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Keep reinventing

Setting Up Zephyr for ESP32: A Blinky LED Journey

I recently started working with a client on an ESP32 based project. Having prior experience with Zephyr on Nordic boards, I decided to leverage Zephyr's Espressif support for this project. While the documentation mentions the classic "blinky" example, I noticed it lacked the necessary device overlay file for my specific board.

Finding the Right Example

Fortunately, I discovered that the "PWM Blinky" example included sample overlay files I could reference. After compiling the example, I encountered this error when attempting to flash the device: 

([Errno 5] could not open port /dev/ttyUSB0: [Errno 5] Input/output error: '/dev/ttyUSB0')

Running stat /dev/ttyUSB0 revealed that the device belonged to the dialout group. I fixed the permission issue by adding my user to this group: 

sudo usermod -a -G dialout $USER

After rebooting to apply the new permissions, west flash worked perfectly.

Creating the missing overlay file

The basic Blinky documentation explains the need for an overlay file that points to the correct GPIO pin. Based on the PWM Blinky example, I discovered my board (esp32_devkitc_wroom) has an onboard blue LED connected to pwm_led_gpio0_2. I created following overlay file: 

/ {
    aliases {
        led0 = &myled0;
    };
    leds {
        compatible = "gpio-leds";
        myled0: led_0 {
            gpios = <&gpio0 2 GPIO_ACTIVE_LOW>;
        };
    };
};

Success

With the overlay in place(samples/basic/blinky/boards/esp32_devkitc_wroom_procpu.overlay), I compiled the project and it worked: 

west build -p always -b esp32_devkitc_wroom/esp32/procpu samples/basic/blinky

After flashing the board, there it was the blue blinking LED - a small victory that is still the first step and I keep revisiting.

Next up: implementing the project's actual functionality, including WiFi provisioning, ePaper display integration, and LED ring controls.