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Major Components of the CanSat Bus
The CanSat bus consists of a gutted FRS radio (communications subsystem), the BASIC Stamp board (on-board computer), and a data message encoder/decoder.   Message processing is handled by the common architecture software stored in the memory of the on-board computer.   The code works in concert with the data encoder/decoder chip.
The Communications Subsystem

14 Channel 300mW Sports Personal FRS Radio w/19CTSS by Radio Shack [210-1822]

We removed Radio Shack's attractive blue cover, disconnected the speaker, and scooped out the electronics for use as our CanSat's comm system.   Wanna see how it looks on the inside?   Go to the Photos /Schematics page.   Wanna see how the radio innards get hooked up to the other components?   Go to the Photo / Schematics page.

Some specs:

Minimum Battery Life (alkaline)
(Standby): 85 Hours
(Transmitting): 4 Hours

Dimensions (HWD): 3.3 x 2.2 x 1.1 Inches (85 x 56 x 28 mm)
Weight (with batteries): 0.275 lbs (125 g)

Tech Docs of Model 210-1822 FRS 2 Way Radio


CM8880 DTMF Tranceiver chip by California Microdevices

The CM8880 is a Dual Tone Multi Frequency chip that is capable of transmitting and receiving touch tones.   Yes it's the same touch tones in your phones.   It's "Dual Tone" because it takes two tones (a low frequency tone and a high frequency tone) for each number key.

We use the DTMF tranceiver to encode and decode messages for sending and receiving sensor data and commands from the ground station.
Here is a sample App Note for use with the BASIC Stamp.

CM8880 Spec Sheet

The On-Board Computer
Parallax BASIC Stamp II.

It's a tiny little computer.   You can make it do all kinds of stuff.   And, it costs 49 bucks a pop.

The EEPROM (Electronically Erasable Programmable Read-Only Memory) is the hard disk.

There is 32bytes of RAM (Random Access Memory).

The Interpreter reads and implements PBASIC (Parallax's BASIC programming language. See link below for PBASIC Manual download.) code that the user writes.

There are 16 I/O pins for external interface to peripheral electronic components such as sensors and motors.   These are the data bus ports connecting to the subsystems of the vehicle.

BASIC Stamp FAQS

BASIC Stamp Spec Sheet

BASIC Stamp Documentation Downloads

Go to the Photos/Schematics page to see how the radio, BASIC Stamp, and the DTMF chip relate to each other and how they hook up.