Joshua's Docs - ESP Modules (ESP32, ESP8266) by Expressif - Notes


What & Link Type
ESP8266 Community Wiki Wiki / Reference
ElectroDragon ESP Wikis Wiki / Reference
ESP8266 Community Forums Forums
Espressif Github Github Repos
Espressif ESP32 ESP-IDF Programming Guide
- Source Code: github
Mono Software: IoT with ESP8266 - Part 1: Basics
- Good intro to basics & options
Intro Guide
tttapa: Beginner's Guide to the ESP8266
- Github source
- Example sketches

ESP Board Pinouts

Flashing via USB

This is a great guide on flashing a ESP8266. The key things are:

  • 3.3v power supply
  • 3.3v RX and TX (either buy a programmer that supports it, or use voltage dividers)
  • Pull-up and pull-down specific pins, to set in "flash" mode

Hint: If you are getting gibberish on terminal after flashing new code, make sure you change the "flash" pin so that the device is out of flash mode, and restart. For example, for the ESP8266, you keep GPIO-0 (pin 4, flash) low for flash mode, but after you flash, you need to pull it up to high, to enter normal operation mode.

ESP OTA Updates

One of the major advantages to using a Wifi board over just a standard MCU is the ability to deliver OTA updates, as an alternative to flashing new code over a physical USB connection.

Most ESP guides for OTA recommend using ArduinoOTA, which even comes as a built-in example sketch with the ESP8266 add-on for the Arduino IDE.

You can find full documentation and instructions for the 8266 here. Most of it should also apply to the ESP32.

Few notes:

  • Think about where you want to put the OTA handler
    • If you want it to constantly listen for updates, you need to call the OTA handler every time, in the main loop()
    • You could use a physical button or switch to put it into a listen loop, to cut down on security risks from OTA udpates
  • You need to pay attention to chip memory (aka flash storage)
    • Since an OTA update requires the board to temporarily store the new binary, as well as the existing running code, you need to have memory equal to 2x the sketch size.
    • The OTA library itself will add a lot to your sketch size
      • Based on rough estimate, a sketch with nothing but the library works out to about 235 kB
      • On an older ESP8266 (v ESP01) with 512 kB of flash, this might mean that only 21 kB of storage is left for new code --> (512 - (235 * 2)) / 2 = 21.
        • Newer boards have more memory, which is good, since this is basically unusable with 512 kB.
        • You can also manually solder on new flash

You could also use a platform for ESP that supports OTA updates natively, such as Blynk or Espruino.

Support for Other Languages and Platforms

Aside from using Arduino / C++ code, you can also get other platforms to run on many ESP boards. For example:

Markdown Source Last Updated:
Mon May 25 2020 15:53:09 GMT+0000 (Coordinated Universal Time)
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Wed May 13 2020 18:09:32 GMT+0000 (Coordinated Universal Time)
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