tail -f ZS64.log » iic http://blog.zs64.net Random Ramblings Sat, 18 Jun 2011 17:16:01 +0000 en hourly 1 http://wordpress.org/?v=3.2.1 TEMPer USB Thermometer http://blog.zs64.net/2010/01/temper-usb-thermometer/ http://blog.zs64.net/2010/01/temper-usb-thermometer/#comments Fri, 01 Jan 2010 20:45:35 +0000 stb http://blog.zs64.net/?p=220 Measuring temperature in a PC should be easy: after all, most mainboards have extensive monitoring capabilities for temperature and voltage levels built-in. Unfortunately, very few of these facilities are documented properly, and software support is lacking. Instead of trying to navigate the maze that is lm-sensors (which isn’t even available for FreeBSD), I decided to look for some USB-based solution.

There’s a reasonably cheap chinese USB thermometer called TEMPer. I got mine from Brando for 12 Euros. It’s a USB-to-serial chip from WinChipHead. It’s DTR, RTS, and CTS lines are used to connect a LM75 I²C temperature sensor. To talk to the LM75, you need some bit-banging driver.

I’ve put together a command line utility for the TEMPer that can program the built-in thermostat (TEMPer has a LED connected to that output) and print out temperature measurement data. It does it’s job, and might serve as an example on how to do I²C over a simple interface.

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