I made a little board for a SHT21 humidity and temperature sensor from Sensirion. There are several versions with I2C interface, PWM output and SMD/analog interface.
I’ve got the one with Sigma Delta Modulation (SMD) output, is a bit-stream of pulses; the more high pulses the higher the value in the full measurement range. A low-pass filter convert the pulse stream to an analog voltage signal.
It has a control pin (SCL) to select between humidity or temperature output. SCL high yields humidity output, SCL low yields temperature output.
I made a simple sketch in Energia to test it out using an MSP430G2553. P1.6 selects between humidity or temperature and P1.0 is used as the ADC input.
…and logged both temperature an humidity.
That’s it, a simple and nice sensor…