Hardware Hacking Projects for Geeks

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Part II: Advanced Hacks, Tools, and Techniques

WARNING

When working with high voltages, I observe what I call the One-Hand Rule. This

means you should keep one hand in your pocket whenever you are handling live,

high-voltage circuits. Do not be tempted to use both hands at once; if one hand

happens to brush against a high-voltage point and the other is touching a ground

point, your body will create a path for electricity to flow across your heart. This

high voltage may cause your heart to stop, which is a very bad thing!

Software Setup Instructions

I decided to keep the software running on the TCU simple. It performs the

basic functions listed here:

• Controls LCD

• Reads button events from the front panel

• Reads and interprets data from the RS-232 serial port

• Controls heating coil selector relay

The TCU may be operated with or without a host PC gateway. When oper-

ated alone, it allows toast pattern selection from the buttons on the front of

the TCU. When operated with a host gateway PC, toast pattern selection

could be based on data gathered from the Internet by sending a command

to the TCU over the gateway serial port.

The software written for the BasicX controller is listed in Exhibit B. The

protocol the TCU uses is simple: when it receives the character A, it selects

the top heating elements; when it receives the character B, it selects the bot-

tom heating elements. The serial communications port is configured by the

software to operate at 19200 bits per second with 8 data bits, no parity bits,

and one stop bit. This can be abbreviated as 19200 bps 8N1.

Program the BasicX controller

You’ll program the BasicX controller via the serial port of a PC running

the BasicX programming software. You will need to type the listing as it

appears in Exhibit B into the BasicX editor. You can also download the

code from http://www.oreilly.com/hardwarehacking.

Start the BasicX software on a PC and open the TCU software file. Connect

the BasicX carrier board to the PC serial port and plug in the board. Select

the “program” option on the BasicX software; this will transfer the soft-

ware from the PC to the BasicX controller. You are now ready to test your

system.

Software Setup Instructions

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