2.9 Featherwing 4777 example (custom lut needed?)

[damongolding]

I was hoping to do a PR to add an example of the featherwing display I have but I have bumped up against an issue with fading blacks. I have tried address the issue myself but I fear I am out of my depth now.

When using the default settings (with the added colstart=0) I see some fading/sparkling from the right (example below)

I tried using the custom lut from the magtag example, the blacks stay but the display becomes quite noisy.

Any help would be greatly appreciated.

[damongolding]

Trying a few things but still struggling.

When setting the whole display to black (via vectorio) the black remains:

On first render my display looks good:

But a starts to deteriorate straight away:

I see the same issue if I draw the battery background and line or use a background image. Strangely the line seems to "stick".

[tannewt]

Please post a picture of the label on the ribbon cable. I want to compare it to what I have.

Grayscale was definitely a bit noisy but that looks more than what I saw. I think this is what my test looked like:

[damongolding]

Please post a picture of the label on the ribbon cable. I want to compare it to what I have.

Grayscale was definitely a bit noisy but that looks more than what I saw. I think this is what my test looked like:

here you go:

Yes your images looks how I would expect mine to look.

[tannewt]

The FPC markings match mine.

I tested again with version 2.1.0 of the library and it all seems to work fine for me. I'm driving the display with the RP2040 think ink display instead of the featherwing.

I can order one to try but I won't have time to try it until next week.

[tannewt]

Looks like they are out of stock. Maybe @ladyada can test for me.

What feather are you using and what version of CircuitPython?

[ladyada]

we just put them in stock. note we're selling a version with the SSD1680. i think the new displays may be more sensitive to not being put in deep sleep (we dont do that if theres no RESET pin)

[damongolding]

Details:

K	V
MCU	ESP32-S2 feather
Display	2.9" Grayscale Featherwing (FPC-A005, SSD1680)
CircuitPython	10.0.0-beta.2

I have moved over to using the custom LUT from the MagTag example for now.

The display is a little more noisy and darker then this image portrays.

[ladyada]

grayscale is definitely noisier than it used to be. can you use the built in monochrome LUT?

[damongolding]

grayscale is definitely noisier than it used to be. can you use the built in monochrome LUT?

I assume you mean something like the below? This results in less noise but the blacks start to fade (from the right of the display). Example below.

display = adafruit_ssd1680.SSD1680(
  display_bus,
  width=WIDTH,
  height=HEIGHT,
  rotation=270,
  grayscale=False, # This doesn't seem to make any difference
  colstart=0,
  rowstart=0,
)

[ladyada]

just to check so i can reproduce: are you unplugging or depowering or going into low power mode or just running that code exactly as is

[damongolding]

The black washout? I tried running as is (with time.sleep()), unplugging, depowering (sys.exit()) but I can't remember if I tried going to low power mode.

[tannewt]

Are you giving it a busy pin? It looks like we'll go into deep sleep when the busy pin is deasserted or refresh time expires:
https://github.com/adafruit/circuitpython/blob/9238ee7d869d5fd1a2d209d1fd58ec59cf656ae5/shared-module/epaperdisplay/EPaperDisplay.c#L467-L483

Maybe the refresh time is set too long or we're failing to send the stop sequence. Note that the featherwing won't be able to wake up unfortunately because the display's reset pin is connected to the MCU reset pin.

[damongolding]

I am not currently using the busy pin. Pretty much all documentation I came across using a feather and featherwing said to set the busy and rst pin to None.

The featherwing does have a busy pad I could solder to a pin.

[tannewt]

It looks like refresh_time defaults to 40 seconds for all epaper but the grayscale config only needs 2.9 seconds (based on my busy pin connection.)

So, try adding refresh_time=3 when initing the SSD1680 object. This should send the deep sleep command sooner and disable the vcom outputs. 🤞

Something like:

display = adafruit_ssd1680.SSD1680(
    ...
    refresh_time=3
)

[damongolding]

After adding the shorter refresh_time I've seen a massive improvement.

I'm still seeing a small amount of fading. I'll continue to do more testing, this was just a quick test to see if adjusting the refresh_time made a difference.