Waveshare e-paper display, spi, zephyr, nrf52840dk

RE: Waveshare e-paper display, spi, zephyr, nrf52840dk

mej7000 — Thu, 30 May 2024 15:44:36 GMT

Yes, I agree. I have both the fundamentals and intermediate certifications and they are really helpful in understanding the concepts. Still have so much more to learn, but in this case it's more the specifics of the implementation that is causing us issue.

Also, DSHIELD is new to us and I don't remember that being covered in the certifications. It appears that DSHIELD is responsible for creating an overlay for the Waveshare display...?

RE: Waveshare e-paper display, spi, zephyr, nrf52840dk

mej7000 — Thu, 30 May 2024 15:40:18 GMT

This morning we connected the Waveshare to an Arduino Uno and it worked immediately, so we know the display is good. We bought this one from Amazon:

https://www.amazon.com/dp/B07Z1WYRQH?psc=1&ref=ppx_yo2ov_dt_b_product_details

And we've been using this DSHIELD, although we can't seem to find in the Waveshare specs exactly what Controller the hardware uses (FPC A002 printed on ribbon cable):

west build -b nrf52840dk_nrf52840 -d build52840 -- -DSHIELD=waveshare_epaper_gdeh0213b1

our display is 250x122 and the shield seems to generate, something compatible (as far as I can tell)

width = <250>;

height = <120>;

Everything compiles without issue, but I was hoping you could give us more insight. We believe the sample uses SPI3 and the following pinout, but we get nothing on the screen...

nrf52840dk (default SPI3):

MISO (NC)
MOSI P1.13
SCK P1.15
CS P1.12

Waveshare Overlay:

DC P1.11
RESET P1.10
BUSY P1.08

Am I missing something obvious? Any insight is appreciated.

thanks, mike

devzone.nordicsemi.com/.../Zephyr_5F00_ePaper_5F00_Demo.zip

RE: Waveshare e-paper display, spi, zephyr, nrf52840dk

Jenwhiz — Tue, 28 May 2024 13:56:01 GMT

Hi, would you be able to confirm what pins you used to make this work. I used the D9-7 as specified in the waveshare_epaper_gdeh0213b1.overlay file for reset dc and busy. I added an overlay for the SPI pins, but can't seem to get them to work.

RE: Waveshare e-paper display, spi, zephyr, nrf52840dk

AHaug — Fri, 24 May 2024 12:20:48 GMT

Hi,

[quote user="mej7000"]
Can you confirm what SPI pins to use?[/quote]

Regarding the SPI pins, you can use any free available gpio pin (consult with the PS for the 52840DK to see which GPIOs are not in use by default, which are used by some peripherals i.e not free to use without disabling something else) and the board files for the nRF52840dk located in <ncs_installation>zephyr/boards/nordic/nrf52840dk_nrf52840.dts can be used to verify how it is set up by default.

[quote user="mej7000"] It looks like both SPI1 and SPI3 are enabled by default on the 52840dk[/quote]

The SPI definitions enabled by default on the 52840DK can be seen here: https://github.com/nrfconnect/sdk-zephyr/blob/41095df79d11e081ea96d150fbe3dbd93f73af6c/boards/nordic/nrf52840dk/nrf52840dk_nrf52840.dts#L206C1-L304C3, which includes those instances of the peripheral you mention.

If you wish to change which GPIOs the SPI instances should use, you can change them using an overlay file as explained in lesson 2 of the fundamentals course and showcased how it's used in the intermediate course (There is also a dedicated SPI course in lesson 5)

[quote user="mej7000"]I don't see a custom device tree in your sample for the nrf52840, so I imagine it's one of these default SPI definitions?[/quote]

Helmut can probably answer this themselves as well, but in general yes, this is the case. Unless you have modified the board file directly, meaning that you've modified "a SDK file" and not a "project-dedicated board file" and there are no existing overlay files, then it is the default board file that is the one being used

I strongly recommend you having a look at both the fundamentals and intermediate course to get a head start on your project using NCS/Zephyr in addition to the sample Helmut has created

Kind regards,
Andreas

RE: Waveshare e-paper display, spi, zephyr, nrf52840dk

mej7000 — Fri, 24 May 2024 12:06:54 GMT

Hi Helmut, Thanks for your reply!

Can you confirm what SPI pins to use? It looks like both SPI1 and SPI3 are enabled by default on the 52840dk. I don't see a custom device tree in your sample for the nrf52840, so I imagine it's one of these default SPI definitions?

btw, this is the Waveshare device I was able to source quickly if you have any additional insights:
https://www.amazon.com/dp/B07Z1WYRQH?psc=1&ref=ppx_yo2ov_dt_b_product_details

RE: Waveshare e-paper display, spi, zephyr, nrf52840dk

khelmutlord — Mon, 20 May 2024 15:08:29 GMT

Hey Michael,

I've created this demo for the WaveShare epaper hat. This uses LVGL and the display subsystem in Zephyr and cycles between a couple of different QR codes. You could also use the basic LVGL demo in Zephyr but it may update too often for your display.

https://github.com/hlord2000/Zephyr_ePaper_Demo

Note that you will need to add a "shield" that specifies which display (and thus which controller IC) is being used:

https://docs.zephyrproject.org/latest/boards/shields/waveshare_epaper/doc/index.html

Thanks,

Helmut Lord