[www.embeddedarm.com]

It has long been regarded that the UNIX-like OS NetBSD is portable to every type of machine except perhaps your kitchen toaster. Technologic Systems, however, has conquered this last frontier. Using one of its rugged embedded TS-7200 single-board computers housed inside the empty space of a standard 2 slice toaster, Technologic Systems has designed a functional NetBSD controlled toaster.

NetBSD was ported to the toaster by Jesse Off (an engineer at Technologic Systems). When asked details about the week-long effort, he replied, “NetBSD is well laid out for this type of embedded application development. I was most worried about physical things such as fitting the hardware inside the case and the board being able to survive 60 seconds at a time a half centimeter away from an 800 watt burner element. A regular PC can’t even survive room temperature without heatsinks and fans, and the TS-7200 has neither.” The end-design has no thermal issues and will not let the user toast if things start getting close to the temperature margins of the internal components measured by the onboard temperature sensor.

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Technical Details

All peripherals had NetBSD drivers written that allow their manipulation and readback. The interface to toaster hardware uses the sysctl API. sysctl allowed for the easy coding of the toasting finite state machine as a simple shell script. The 4 LED’s are configured as PWM style outputs to vary brightness/blink-rate. Temperature is tracked using the TS-7200 onboard TMP124 sensor. This temperature sensor has .0625 degC precision and the kernel driver takes multiple measurements averaged over time to interpolate even higher precision. (the sysctl returns millionths of a degree C) The burnlevel knob is a potentiometer connected to channel 0 of the 12-bit MAX197 ADC which returns a number 0-4096 to the system also via sysctl.

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A full NetBSD installation is on the 512MB compact flash attached to the TS-7200. This includes self-hosted compilers, FTP/telnet server, ssh client/server, crypto libraries, kernel/userlevel debuggers, and standard UNIX utilities. Apache with PHP is also installed on the TS-7200 and presents some CGI programs to control the LEDs, play music, etc… Since the 4×40 LCD is attached as a generic console, manipulating text files is also reasonably possible using installed text editors, though admittedly using vi on a 4 row text display is not particularly productive.

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