Developed For: Sontra Medical jointly with TechEn, Inc.
Key Technologies:
Microprocessor: Microchip PIC16F819
RF Device: TI CC2550 Transmitter
Battery: 3V Lithium coin-cell
The Problem:
Design the electronics and firmware for a wristwatch-size device with
a Gluscose sensor that could operate continuously for 28 hours,
reliabily transmitting information over short-distances in a hospital critical care unit.
The Solution:
The small circular PCB contains contained a Microchip PIC6F819 processor connected serially to a
TI CC2550 930MHz transmitter. The Glucose sensor produces an output voltage and was
connected to one of the PIC's Analog Input channels.
The device was programmed to sleep most of the time, wake-up periodically to convert the
analog signal to a digital value. Several samples were acquired each minute;
the PIC combined and filtered the samples to produce a "final" value.
The "final" digital value along with some information about sensor temperature was transmitted
several times over the following minute on two independent frequencies.
The repetition of the transmitted data and the use of two frequencies improved the reliability of
the communicated data.
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