A MOSFET turns the backlight LEDs on/off and a 4.7ohm resistor limits the maximum current through the LEDs. This makes it quite easy to control the backlight with a PWM signal to adjust intensity. 8297A-AVR-04/10 The SPI interface The Display Xplained module uses a simple SPI interface to communicate with the LCD module. This consist of a Chip-Select (CS) line, a clock line (SCL), and two data lines (SDI/SDO). The SPI is operated in mode 3, i.e. inactive clock is ‘high’, and data is latched on r