Hardware Architecture

The eWatch hardware architecture consists of: the main CPU, sensors, power control, notification mechanisms, and wireless communication. The main CPU is a Philips LPC2106 ARM7TDMI microcontroller with 128Kb of internal FLASH and 64Kb of RAM. The LPC2106 is a 32bit processor capable of software controlled CPU scaling up to 60Mhz. eWatch communicates wirelessly using a SMARTM Bluetooth module and an infrared data port for control of devices such as a television.

Sensor data is acquired using an external TLV1544 10bit ADC and can be stored in a 1Mb external FLASH device. eWatch is capable of sensing temperature, light, two axes of acceleration and audio at user controllable sampling intervals up to 100Khz. A MAX4061 amplifier is used for audio conditioning. We use an ADXL202 MEMs accelerometer to measure the planar acceleration of the user's hand. The user can be notified using a 128x64 pixel display, an LED, vibrating motor and tone generating buzzer. Three push buttons are distributed around the outside of the housing in the standard configuration of a digital watch.

eWatch is powered by a 3.6 volt 700mAh rechargeable lithium polymer battery with a linear regulator active during peak voltages and a DC to DC voltage pump as the battery drains.
  • ARM7 processor (32-bit, 80 Mhz,64kb RAM, 128kb Flash)
  • Flash memory (1MB)
  • 10 bit ADC
  • Sensors
    • microphone
    • dual axis accelerometer
    • light sensor
    • skin temperature sensor
    • three buttons
  • Notification
    • Vibration Motor
    • Audio Alert
    • 128x64 monochrome LCD display, blue luminescent backlight
    • LED
  • Communication
    • Bluetooth
    • IR output
    • RS232
  • Power
    • 700mAh Lithium Polymer Battery
    • 2 Day Battery Life
    • Recharges in 1 hour
    • CPU Frequency Scaling
    • Battery Monitoring
    • Power Gating for all peripherals

2004 Carnegie Mellon University