Picoclick C3T Is the World's Smallest IoT Button and It Has a RISC-V Processor

WiFi-enabled buttons send an MQTT message or REST call from a single button push. This simple action enables a wide range of automation activities. For example, at one point, online retailers gave them to customers to quickly purchase replacement products. Similar to these limited "Dash buttons," a maker moekoe has used an Espressif ESP32-C3 to develop Picoclick C3T, the world's smallest IoT button. Not only does it contain a RISC-V core, but it also supports more than a single button push.

Picoclick C3T is a scant 10.5 x 18-millimeter board. One side has the ESP32-C3 SoC, while the other has a pushbutton and RGB LED. When activated, the board can send a message via WiFi (or Bluetooth). Unlike some Dash button designs, this one supports single, multi, and long button presses.

A straightforward way to implement a WiFi pushbutton is to deep sleep a microcontroller. For example, pressing the button causes the microcontroller to reset, run the code that sends its message, and then go to sleep. While efficient, this method means the button push is a one-time-only action.

Moekoe developed a power latching circuit for Picoclick C3T. This design change allows the microcontroller to check for additional button actions when it powers up and before shutting itself off. The added benefit to the latching circuit is that while inactive, the Picoclick draws a meager 3 uA of current.

The C3T part of Picoclick's name appears to be a nod to the SoC running the Dash button. Unlike the base ESP32 and ESP32-S series chips, the Espressif ESP32-C contains a RISC-V core. This SoC runs up to 160 MHz and includes radios for WiFi 2.4 GHz and Bluetooth Low Energy (BLE).

Programming Picoclick C3T requires either PlatformIO or Espressif IDF. Moekoe says support in the Arduino IDE may be possible, but configurations are necessary that the framework does not (easily) support.

The ESP32-C contains a native USB interface, so Picoclick does not need a separate USB-to-serial converter. In addition to programming support, the USB-C connection powers the onboard LiPo charging circuit. Since Picoclick C3T is small, moekoe optimized the charge rate for tiny LiPo batteries.

Over on the Picoclick-C3 GitHub repo, you can find the schematic, bill of material, Gerber files, a case design, and code examples.

Moekoe sells Picoclick-C3T for $22 on Tindie. To avoid shipping restrictions, you must source the battery on your own. But, heads up, demand for this clever button has been high, so if they are not in stock, make sure you join the waitlist!