This pHAT allows you to connect multiple I2C devices with the same address onto a single I2C bus.
It's a tidy and compact way of connecting an I2C multiplexer IC (TCA9548A) to a Pi - ideal for coupling with a Pi Zero W for a neat remote monitoring and graphing setup (though it's also compatible with all models of Pi with a 40 pin GPIO).
The EEPROM automatically loads the correct i2c-mux overlay and turns it into 8 individual I2C buses (/dev/i2c-3 to /dev/i2c-10) allowing direct communication with the I2C devices as normal (via i2cdetect / i2cget / i2cset / Python SMBUS, etc).
For each multiplexed output there are 4 pins:
The "V" output can be altered from the default 3.3 volts to 5 volts by cutting the PCB trace between V and 3v3 and bridging V to 5v. The 3.3v supply is taken directly from the Pi 3v3 rail so care should be taken not to overload it.
Please note: product colour may vary, some production runs have been on a green PCB, but there is no functional difference :-)