Slow 3.5″ Raspberry Pi LCD Hacked to 40 MHz with ESP8266

As microcontrollers become more and more common, we see more ways to get a lot of performance out of one chip. A great example of this was the ESP8266 which was originally seen as a cheap WiFi card but has since blossomed into its own dev platform thanks to the horsepower hidden within. To that end, [Martin] is trying to push the now-ubiquitous WiFi chip even further by rolling out his own LCD driver for it from scratch.

The display of choice is the KeDei LCD 3.5″ module which was originally intended for use with a Raspberry Pi. [Martin] points out that this display isn’t optimized for speed, but after everything is said and done he has its clock line running at 40 MHz. To get this kind of speeds from the LCD, he depopulates the first shift register and adds his own fast-propagation circuit to establish a more-traditional serial addressing mode. With use of a WLCD driver that [Martin] also wrote, it is now relatively easy to draw on the screen very quickly with an ESP module. Check it out in the video below.

If you’re looking for your own tiny, cheap, fast display, this is one cool way to do it but we would suggest spinning a carrier board for both the ESP and the added circuitry. We’re looking forward to future projects which puts devices like these inside of really tiny magic mirrors, or uses them in other places where a small graphical display would be handy.

Thanks to [Hemal] for the tip!

18 thoughts on “Slow 3.5″ Raspberry Pi LCD Hacked to 40 MHz with ESP8266

  1. Great hack!!!

    I’m my opinion nobody should buy a KeDei v6.2 screen, they’re slow as fuck and there is no open source driver, just a precompiled kernel for the Raspberry Pi 3.

    I’ve made some testing with ZDoom on a RPi3, and these are the results (7-8 fps)

    1. I was looking for a display with decent resolution/size ran by ili9341 but when going higher than 320×240, 3.2”, only ili9488 is available (unsure if esp8266 is able to hit 9488, just 9341). ili9488 driven displays are 480×320, mostly 3.95”, good estate.

  2. That’s great! I hard ordered one because it’s the cheapest 430×320 LCD with touch, by far. I was hoping to use it with a ARM Cortex M4F (Tiva C) MCU, hoping it would perform decently but I was worried that driving it by SPI would be a little slow. This should help lots!

    Ideally one would make a new controller PCB for it but it might be a pain to desolder and resolder the flex PCB (no FPC connectors on this! it’s way too cheap for that!)

    1. same here with e-paper.

      ESL/POS e-paper displays (that includes some wifi, battery, case etc) cost less than 10 bucks but are nowhere to get (if you don’t wand to buy a entire shop scale number).

        1. My friends are also wondering about this, a lot! I wish Hackaday did a special post that rounds up what different shelf/store e-paper display tech are common and what hacks have been done with them.

          1. I vote this up!!
            I too would be interested in making some projects that include an e-ink/e-paper display that didn’t have to be ripped out of something purchased with some bizarre interface that needs a reverse engineering team a year to decipher, or only available at a stupidly high price and in quantities more than a billion.
            I’m thinking high-contrast, daylight (and also torchlight) viewable, small displays that consume power only when they change… the benefits over LCD just keep stacking up (apart from speed and colour, but that depends on the end application…)

          2. The friend of mine has a friend and she said, that there are a lot of chines seller that sell those ESL e-paper thingies. But if you contact them, they try to upsell you to a store dimension size set with database computers, wireless base stations and so on. Not a single ESL e-paper thingy and if, they want zillions of those chines dollars.

            Looking through the pdfs they send it does not seem soooo difficult to build something, because it looks all a bit standard.

    2. good cheap screens are not a problem, problem is driving them
      if you are lucky to use Pee you can drive anything parallel with DPI rgb interface, from Sony psp 4.3 480×272 up to desktop 40′ fullhd panels (with panellink converter)
      then there are serial cellphone screens documented by http://andybrown.me.uk/

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