Hardware Hacking Projects for Geeks

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Chapter 5, How to Hack a Furby (and Other Talking Toys)

Some of these are cleared by hardware after interrupting. When the inter-

rupt occurs, the CPU will jump to the location shown. You need to write

the code to handle that interrupt and place it at that address. If the code is

more than a few bytes, you will need to put a jump instruction in the vector

and put the interrupt service routine somewhere else where there is room.

See the following table:

Input device Priority Interrupt vectors to

External 0 1 0x0003

Timer 0 2 0x000B

External 1 3 0x0013

Timer 1 4 0x001B

PCA interrupt 5 0x0033

Serial port (PC) 6 0x0023

Timer 2 7 0x002B

The last instruction in your interrupt service routine is always “RET” to

return to whatever was happening when the interrupt arrived (that’s why it

is called an “interrupt”). More specific information can be found on page

19 of the Phillips P89C51 data sheet.

Project Demo

Your new Furby hardware should now be up and running. All you have to

do is code some simple (or complex) Furby applications. The web site http://

www.appspec.net/index.html has a few examples from which to start.

Extensions

Not only can you change the vocabulary and voice of the Furby, you can

use the sensors in interesting ways. You could, for example, turn the Furby

into a simple motion-sensing alarm system that spouts off amusing phrases

when it sees movement.

Extensions

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