Source code that accompanies the July 2024 revision of First Look at the Seeed Studio XIAO ESP32C3.

Table of Content

• 1. Introduction
• 2. Arduino IDE Notes
  • 2.1. Third-party libraries
• 3. PlatformIO Notes
  • 3.1. Third-party libraries
• 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 with PlatformIO or in the Arduino 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

PlatformIO will "convert" the Arduino sketch, but that is of no consequence since it contains only comments.

PlatformIO automatically downloads the needed libraries and installs them in the local .pio/libdeps/directory at compile time. This is because the library dependencies of each project are defined in the latter's platformio.ini configuration file.

[env:seeed_xiao_esp32c3]
...
lib_deps = me-no-dev/ESP Async WebServer@^1.2.4

To use the private copy of the libraries included in this repository, remove or comment out the lib_deps= line in platformio.ini and replace it with a lib_dir= entry.

[platformio]
src_dir = async_web_led
lib_dir = ../libraries

[env:seeed_xiao_esp32c3]
board = seeed_xiao_esp32c3
framework = arduino
platform = espressif32
monitor_speed = 460800
;lib_deps = me-no-dev/ESP Async WebServer@^1.2.4

Except for 01_pin_names, these projects control an external LED that is connected to one of the I/O pins of the XIAO ESP32C3.

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.

It is not easy to use the ArduinoBLE library in the ArduinoIDE because of name conflicts with the BLE library included in the ESP32 Arduino core. Consequently ArduinoBLE is not included in the librairies directory. Comments in 06_ble_led/ble_led/ble_led.ino explain how the sketch could be compiled in the Arduino IDE, but it is suggested to skip this particular sketch and to use 07_ble_led only in the IDE.

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 is about the XIAO ESP32C6 which is the newest member of the XIAO series of development boards by Seeed Studio that has the ESP32-C6 RISC-V microcontroller.

Copyright 2023, 2024 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.