Segment LCDs are available in two forms - segment LCD glass and the segment LCD module, which comes with inbuilt driver. Many times, it is difficult to get all the required display features on a LCD module. One possibility is to use a custom LCD glass and an external driver. But this increases the cost of the system. Cypress PSoC chip can do segment LCD glass drive besides executing some other major tasks with its configurable digital/analog hardware and with its 8-bit MCU. It integrates multiple functions of the system within a single chip offering significant BOM savings.
Segment LCD Drive in PSoC 1
PSoC Designer provides SLCD user module (UM) that can directly drive a multiplexed segment LCD. The SLCD UM has the following features:
Drives LCD with ½ bias
Supports 2, 3, and 4 common LCD
30 150 Hz refresh rate
Supports Type A waveform
Contrast control Feature
Support for Numeric (7 segment), alphanumeric (14 and 16 segment) and special symbols
SLCD is a firmware based module where the CPU generates the ½ bias waveforms by configuring the pins and associated registers. To time the refresh events, periodic interrupts are generated to the CPU using a timer. This timer is embedded within the module.
SLCD module provides two unique techniques to drive the LCD: