4 Mb of flash memory available, and an embarrassment of pins - I feel spoilt!

This is a brief guide to getting started with the Pro Micro Arduino Board (Atmega32U4) - not to be confused with the Pro Mini (which utilises the Atmega328P)!  Note that the Pro Micro board comes in two flavours/flavors - 5V @ 16 MHz and 3.3V @ 8 MHz, so make sure you know which you have before getting started.  It should be indicated on the bottom silkscreen of the bottom, or you could take a voltmeter and measure VCC against GND - it will be either 5V or 3.3V.

I recently blogged about how to setup an ESP8266 as a file server , in particular using SPIFFs to store the files.  But how can we retrieve HTML and general files from a web server?  In this post I'll demonstrate some code to make a request for a file from a server, then save the results on the SPIFFS on the ESP8266 client.  In terms of implementation, this works very well on a NodeMCU ESP-12E board.  I've also tried it on a ESP-01S board - there is a technical issue writing to SPIFFs within a program on some of the latest versions of this board.  There is a fix however, discussed at the end of this post.

How to setup an ESP8266 board as a server using SPIFFs This how-to guide describes using an ESP8266 chip to setup a server to do what servers do... serve files!  If you want to know how to retrieve files from a web server, see my post on using the ESP8266 as a HTTP client .  Although HTML and other files can be contained within the program itself ("sketch" in the Arduino parlance), it is inconvenient, especially if you want to deposit images on the ESP-board, or change your files in and out easily.  The solution is use to SPIFFs, a file system that uses the on-board SPI flash chip, which can be written directly from your computer (and read and written from programmatically within your sketch too).  The amount of memory will vary depending upon the board in question.