Wireless Twiddler

Type: Master thesis
Student: Guillaume Ducard

For some wearable computing applications or for disabled people, it is really convenient to use a keyboard with only one hand.

The Twiddler2 from HandyKey Corporation is especially designed to be operated by only one hand. The hand not holding the Twiddler2, is free for other tasks like holding a telephone or a cup, keeping your place when typing a message, jotting a note of paper, etc.

The Twiddler2 provides the same input to the computer as a conventional keyboard. To do this the Twiddler2 uses 12 keys on the front and, on the top, four keys. The top keys are for the thumb, the other four fingers operate the front keys.

At Wearable Computing Lab. a belt integrated computer called QBIC is being developed and embeds a Radio-Frequency transceiver that could be used for communication with a sensor network and a wireless keyboard. The keyboard used at the Lab is Twiddler2 and was so far connected to the PC by a wire.

The project Wireless Twiddler consists therefore of implementing a wireless communication between Twiddler2 and a computer.

Using slave modules form Netarch Project I could connect the Twiddler to one of them and benefit from the RF transceiver on board. This way I could write and test the software for the communication between the Twiddler and the Master.

There is now a stable running software for the Wireless Twiddler that includes the following features:

• To prevent conflicts between the Twiddler and the other nodes of the sensor
• network, the Twiddler behaves also as a slave and has its own address.
• Interfacing the Twiddler is done using a regular asynchronous serial
• transmission at 12.5khz between the Twiddler and the microcontroller. Start and
• stop bit are automatically detected; the parity bit is checked in hardware. This
• solution provides a really robust acquisition of keystrokes.
• The software also includes a buffer that can store up to 5 complete
• keystrokes.
• Software power management reduces current consumption.

I also designed the hardware for the Twiddler and drew the corresponding PCB with the following features:

• The microcontroller MSP430F149 directly interfaces Twiddler using the
• receive pin of UART0 (asynchronous serial port 0).
• Components have been chosen for low power consumption
• The complete system consumes around 14 mA. With two batteries in series
• 3.3V Lithium 950mAh, lifetime equals 65h.
• I designed a PCB that fits inside the Twiddler.
• A spiral antenna is embedded inside the Twiddler and should provide an
• efficient transmission.