Driving TFEL LCD Panels with RP2040: Offloading the CPU Step by Step

https://www.zephray.me/post/rpi_pico_driving_el/

by _Microft • 4 years ago

36 16 4 years ago

zephray.me

1MachineElf• 4 years ago

I appreciate the depth of this guide.

The display is gorgeous. Why aren't these more common?

mastax• 4 years ago

Expensive (this one is $700+), monochrome, fragile, dim, burn-in, high-voltage.

prvc2• 4 years ago

Why so costly?

dmitrygr2• 4 years ago

ARM SoCs from the early 2000s typically has an LCD controller that is capable of driving STN LCDs. However many of these SoCs are also being deprecated or obsolete.

STM32F4 and STM32F7 series have plenty of cheap chips that support driving STN displays

crest2• 4 years ago

Good look finding any original STM32 parts at the moment.

dmitrygr2• 4 years ago

Oh, did I miss RP2040 being ordereable in 100ku quantities?

“Sometimes available” beats “toy” anytime

crest2• 4 years ago

The code could be improved by using DMA channel chaining instead of an interrupt to reload the two DMA channels.

blacklion• 4 years ago

From source:

=== Note that it is actually possible to eliminate this interrupt as well. The PIO and DMA could push pixels out automatically without any CPU intervention. However, I am not doing it here, because precise Vsync interrupts are quite useful. I could switch framebuffers here without any tearing effects. This is also critical to implement FRC for greyscales. ===

ultrarunner• 4 years ago

This is really great. I'm struggling to find SAM D5x chips and considering swapping in RP2040s instead. Seeing the flexibility in the PIO here makes that pretty tempting.

What are people using for cheap ($5-$10/ea) displays now?

fest• 4 years ago

I use either monochrome SSD1306 based OLEDs for devices where display is more of a convenience than requirement. For nicer things, 2-3" IPS displays retail around this price, e.g. https://www.waveshare.com/2inch-lcd-module.htm

Driving TFEL LCD Panels with RP2040: Offloading the CPU Step by Step

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