SquareWear 2.0 – an open source wearable Arduino
This is a long delayed post. I am glad I finally finished making a video for it, and it’s time to introduce SquareWear 2.0 — an open-source, wearable Arduino microcontroller board.
At heart, SqureWear 2.0 is an Arduino running at 3.3V and 12MHz. It has built-in mini-USB port for uploading programs, charging lithium batteries, and creating a serial communication channel. It comes with a lot of useful built-in components, such as a color LED, a general-purpose push-button, a buzzer (yup, you can make it sing a tune), light sensor, temperature sensor, three MOSFETs (to drive high-current load). Even better, it has a built-in rechargeable lithium coin battery (you heard it right: rechargeable coin battery!), so you can power your project right away without requiring external power supply. Every time you plug in the mini-USB cable, it charges the coin battery automatically. Better still, if you want a beefier battery, you can plug in an external lithium battery through the on-board battery jack. The built-in lithium charger can charge external battery as well. Overall SquareWear 2.0 packs a lot of useful features on a 1.7″ x 1.7″ board. It’s great for wearable electronic projects as well as general-purpose microcontroller projects. Below is a summary of built-in components:
- ATmega328 running at 3.3V, 12MHz.
- MCP1700 3.3V / 250mA LOD.
- MCP73831 lithium charging chip (configured to charge at 35mA).
- MCP9700 temperature sensor.
- 10K photo-resistor.
- Four 2N7002 MOSFETs.
- 5050 color LED.
- 8.5mm SMT buzzer.
- 6mm SMT tactile button.
- Charging indicator LED.
- LIR2032 rechargeable lithium coin battery (45mAh capacity).
- 2.0mm JST connector for external lithium battery.
- SMT mini-USB port, and power switch.
Last year around this time I released SqureWear 1.1, which is based on Microchip’s 18F14K50 microcontroller. It’s pretty neat, but over time I’ve received quite a few requests to develop a similar board based on the Arduino. This inspired me to work on SquareWear 2.0. Many design choices, including components I selected to put on board, were based on feedback and experience at various wearable electronics workshops I organized.
With SquareWear 2.0, programming is now done through the Arduino software. You can make use of thousands of available Arduino libraries to help build your project. Similar to the standard Arduino, it is based on a ATmega328 microcontroller. However, SquareWear does not have a separate USB-to-serial chip. Instead, it simulates USB functionality all in software, using the V-USB library. It has a USBasp bootloader, and can perform serial communication through USB. It can also simulate a mouse, a keyboard, or other human interface devices (see V-USB example projects). While software-based USB is not that fast, it really helps reduce the cost and size of the board by having one chip to carry out all the tasks. That’s why we can offer SquareWear 2.0, with all the aforementioned components and features, at a very competitive price.
For more detail: SquareWear 2.0 – an open source wearable Arduino