ESP8266

What's an ESP8266

Cheap microcontroller board that you can find online for <Rs 300/- (~3.5 USD) and is fully programmable.

Introduction

Got this from a hobby shop online and wanted to try writing some low-level code for it. The whole Arduino IDE and process seemed super unintuitive (abstracts away all the learning). So I decided to try writing a toolchain (using FreeRTOS) and some modules for it manually.

Why this board makes more sense for learning (compared to let's say an ESP32):

• Single-core CPU means you need to control the event loop manually for async operations
• No onboard ROM (only flash storage) means you need to be careful with data management
• No onboard crypto engine means you need to learn how the security features work and implement them yourself :)
• Still getting full control over bootloader/flash storage for a fraction of the price

Getting started

Prerequisites

1. An ESP8266 board
2. Computer/laptop as the host machine (I'm using WSL on Windows)
3. Micro-USB to USB-A/C cable to connect it to your computer

Completed Modules

1. hello-world - simple hello world on serial console and GPIO pin manipulation
2. dht-22 - control and read data from a DHT-22 Temperature and Humidity sensor
3. shell - interactive shell with extensible command template, command history, completion and more

Running the hello-world module code

1. Install python3, uv, binutils, curl, wget, gcc, git, linux-libc-dev, make on your host machine using your package manager.
2. Clone this repository

git clone git@github.com:vishnuvardhan-kumar/esp8266.git
cd esp8266/

3. If you have direnv installed and configured, it should kick in and set up some config automatically. I highly recommend using this! If you decide not to, open the .envrc file and add the configuration to your environment manually.
4. Set the setup.sh file executable and run it to download the toolchain and SDK.

chmod +x setup.sh
./setup.sh

5. Spin up the uv virtual environment and sync packages.

uv sync
# (activate the virtualenv if not using direnv)

6. Navigate into the directory and run make menuconfig

cd hello-world/
make menuconfig

7. If the project make linkage worked correctly, it should now show a TUI with configuration options. I have set sane defaults for almost everything, ensure to change the Serial Flasher Config to the device name for your USB serial port (Eg: COMx on Windows, /dev/ttyUSBSn on Linux)

8. Save and quit the visual interface with Esc-Esc.

9. Now you have a bunch of make targets to play with the project:

make app           # compile only the application
make all           # compile application + libraries
make flash         # compile all, flash the executable to the target serial device
make monitor       # open up a serial monitor for I/O

10. You should be able to get up and running by using!

make flash monitor

11. Post the flashing sequence - you should be able to see a message on the Serial Monitor and a blinking onboard LED.