February 21, 2026
Source code that accompanies First Look at the Seeed Studio XIAO ESP32C3.
Note: That post, last updated in July 2024, is now out of date and will be reworked in the future.
Table of Content
- 1. Introduction
- 2. Arduino IDE Notes
- 3. PlatformIO Notes
- 4. List of Projects
- 5. Project Notes
- 6. Related Work
- 7. License
The XIAO ESP32C3 is a relatively recent addition to the Seeed Studio XIAO series of diminutive development boards. It is based on the Espressif ESP32-C3 SoC which has a RISC-V core.
It should be possible to compile each project on the Arduino IDE or pioarduino IDE without any need to install anything other than this repository.
Arduino sketches must have an .ino file name extension and must be contained in a directory that has the same name as the Arduino sketch (excluding the extension). Consequenty the 01_pin_names project containts a directory named pin_names that in turn contains the Arduino sketch pin_names.ino. That sketch is basically empty as it is a long comment only. This is not a problem because the Arduino IDE will import all source files found in the sketch directory. The actual code is in main.cpp which is the default name of a PlatformIO project.
To compile and then upload the sketch in the Arduino IDE, click on the File top menu, click on Open..., then navigate to the pin_names.ino file and open it with the system file manager.
Some sketches require third-party libraries. To make these sketches self-contained, private copies of the needed libraries are included in the libraries directory.
The Arduino IDE will find these private libraries if the Sketchbook location in the Arduino Preferences is set to the parent directory, xiao_esp32c3_sketches. Details can be found in libraries/README.md.
Where a private library is included, only the necessary files were added. Please obtain the full library from the original source if it is to be used in another project.
Because of the Arduino sketch naming constraints, the main.cpp file of a project is not stored in the src directory. To work around this change, a src_dir entry is added in the platformio.ini file to provide the name of the directory in which main.cpp is found. That will be the name of the Arduino sketch as shown here for the 01_pin_names project.
[platformio]
; Make the Arduino IDE happy (.INO file must be in a directory of the same name)
src_dir = pin_names
...Pioarduino will "convert" the Arduino sketch, but that is of no consequence since it contains only comments.
The local copies of third party libraries will be used by pioarduino by default. This is achieved by a lib_dir entry in the configuration file where needed.
[platformio]
; Make the Arduino IDE happy (.INO file must be in a directory of the same name)
src_dir = async_web_led
lib_dir = ../libraries
...Except for 00_sys_info and 01_pin_names, these projects control an external LED that is connected to one of the I/O pins of the XIAO ESP32C3.
| Project | Purpose |
|---|---|
| 00_sys_info | Display information about the ESP32 system. |
| 01_pin_names | Display the mapping of XIAO ESP32C3 Arduino pin names to gpio numbers and som useful macros. |
| 02_blink_led | Use digitalWrite, delay and io interrupts to blink a LED attached to any I/O pad of the XIAO. |
| 03_button_led | Use digitalWrite and digitalRead to toggle a LED on and off. |
| 04_web_led | Use a Web server to toggle a LED on and off. |
| 05_async_web_led | Use an asyncronous Web server to toggle a LED on and off. |
| 06_ble_led | Use Bluetooth to toggle a LED on and off with the ArduinoBLE library. |
| 07_ble_led | Use Bluetoooth to toggle a LED on and off with the ESP32 Arduino core BLE libraries. |
| 08_pulse_led | Use analogWrite to pulse a LED attached to any I/O pad of the XIAO (pulse width modulation). |
In both 04_web_led and 05_web_led the SSID and password for the Wi-Fi network must be provided in a file called secrets.h in the directory containing the source code. There is a model called secrets.h.template in the same directory that can be edited and saved under the correct name.
When attempting to compile the 07_ble_led/ble_led sketch in the Arduino IDE, it is necessary to
move the local libraries/ArduinoBLE library outside the libraries/ directory. Otherwise there will
be name conflicts with the ESP32-Arduino BLE libraries. More details in libraries/README.
There is a MicroPython web server script described in 14. MicroPython: Web Controlled LED which is similar to the 04_web_led project. The source is available here: upy_web_led.zip.
It may be interesting to look at supermini_esp32c3_sketches which are about a class of slightly bigger ESP32-C3 development boards. That repository contains modified versions of projects such as async_web_led and ble_led2 that can be used to investigate connectivity problems. Some Super Mini boards are known to have problems related to the circuit between the microcontroller and the onboard ceramic antenna or with the latter.
Finally, xiao_esp32c6_sketches and xiao_esp32c5_sketches are about the XIAO ESP32C6 and XIAO ESP32C5 development boards by Seeed Studio that are also based on a RISC-V microcontroller.
Copyright 2023-2026 Michel Deslierres. No rights reserved.
While the copyright pertaining to included libraries must be respected, all the code by Michel Deslierres in this repository is in the public domain. In those jurisdictions where this may be a problem, the BSD Zero Clause License applies.