RAYSHOBBY.NET

Looking for new projects to do with SquareWear 2.0? Here is an idea: combine SquareWear 2.0 with touch sensing to make a digital piano! It works as a standalone project and no additional hardware is required. Take a look at the video first:

How does this work? First, SquareWear 2.0 has a built-in buzzer, so it can already make sound. Next, touch sensing is detected in software. It basically exploits the principle of capacitive sensing: every time you touch an Arduino pin, it slightly alters the capacitance of the pin. This change of capacitance can be detected using a variety of methods. The simplest is to set the pin to digital input mode, and turn on the internal pull-up resistor. This will start charging the capacitor. By detecting the time it takes to charge the capacitor, you can infer the capacitance, and in turn tell if a finger touch has occurred on the pin. That’s it! Because SquareWear maps out available pins to large pin pads, this makes it particularly well-suited for touch sensing.

So I wrote a quick demo as a proof-of-concept. First, I found a function that implements the capacitive sensing from the Arduino playground website. It basically returns a touching sensing value, which can then be compared to a threshold. You may need to adjust the threshold to increase or decrease the sensitivity. The demo scans through all 12 pins available on the SquareWear 2.0 and plays a tone for 125 milliseconds if a pin touch is detected. As a result, the buzzer makes a chiptune type of sound. The code also uses the on-board pushbutton to switch between three octaves: C3, C4, and C5. The LED will blink when a tone is played.

A few notes and quirks:

• The code works the best if you plug in a USB cable connected to your computer.
• You can also moisten your figures to help increase the touch sensitivity.
• If you unplug the USB cable, it generally helps if you use one hand to hold the battery, or the VCC or GND pin. You may need to cover the ISP pins on the back side to avoid touching them. Holding the battery, VCC or GND helps amplify small capacitive changes.
• The MOSFET pins (D3, D5, D6) do not seem to work well without the USB cable. To be honest, I was surprised that these pins even worked at all, because the pads are not directly connected to the pins (rather, the connection is through a MOSFET). So if you need, you can modify the source code to disable these pins.

The demo code is available in the SquareWear 2.0 software package on Github. The direct download link is below:

• Download SquareWear Digital Piano Demo.

I will keep posting new project ideas in the upcoming weeks. SquareWear 2.0 is available for purchase at the Rayshobby Shop. At a price of $22 and with a load of built-in components, it’s a great little gadget to help you learn Arduino programming, and build wearable as well as general-purpose electronic projects. Hope you like this demo and your support is greatly appreciated!

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.

The bootloader is based on Frank Zhao’s USnoobie project. To enter programming mode, press and hole the on-board tactile button, then turn on power. This will allow the microcontroller to bootload as a USBasp programmer, which is supported by Arduino. On Linux and Mac, you don’t need to install any driver; on Windows, you need to install the USBasp driver (come on, Microsoft!), which is included in the SqureWear software package. The board has internal assignments for the following pins:

• D2/D7: USB D-/D+.
• D4: tactile button.
• D8/D12/D13: LED red/green/blue channel.
• D9: buzzer.
• A0/A1: light/temperature sensor.

The other pins are all mapped out to sewable pin pads with large holes. You can either stitch conductive threads through the pins, or solder wires directly onto the pins, or solder snaps to make it easy for quickly attaching or detaching the board from fabric.

I should mention that pins D3, D5, D6 are internally connected to n-channel MOSFETs and these pins are suitable for driving high-current load (up to 250mA each pin). This is very useful if you want to switch a large number of parallel LEDs, a motor, a muscle wire, a heat wire etc. You can even combine two or three of them together to drive higher current. If you are familiar with Arduino, you should know that these three pins also support hardware PWM, so you can use them to control the brightness of LEDs, the speed of a motor etc. Technically I call them ‘power sink pins’ because unlike a standard output pin, they can only connect or disconnect a component from ground (sink). So the right way to use them is by connecting the positive wire of your component to Vcc (or external power), and the negative wire to one of the MOSFET pins.

Anyways, I want to keep this post short, so I will leave you to find more details in the video tutorial above, and the user manual in the software package. If you are interested in buying SquareWear 2.0, it’s available for purchase at the Rayshobby Shop. Feel free to leave comments below, or on the forum. Thanks!