How can I interface a passive segment LCD display with the EFM32?
Segmented LCD displays are commonly used to display information. The low-power LCD driver in EFM32 devices allows applications to utilize an LCD display even in energy-critical systems. Passive segment LCD displays (Liquid Crystal Display) are built by sandwiching the liquid crystal between two glass plates. Using the voltage dependent, polarizing properties of the liquid crystal material, light transmission through the LCD glass can be controlled. This light polarization is affected in different ways when voltage is applied over the liquid crystal and when it isn't.
Fig: One LCD segment with and without voltage applied
An EFM32 built-in LCD driving peripheral has many features, such as:
Multiplexing - the EFM32 LCD driver can multiplex up to 8 common lines, and the multiplexing waveforms and bias voltage levels are automatically taken care of within the LCD driver peripheral.
Animation and Blinking - of specific segments enabled by the LCD driver without any software intervention.
LCD Interrupts - the single interrupt source in the LCD driver is the frame counter interrupt and it can be used to time and execute display updates and animation changes.
Minimize Energy Consumption - the LCD driver is a very low power peripheral that can operate in EM2 energy mode from the low frequency oscillator. Connecting an LCD display to the EFM32 increases energy consumption because of the capacitive load, but this can be minimized by configuring the lowest possible display refresh rate that does not cause flickering.
Read the complete application note here for more details on all of the above and for software examples.