It's about one year ago that I ordered the DHT11 low cost humidity and temperature sensor. Now I found some time to make something useful with it: A USB stick sensor node.
When plugged in, it provides a serial interface which outputs the data in a readable format once a second.
This project utilizes only an DHT11 1-wire sensor and the programmer ez430U, which comes with every ez430-Kit from Texas Instruments. The ez430U has a MSP430F1612 micro-controller on it accompanied with a TUSB3410 chip for serial to USB conversion.
To re-program the F1612 you need a grown-up (4-wire capable) JTAG tool and a connection to the RESET and JTAG pins of the device. For our all convenience TI prepared already the test points TP2 (reset) and TP4-7 (JTAG) for that and you only need to solder a 5-pin header to it.
The DHT11 uses a proprietary 1-wire protocol with a pulse width coding. I developed a full timer and interrupt based code to request and decode the sensor data from the DHT11 while the main controller is powered down. As the sensor should only be read-out once a second, the MSP430 sleeps also during this period.
I've uploaded the complete project with some extra functions to read and write the EEPROM for the USB controller to GitHub.