The Lux Plug is a small board containing the TSL2561 light sensor. This tiny sensor communicates directly over I2C. There is a “LuxPlug” class in the JeeLabs Ports library to interface with this sensor and return the Lux level as an integer in the range 0-64000. The gain can be either 1x or 16x, giving 20 bits of dynamic range.
An I2C bus running at 3.3V is used as interconnect, with all the power and signal lines brought out to to both sides of the board to allow daisy-chaining with other I2C-conformant boards.
The Assembled Lux Plug comes with the SMD-sized TSL2561 chip and decoupling capacitor already soldered onto the board. Headers for this and all other JeeLabs plugs can be found here (straight) and here (right angle).
The PCB Only version contains just the printed circuit board for the Lux Plug. No parts, no headers.
The documentation and full design details are freely available at JeeLabs.