One challenge of wearable computing is the use of body-worn sensors to detect the context of the ... Figure 1 shows the block diagram of the interface module.
SCIPIO: A Miniaturized Building Block for Wearable Interaction Devices Hendrik Witt, R¨ udiger Leibrandt, Andreas Kemnade, Holger Kenn University of Bremen, Germany TZI, Wearable Computing Lab. {hwitt, quitex, akemnade, kenn}@tzi.de
Abstract. The SCIPIO (“Semi-Complex Intelligent Programmable Input and Output”) module is a miniaturized interface device designed for use in wearable computing applications. It provides a considerable number of flexibly combinable input and output channels in a small and lightweight package (50x30x12 mm, 19 gram). Besides hardware aspects of the SCIPIO interface the paper shows an example of a wearable interaction device that was built with the SCIPIO hardware to evaluate its usefulness for interaction device design for wearable applications.
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Introduction
One challenge of wearable computing is the use of body-worn sensors to detect the context of the user [1]. Another one is to provide wearable computers that are accepted by users in everyday situations such as industrial work environments. Unfortunately, the two challenges are somewhat contradicting as context detection can be improved by using more sensors, but using more sensors and connecting these to the body-worn computer system leads to a complicated and error-prone setup and moreover a reduced user acceptance resulting from the additional weight and a “cyborg-like” visual appearance. Textile electronics [2] might provide a way towards user acceptance, but there are few textile electronic systems available today and of these, even fewer are available outside research labs. In our previous work, the Winspect [3] project, a wearable system for crane maintenance was constructed that used a multitude of cable connections to attach a data glove interaction device, an external battery pack, ultrasound emitters and receivers, a RFID scanner, and a head-mounted display, to a wearable computer. However, the presence of these cable connections led to the rejection of the Winspect prototype by the industrial partner due to work safety considerations.
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Design Requirements
In order to close the gap between a multitude of devices that are connected to a wearable computer by cable and a textile electronics system that integrates all sensing capabilities into the textile fabric, different sensor-boards have been
developed (e.g. [4]). We built a miniature and lightweight sensor interface system as a basis for various wearable interaction devices. The main contribution to the requirements for such a miniature sensor interface came from experiences gained in the Winspect project [3]. They lead us to the conclusion that a generic miniature and lightweight hardware platform with a wireless interface to a wearable computer is required to connect a wide range of equipment. Thus, the following main design requirements have been identified: – – – – –
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small size and lightweight multitude of analog and digital inputs and outputs wireless communication interface energy-efficiency for battery operation cheap, reliable and robust
Hardware Design
The main components of the SCIPIO are a PIC16F88 MCU and an Initium PromiESD Bluetooth module. The MCU contains a RISC CPU, internal RAM and Flash-PROM, a 7-channel A/D-Converter, a PWM generator and a number of digital I/O pins. Figure 1 shows the block diagram of the interface module. The SCIPIO device is very small and of light weight, only 55 x 30 x 12 mm,
Fig. 1. Block diagram of the SCIPIO interface
weighting 19 gram (see figure 2). To optimize battery life, a low-drop switching power supply circuit has been integrated that allows for the efficient operation of the SCIPIO board over a wide voltage range. As a basic feedback system that can be arbitrarily used, the SCIPIO features three differently colored status LED’s and a small piezo speaker connected to the PWM generator for basic visual and audio feedback.
Bluetooth Modul Audio Speaker
Sensor Connectors
Fig. 2. Assembled SCIPIO interface module
3.1
Programming SCIPIO
The SCIPIO board includes a generic firmware that is able to provide the basic functions of the module to the end user without further programming. This generic software allows for operating the device from any Bluetooth-enabled device that is capable to create a rfcomm connection. Devices such as PDAs and mobile phones have been used for this. The SCIPIO operates in rfcomm server mode, i.e., it provides a rfcomm service that a second Bluetooth-enabled device can connect to. It then provides a simple binary interface that transmits the current A/D and I/O readings. In this mode, the visual and audio feedback is used to indicate the connection status of the device. The generic firmware also provides a serial input channel on the SCIPIO device that can transmit data sent by other devices through the bluetooth channel. One device using this secondary channel can be a RFID reader device. For transmitting sensor signals to a Bluetooth attached device, a simple protocol has been implemented, defined by a two byte structure, where the first byte indicates the data type and source and the second byte contains the actual data. The types of data transmitted and the frequency of the transmission can be configured during run-time by sending control commands to the device. By these control commands, the visual and audio feedback can also be activated. The SCIPIO’s generic firmware can also be replaced by an application-specific program. The SCIPIO board provides interfaces for in-circuit programming and testing with standard PIC development tools. The generic firmware source code is available to the end users upon e-mail request to the authors and thus provides a starting point for new development.
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Building a wearable interaction device
To prove and evaluate the usability of the SCIPIO hardware for wearable computing applications, we developed a wearable interaction device that makes use of SCIPIO. The developed device is a data glove based interaction device intended for use in explicit interaction in an industrial environment. 4.1
Hardware integration
To use SCIPIO for the management of needed sensors to build the data glove, three kind of sensors have been included into the SCIPIO setup. A dual axis tilt-sensor is used for hand-rotation activities, e.g., to navigate through vertical lists. Three micro buttons have been integrated into fingers of the data glove to offer arbitrarily usable action triggers for an application. Finally, an RFID scanner has been placed at the side of the hand to let a user easily scan a RFID tag, e.g. to determine a location context. The visual feedback system was used for basic status information such as connectivity or battery power, whereas the piezo speaker has been used to give audio feedback if a RFID tag has been successfully scanned. This specific sensor setup of the SCIPIO hardware results in a customized protocol with six different data byte types for the sensor data to be transmitted. One type for the 3 different button states, one for scanned RFID’s and two types of the remaining four for the two axis of the tilt-sensor, because tilt-sensor values can occur in a range of 512 different values. 4.2
Wearing concept
Besides hardware integration we designed a special wearing concept based on three different gloves that build the actual data glove. Figure 3 shows this layer concept. We chose this concept to provide an approach to hygiene instructions required in several application domains when wearable computers are used, e.g., in the medical domain. Regarding this, the inner glove is used for hygiene purposes whereas the middle glove is used to fix the controller hardware as well as sensors and buttons. Finally, the outer glove can be chosen arbitrarily according to an application domain, e.g., a robust protection glove for maintenance tasks.
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Conclusion and Future Work
In this paper we presented the SCIPIO interface hardware and its design towards a flexible, extendable, small and lightweight interface device for various wearable computing aspects mainly including interaction device development and context recognition. The design we presented was based upon our experiences in previous projects in wearable computing. Furthermore, we showed how the SCIPIO module was integrated as a central component into the development of a wearable
Fig. 3. Wireless data glove interaction device that uses SCIPIO
data glove interaction device that can be used for explicit interaction in several application domains, such as maintenance. Future work will include improvements of the SCIPIO hardware regarding its size by using even smaller components as well as extending the functionality of the firmware. Beside this, we are currently working on an improved textile integration of the SCIPIO hardware into the data glove interaction device. One major issue here will be, for example, the uses of conductive yarn.
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