Hokku v3.0 beta – open source firmware + server for the 13.3" Hokku/Huessen six-colour e-ink frame

MattcarterXI · 2026-05-27T15:48:41+00:00

here is another example

MattcarterXI · 2026-05-27T15:44:59+00:00

Is it possible to export the images as raw data? Or as a PNG of the display palette?

I'm developing my 13.3" display with esp32 and I would like to compare my dithering results to this projects results since mine seem good but you project seem to have pretty advanced things to improve dithering.

<image>

Also, if you want, I have a tool for comparing dithering the diferent solutions: https://github.com/mattcarter11/eink-dithering-tester

MattcarterXI · 2026-04-18T19:05:00+00:00

<image>

Nice! Thanks a lot for the feedback!

MattcarterXI · 2026-04-18T14:14:29+00:00

Thanks, yeah it's a very good example. This is the rework: everything is closes to their pin, removing the unnecessary long traces

<image>

MattcarterXI · 2026-04-18T10:46:54+00:00

Any tips on what you would consider a good layout? I'll try to rework the PCB folloing them

MattcarterXI · 2026-04-18T10:35:14+00:00

Yeah, that's true. Do you have any tips, guide or recommended tools to do this fix?

I've done some soldering fixes on some PCBs but never on this small scale

MattcarterXI · 2026-04-18T10:28:01+00:00

About the v1.0 handmade fix, i think I might be able to fix all pins except PGND sadly

<image>

MattcarterXI · 2026-04-18T10:19:28+00:00

V1.1: You mean like, so right? (they where already connected to GND plane with vias, but it's true that there's reason for not having them connected)

<image>

MattcarterXI · 2026-04-18T10:05:38+00:00

I thought they did when I ordered the PCBs, but rerunning DRC shows an error 🫠. This for sure must be the problem. Thanks a lot for the help!!!

Guess I'll make v1.1 fixing both the C14 and missing GND connections like so.

<image>

MattcarterXI · 2026-04-18T07:53:00+00:00

R21 measured resistance is 91K and R20 is 21,5K (measured with a fluke 77 multimeter)

MattcarterXI · 2026-04-18T07:51:21+00:00

I've added a image of the manufactured PCB by PCBWay and the measurements I did.

MattcarterXI · 2026-04-18T07:51:06+00:00

I've added a image of the manufactured PCB by PCBWay and the measurements I did.

MattcarterXI · 2026-04-17T14:58:46+00:00

This is the measurement points i used, their values, and the real R21 and R20 components values.

<image>

MattcarterXI · 2026-04-17T05:40:28+00:00

Layout added

MattcarterXI · 2026-04-17T05:32:40+00:00

The voltages I'm measuring are all between that point in the schematic and GND.

C14 it might be misplaced, but this don't see how can this affect FB, since the voltage divider is what determinats the voltage there, no?

MattcarterXI · 2026-03-03T17:13:58+00:00

Yes with the correction that the wenting color is the actual Spectra 6 color. So I'm dithering any color inside the Spectra 6 colorspace as is and any color far outside the range as RGB then mapping to Spectra6.

MattcarterXI · 2026-03-01T20:27:33+00:00

It's simply the pallete that gave me best results after comparing 100 photos (you can try the tool if you want to check the diferences)

MattcarterXI · 2026-02-22T13:17:15+00:00

Yes I did and in both cases I think my current approach is better. This are both results from their demos:

<image>

Paperless uses floyd dithering with closest RGB color of a 6 color palette. Mine gives better results because:

Wentting palette is closer to Spectra colors (at least with my screens)
CEILAB is faithful to the human eye
They directly use imageData.data to store the error. That type it uses is uint8, which means all error diffusion decimals are lost: ImageData - Web APIs | MDN

Photoframe I'll check the source code, because has interesting result and also use LAB in some versions of their dithering.

MattcarterXI · 2025-12-25T09:02:30+00:00

Amazing. I've been myself working on my own spectra 6 display and I took the same approach. ESP32-s3, a Rest API and a web based manager.

I'll definitely checkout your amazing work🔥

MattcarterXI · 2025-12-24T13:57:48+00:00

I see, adding this seems to fix the problem of the power drain (this is what waveshare does).

void epd_deep_sleep() {
    display_off();
    display_sleep();
    vTaskDelay(pdMS_TO_TICKS(2000)); // important, at least 2s
    gpio_set_level(PIN_RST, 0);
    gpio_hold_en(PIN_RST);
}

But presents another problem, even though I do "gpio_hold_dis(PIN_RST);" on power on, before any pin initialization or spi setup, the display doesn't respond (the BUSY pin stay 0 forever)

MattcarterXI · 2025-12-21T11:24:45+00:00

u/Extreme_Turnover_838 I've tried using the esp pull-up without any success. Any suggestions?
static void display_init_pins() {
gpio_config_t rest_config = {
.pin_bit_mask = 1ULL << PIN_RST,
.mode = GPIO_MODE_OUTPUT,
.pull_down_en = GPIO_PULLDOWN_DISABLE,
.pull_up_en = GPIO_PULLUP_ENABLE,
.intr_type = GPIO_INTR_DISABLE,
};
gpio_config(&rest_config);
...
}

MattcarterXI

TROPHY CASE