Learning ESP32 using mini projects

Hardware

I got the following items.

1. ESP32 S2 Mini V1.0.0 with type C usb
2. 1.8 inch TFT LCD Display with ST7735 driver board

Project Setup

Folder Structure

The projects are organized in the following structure:

esp/
├── projects/
│   ├── 001-hello-world/    # First project
│   │   ├── CMakeLists.txt
│   │   ├── main/
│   │   │   ├── CMakeLists.txt
│   │   │   └── main.cpp
│   │   └── sdkconfig
│   ├── 002/                # Additional projects
│   └── ...
├── main                    # Symlink to active project's main/
├── CMakeLists.txt          # Symlink to active project's CMakeLists.txt
├── sdkconfig               # ESP-IDF configuration (copied/managed per project)
└── switch.sh               # Project selector script

Each project folder contains its own:

• main/ - Source code directory
• CMakeLists.txt - Build configuration

Switching Projects

Use the switch.sh script to select which project is active:

./switch.sh

The script provides an interactive menu where you can:

• Navigate using arrow keys (↑/↓) or vim keys (j/k)
• Select by pressing Enter

Once a project is selected, symlinks at the root directory (main and CMakeLists.txt) will automatically point to that project's files. This allows ESP-IDF tools to build and flash the selected project.

Dependencies

Dependencies can be found in components.espressif.com.

Installing dependencies

# add a single dependency
idf.py add-dependency "lvgl/lvgl^9.5.0"

Environment variables

The .envrc file manages environment variables for the project. It's automatically loaded by direnv when you enter the project directory.

Setting up .envrc

1. Copy .envrc.example to .envrc:

   cp .envrc.example .envrc

2. Update .envrc with your values (e.g., WiFi credentials):

   export WIFI_SSID="your-ssid"
   export WIFI_PASSWORD="your-password"

3. Allow direnv to load it:

   direnv allow

Note: The .envrc file is gitignored and should not be committed to the repository.

Accessing env from code

You cannot access env variables in code using getenv("WIFI_SSID").

# add this to root level CMakeLists.txt
add_compile_definitions(
    LV_CONF_PATH="${CMAKE_SOURCE_DIR}/main/lv_conf.h"
    WIFI_SSID="$ENV{WIFI_SSID}"
    WIFI_PASSWORD="$ENV{WIFI_PASSWORD}"
)