Utilizing waveshare e-paper display on nRF52840 dongle with Zephyr RTOS

[xiancong]

Hi Sir/Mdm, 

I want to use 1.54 inch e-paper module from waveshare with nRF52840 dongle with Zephyr RTOS.

I have read the documentation from Zephyr about the display and noticed that the display can only be used with a board that provides a configuration for Arduino connectors and defines node aliases for SPI and GPIO interfaces (see Shields for more details). 

However, based on the board configuration code provided by zephyr in nrf52840dongle_nrf52840.dts, it doesn't come with a configuration for Arduino connectors like in nrf52840dk_nrf52840.dts did. 

Hence, I added

 

arduino_header: connector {
		compatible = "arduino-header-r3";
		#gpio-cells = <2>;
		gpio-map-mask = <0xffffffff 0xffffffc0>;
		gpio-map-pass-thru = <0 0x3f>;
		gpio-map = <0 0 &gpio0 3 0>,	/* A0 */
			   <1 0 &gpio0 4 0>,	/* A1 */
			   <2 0 &gpio0 28 0>,	/* A2 */
			   <3 0 &gpio0 29 0>,	/* A3 */
			   <4 0 &gpio0 30 0>,	/* A4 */
			   <5 0 &gpio0 31 0>,	/* A5 */
			   <6 0 &gpio1 1 0>,	/* D0 */
			   <7 0 &gpio1 2 0>,	/* D1 */
			   <8 0 &gpio1 3 0>,	/* D2 */
			   <9 0 &gpio1 4 0>,	/* D3 */
			   <10 0 &gpio1 5 0>,	/* D4 */
			   <11 0 &gpio1 6 0>,	/* D5 */
			   <12 0 &gpio1 7 0>,	/* D6 */
			   <13 0 &gpio1 8 0>,	/* D7 */
			   <14 0 &gpio1 10 0>,	/* D8 */
			   <15 0 &gpio1 11 0>,	/* D9 */
			   <16 0 &gpio1 12 0>,	/* D10 */
			   <17 0 &gpio1 13 0>,	/* D11 */
			   <18 0 &gpio1 14 0>,	/* D12 */
			   <19 0 &gpio1 15 0>,	/* D13 */
			   <20 0 &gpio0 26 0>,	/* D14 */
			   <21 0 &gpio0 27 0>;	/* D15 */
	};

and 

arduino_spi: &spi3 {
	status = "okay";
	sck-pin = <47>;
	miso-pin = <46>;
	mosi-pin = <45>;
	cs-gpios = <&arduino_header 16 GPIO_ACTIVE_LOW>; /* D10 */
};

into the nrf52840dongle_nrf52840.dts file and it does build without giving an error. 

These are the pins config in the waveshare_epaper.overlay file I'm supposed to connect:

E-paper display Pins	Arduino Pins	nRF52840 dongle Pins
Vcc	5V	5V
GND	GND	GND
DIN	D11	P1.13
CLK	D13	P1.15
CS	D10	P1.12
DC	D9	P1.11
RST	D8	P1.10
BUSY	D7	P1.08

The problem I'm facing is there are only a few pins on the dongle that I could connect them directly, hence I'll need to do some configuration. 

These are the steps that I tried and it didn't work out:
1. I tried matching the original pins (which directly copied from nrf52840dk.overlay) without changing anything but it didn't work because there are only 5 matching pins (including analog pins).

2. I tried with the analog pins cuz there are there are P0.29 and P0.31 match with the dongle and still couldn't work. 

3. I tried changing the gpio to match with the pins on the dongle as the example below which I changed the D7, D9 and D10 to P0.xx and it still didn't display anything.

	arduino_header: connector {
		compatible = "arduino-header-r3";
		#gpio-cells = <2>;
		gpio-map-mask = <0xffffffff 0xffffffc0>;
		gpio-map-pass-thru = <0 0x3f>;
		gpio-map = <0 0 &gpio0 3 0>,	/* A0 */
			   <1 0 &gpio0 4 0>,	/* A1 */
			   <2 0 &gpio0 28 0>,	/* A2 */
			   <3 0 &gpio0 29 0>,	/* A3 */
			   <4 0 &gpio0 30 0>,	/* A4 */
			   <5 0 &gpio0 31 0>,	/* A5 */
			   <6 0 &gpio1 1 0>,	/* D0 */
			   <7 0 &gpio1 2 0>,	/* D1 */
			   <8 0 &gpio1 3 0>,	/* D2 */
			   <9 0 &gpio1 4 0>,	/* D3 */
			   <10 0 &gpio1 5 0>,	/* D4 */
			   <11 0 &gpio1 6 0>,	/* D5 */
			   <12 0 &gpio1 7 0>,	/* D6 */
			   <13 0 &gpio0 24 0>,	/* D7 */
			   <14 0 &gpio1 10 0>,	/* D8 */
			   <15 0 &gpio0 20 0>,	/* D9 */
			   <16 0 &gpio0 22 0>,	/* D10 */
			   <17 0 &gpio1 13 0>,	/* D11 */
			   <18 0 &gpio1 14 0>,	/* D12 */
			   <19 0 &gpio1 15 0>,	/* D13 */
			   <20 0 &gpio0 26 0>,	/* D14 */
			   <21 0 &gpio0 27 0>;	/* D15 */
};

4. I tried changing to different digital pins in the epaper.overlay file and didn't manage to get it work as well. 

5. I also couldn't find much things related to arduino pins configuration for the nRF52840 dongle.

This is my github repo for the current project. 
Please do provide suggestions and solutions that I can try out for this.

Thanks and Regards,
Xian Cong.

[Øivind]

Hi, sorry for the late reply

By default, the available pins along the edges of the dongle seem to be:

P0.02
P0.09
P0.10
P0.13
P0.15
P0.29
P1.00
P1.10
P1.15

Try only using these pins, and see if that works.

[xiancong]

Hi, 

Thanks for your reply. I have found the problem that causes it to not work. 

The documentation from Zephyr about the display is actually referring to this driver while I'm using the 1.54-inch e-paper module. The driver comes with a micro SD slot while the module I'm using isn't, hence it's not working. 

Currently, I have found the driver file for the module I'm using but it's for Arduino. I wanted to convert it to Zephyr compatible by changing some of the language references (e.g. digitalWrite, digitalRead...) but I'm not very familiar with Zephyr. May I know if there are any references that I can refer to convert the drivers to be Zephyr compatible? I believe I'll only need to change the .cpp files to make them compatible. 

Thanks and regards,
Xian Cong.

[Øivind]

This site has a lot of information about the zephyr devicetree, and how to write drivers for zephyr, the pages in the sidebar about devicetree and drivers would be relevant to read:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.6.1/zephyr/guides/dts/howtos.html#write-device-drivers-using-devicetree-apis

There are many other posts about creating zephyr drivers if you search here on devzone or the internet.

I also found this, which is for the old nrf5 sdk, but might still be useful for some inspiration:

https://gitlab.com/hooeezit/waveshare-epaper-nrf52-dk-demo

[xiancong]

Hi, 

Sorry for the late reply, the links provided are very useful. Thanks a lot for your help!

Regards,
Xian Cong.