This is a very practical I2C breakout that can be used in the digital to analog and analog to digitan converting processes. There is a 8-bit converter PCF8591 IC on the board.
There is a trimpot, NTC temperature sensor and a LDR light sensor on the board that can be used in the example application. It is possible to change the I2C adress using the jumpers and you can use 8 of this moduls at the same time.