What makes the LCD controllers (K3x) special?

[paulkafig]

I'm just starting to learn about this family of processors, so this might sound like a "dumb" question. I'm trying to understand what makes the K3x family of processor so special when it comes to using it as an LCD controller? Why not use another general purpose micro?

Thank you.

[mjbcswitzerland]

Hi Paul

See chapter 2 of http://www.utasker.com/docs/uTasker/uTasker_SLCD.pdf

The SLCD controller needs to generate multiple voltages and multiplex many segments - it can be done with any processor using external HW to control the voltages but this adds HW, requires that the processor continuously updates the mux lines in software and doesn't allow the processor to sleep (as is possible with SLCD controller doing the work). SLCD devices are usually very low power and so needing the processor to always run would make the design very in efficient in terms of power consumption and also in terms of SW load to simply hold a static display.

Regards

Mark
Kinetis for professionals: http://www.utasker.com/kinetis.html

P.S. See also the video: https://www.youtube.com/watch?v=nm2DmZv1rj8

[paulkafig]

Thanks, Mark. This is helpful ☺

If I can ask a follow-up…

I see how this works well for SLCDs. What if I’m driving segmented LEDs instead? Is there a way to use the built-in engine for segmented components and do the voltage boosting (if necessary) externally? For example, if the LEDs require 5V instead of 3.3.

Best regards,

Paul

[mjbcswitzerland]

Paul

The SLCD controller in the K3x and K4x parts is designed for driving SLCDs and are not suitable for segment LEDs.

Segment LEDs don't need multiplexing/refreshing (although it - or PWM - can be used to control the brightness) and general purpose I/Os are usually suitable. You can also think about using a 5V part (such as the KE series) to simplifying interfacing to 5V LEDs.

Regards

Mark

[paulkafig]

Got it. Thanks for the help.