This is a short example for attiny84 showing how to measure temperature and relative humidity with the Sensirion SHT4x sensors series. It communicates on the I2C bus by bit banging. Control and conversion functions are provided.

The main loop wakes up the attiny84 every 8 seconds, requests a measurement from the sensor, and then sends the attiny back to sleep.

• AVR GCC toolchain
• avrdude
• adequate programmer (Makefile is for USBasp)

make & make flash

• It may fit (not tested) in an attiny44 by using the MCU's I2C driver (see Universal Serial Interface in attiny datasheet)
• The setup and main loop sections of main() function may be split to match Arduino's nomenclature