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Silicon Laboratories EFM32 Series Quick Start Manual
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Silicon Laboratories EFM32 Series Quick Start Manual

1 lcd driver
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AN0057.1: EFM32 Series 1 LCD Driver
This application note provides a description of how passive seg-
ment LCD displays work and how they can be interfaced with the
EFM32.
This application note includes:
• This PDF document
• Source files (zip)
• Example C-code
• Mulitple IDE projects
silabs.com | Building a more connected world.
KEY FEATURES
• The ultra-low power LCD driver has
internal bias voltage circuit to minimize
external components.
• The charge pump mode enables it to
provide the LCD display up to twice the
supply voltage of the device.
• The power consumption of the LCD panel
itself can be lowered through the use of
charge redistribution.
• The LCD driver supports autonomous
animation and blinking in deep sleep
without CPU intervention.
Rev. 1.05

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Summary of Contents for Silicon Laboratories EFM32 Series

  • Page 1 AN0057.1: EFM32 Series 1 LCD Driver This application note provides a description of how passive seg- KEY FEATURES ment LCD displays work and how they can be interfaced with the EFM32. • The ultra-low power LCD driver has internal bias voltage circuit to minimize This application note includes: external components.

  • Page 2: Device Compatibility

    AN0057.1: EFM32 Series 1 LCD Driver Device Compatibility 1. Device Compatibility This application note supports multiple device families, and some functionality is different depending on the device. EFM32 MCU Series 1 consists of: • EFM32 Giant Gecko (EFM32GG11) • EFM32 Tiny Gecko (EFM32TG11) silabs.com | Building a more connected world.
  • Page 3 AN0057.1: EFM32 Series 1 LCD Driver Introduction to LCD Segment Displays 2. Introduction to LCD Segment Displays Segmented liquid crystal displays (LCDs) are a common way to display information. The extreme low-power LCD driver in the EFM32 enables many applications to use an LCD even in energy critical systems. This document will both discuss how certain types of LCDs work, how they are driven and how to minimize their energy consumption.
  • Page 4 AN0057.1: EFM32 Series 1 LCD Driver Introduction to LCD Segment Displays 2.2 Driving a Display Segment Segment LCDs do not have any internal driving circuitry. All the display pins are directly connected to each side of the corresponding segment. The simplest LCD imaginable consist of only one segment with two electrical connections, one for each side of the segment.
  • Page 5 AN0057.1: EFM32 Series 1 LCD Driver Introduction to LCD Segment Displays 2.2.1 Driving Many Segments: Static Driving An LCD display most often has more than one segment. Usually the segments are connected with one side common to many of the other segments, this is called the "common"-electrode.
  • Page 6 AN0057.1: EFM32 Series 1 LCD Driver Introduction to LCD Segment Displays Frame Start Frame End Segment 0 Segment 1 COM0 1/2V COM1 1/2V Segment 2 Segment 3 SEG0 1/2V SEG1 1/2V 1/2V Resulting Voltage SEG0-COM0 -1/2V 1/2V Resulting Voltage SEG0-COM1 -1/2V Figure 2.4.
  • Page 7 AN0057.1: EFM32 Series 1 LCD Driver EFM32 LCD Driver 3. EFM32 LCD Driver This chapter explains some of the features and possibilities of the EFM32 built-in LCD driving peripheral. For a full set of features and limitations, please see the reference manual for the specific device family.
  • Page 8 AN0057.1: EFM32 Series 1 LCD Driver EFM32 LCD Driver Selecting the correct bias is necessary to provide the waveform generator with enough voltage levels to produce the necessary wave- form for the chosen number of common lines. In general 5- to 8-plexed modes need 1/4 bias (5 voltage levels), 3- to 4-plexed modes need 1/3 bias (4 voltage levels), while 2-plexed mode needs 1/2 bias (3 voltage levels) and static mode needs only 2 voltage levels.
  • Page 9 Figure 3.2. Relative Transmission of Light Through the LCD for Changes in the Applied RMS Voltage 3.3.1 Charge Pump Mode Some LCDs require higher voltage waveforms to work. The EFM32 Series 1 LCD peripheral supports charge pump mode to generate a voltage up to twice the supply voltage of the device. V is adjusted by the LCD_DISPCTRL register CONTRAST[5:0] field.
  • Page 10 AN0057.1: EFM32 Series 1 LCD Driver EFM32 LCD Driver 3.4 Animation and Blinking The EFM32 LCD driver includes special features to enable animation and blinking of specific segments without any software interven- tion. This is useful for displaying continuous animation to signal that a device is alive, without the need to wake up from deep sleep to update the segments.

  • Page 11: Software Examples

    Note that a software example is not included for the EFM32 Series 1 Giant Gecko family because its Starter Kit (STK) does not have a liquid crystal display. The LCD peripheral does, however, have the same features, apart from segment count, so porting the example to a custom board would be trivial.
  • Page 12 AN0057.1: EFM32 Series 1 LCD Driver Software Examples 4.2 Porting the LCD Driver to other Displays This section contains a description of the necessary steps needed to port the BSP LCD driver to other displays with different segment and common line mapping. Only 4-plexed and 8-plexed displays are covered because these are the only types of displays used by EFM32 kits.
  • Page 13 AN0057.1: EFM32 Series 1 LCD Driver Software Examples Figure 4.3. EFM32 Kit LCD Glass Segments Figure 4.3 EFM32 Kit LCD Glass Segments on page 13 illustrates how the EFM32 STK LCD glass is built up. Notice the three types of segment constellations: symbols, 7-segment digits, and 14-segment alphanumerics.
  • Page 14 AN0057.1: EFM32 Series 1 LCD Driver Software Examples 4.2.2 Porting the LCD Segment Map This section is an actual step by step description of the porting. Start with selecting a kit with the same number of multiplexed common lines as your display. Either select the SLSTK3301A or SLSTK3701A.

  • Page 15: Revision History

    • Split AN0057 into AN0057.0 and AN0057.1 for MCU Series 0 and MCU Series 1 devices, respectively. • Added the 1. Device Compatibility section. • Added support for EFM32 Series 1 device EFM32TG11. • Re-organized the example code structure. Revision 1.03...
  • Page 16 Trademark Information Silicon Laboratories Inc.®, Silicon Laboratories®, Silicon Labs®, SiLabs® and the Silicon Labs logo®, Bluegiga®, Bluegiga Logo®, ClockBuilder®, CMEMS®, DSPLL®, EFM®, EFM32®, EFR, Ember®, Energy Micro, Energy Micro logo and combinations thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZRadio®, EZRadioPRO®, Gecko®, Gecko OS, Gecko OS Studio, ISOmodem®, Precision32®, ProSLIC®, Simplicity Studio®, SiPHY®, Telegesis, the Telegesis Logo®, USBXpress®...