How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Ali Aljaani — Wed, 23 Mar 2022 07:55:31 GMT

Hi Mike,

The display driver(CONFIG_DISPLAY) https://docs.zephyrproject.org/latest/reference/display/index.html has support for the Micro:bit v2 (CONFIG_MICROBIT_DISPLAY). Try out this sample

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Øyvind — Mon, 14 Mar 2022 10:18:59 GMT

Hi Mike,

Yes, this looks correct, however, note that the bbc_microbit_v2 board files include most of what you need to use the MicroBit v2 functionality except for the pwm_led0.

The nrf_dm uses the pwm_led in led_notifcation() found under nrf\samples\bluetooth\nrf_dm\src\peer.c. When building it will complain about this LED missing, which is used to indicate the distance. You will need to configure this for your use on the MicroBit e.g. led_matrix.

-Øyvind

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Mike Wirth — Mon, 14 Mar 2022 05:29:07 GMT

Øyvind,

Many thanks. Your suggestion is right on target. I've started tp go through the DTS videos. Seem clear enough, but when I try to apply them, I still run into problems. What I'm trying to do is a mashup of the Nordic nrf_dm sample and the Zephyr nrf-led-matrix sample:

Starting with the nrf_dm sample targeted to the nRF52833 DK, I can remove the dependence on single LEDs.
Then I can change the target to bbc_microbit_v2 (which also uses the nRF52833 SOC).
At this point, I start adding code snippets from main.c in the nrf_led_matrix that use that display device.
I tried adding a dts overlay file (and changing where the alias already included in the solution that didn't point anywhere), but didn't get the details right. Seem to have gotten tangled up in aliases for device "labels".

Here's what I put in the overlay:

led_matrix: led_matrix {
		compatible = "nordic,nrf-led-matrix";
		status = "okay";
		label = "LED_MATRIX";
		width = <5>;
		height = <5>;
		pixel-mapping = [00 01 02 03 04
				 10 11 12 13 14
				 20 21 22 23 24
				 30 31 32 33 34
				 40 41 42 43 44];
		row-gpios = <&gpio0 21 GPIO_ACTIVE_HIGH>,
			    <&gpio0 22 GPIO_ACTIVE_HIGH>,
			    <&gpio0 15 GPIO_ACTIVE_HIGH>,
			    <&gpio0 24 GPIO_ACTIVE_HIGH>,
			    <&gpio0 19 GPIO_ACTIVE_HIGH>;
		col-gpios = <&gpio0 28 GPIO_ACTIVE_LOW>,
			    <&gpio0 11 GPIO_ACTIVE_LOW>,
			    <&gpio0 31 GPIO_ACTIVE_LOW>,
			    <&gpio1  5 GPIO_ACTIVE_LOW>,
			    <&gpio0 30 GPIO_ACTIVE_LOW>;
		refresh-frequency = <50>;
		timer = <&timer4>;
		pwm = <&pwm0>;
		pixel-group-size = <4>;
	};

       // pwm0: pwm0 {
		//compatible = "nordic,pwm0";
		//status = "okay";
		//label = "PWMO";
        //}

        pwm-led0: pwm0-led0 {
		compatible = "nordic,pwm0";
		status = "disabled";
		label = "PWMO";
        }

pwm0: pwm@4001c000 {
			compatible = "nordic,nrf-pwm";
			// reg = < 0x4001c000 0x1000 >;
			// interrupts = < 0x1c 0x1 >;
			status = "okay";
			label = "PWM_0";
			//#pwm-cells = < 0x1 >;
			//phandle = < 0x6 >;
                        }

Am I headed in the right general direction? Suggestions on the details? I'm headed off to look at more dts videos and docs, especially if there are any dts-related tools that help you sort out labels, devices, status, etc.

Thanks again,

Mike

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Øyvind — Fri, 11 Mar 2022 13:00:28 GMT

Hi Mike,

Yes, you seem to have encountered a Devicetree error, indicating that you have configured something incorrectly. I would recommend going through the Devicetree Guide, and have a look at this YouTube video from the Zephyr Community on the Device Model.

Can you share your project in a .zip file?

Kind regards,
Øyvind

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Mike Wirth — Wed, 09 Mar 2022 07:00:47 GMT

Øyvind,

OK, did a bit more investigation tonight. Yes, indeed, my problem is related to dts and Kconfig files. The net effect is that the following project (highlighted in yellow) is included in the zephyr sample project, nrf_led_marix, but not in my nRF sample project:

One curiosity here is that the output file for the project is named "libdrivers__display.a", not the same as the c file with an o or a extension.

As verification that this is the solution for the undefined symbol "__device_dts_ord_10" during linking, if you look at the binary inside the libdrivers__display.a, the first bit of it contains a string with the requisite symbol:

In any case, I tried to manually add this project to the solution for my nRF sample solution. (Not an SES expert.) The proper question is probably how to modify my nRF sample so that, with BBC_microbit_v2 as board, the nRF project wizard will include the nrf_led_matrix project automatically when generating the full solution.

Hope this helps,

Mike

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Mike Wirth — Tue, 08 Mar 2022 07:27:19 GMT

A bit of Google searching on the undefined reference in my prior reply leads to the following in the Zephyr docs:

DEVICE_DT_GET
...
If no such device was allocated, this will fail at linker time. If you get 
an error that looks like undefined reference to __device_dts_ord_<N>, that 
is what happened. Check to make sure your device driver is being compiled, 
usually by enabling the Kconfig options it requires.

This refers to Kconfig settings, which are part of the build files generated by the code generation wizard (I presume). How do I fix this?

Mike

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Mike Wirth — Tue, 08 Mar 2022 05:40:38 GMT

Øyvind,

Many thanks. Yes, the sample did build, compile, and load onto my Micro:Bit V2 and execute correctly (at least with lots of flashing LED patterns :-)

The critical issue for me was that I was being too restrictive in following the instructions for specifying a project in the "File → Open nRF Connect SDK Project" wizard. I was only using the triangle selector to look for available project, thus not finding "nrf_led_matrix". I didn't realize that the additional projects in the zephyr repo were available as Custom" projects and could be accessed via the normal ... file browser.

Suggestion: Perhaps the documentation in the "Toolchain Manager | First steps | Building with SEGGER Embedded Studio | 3. | Projects" could be clarified to include two facts.

The projects in the Zephyr repo are accessible as "custom" projects using the file finder.
To be considered a custom project, the project must conform to the rules proscribed in the Zephyr docs for project structure (or whatever the defining documentation is).

Remaining Problem: Having said all of this, I'm still left with a problem. Prior to receiving your reply, I went ahead and took code snippets from the Zephyr nrf_led_sample and incorporated them into one of your working samples. All went well until some calls to the display.c/h library which led to the following error:

1> Linking ‘zephyr_pre0.elf’
1> /opt/nordic/ncs/v1.9.1/toolchain/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld.bfd: app/libapp.a(main.c.obj): in function `main':
1> /opt/nordic/ncs/v1.9.1/nrf/samples/bluetooth/nrf_dm_microbit/src/main.c:473: undefined reference to `__device_dts_ord_10'

But this is triggered by code which works in the running nrf_led_matrix sample. I strongly suspect that the dts files for the bbc_microbit_v2 device are different in the nRF SDK than in the lower-level Zephyr repo. Will check this out ASAP. Or something is different in the two code generating environments.

Any suggestions?

Thanks again,

Mike

RE: How to use "nRF LED Matrix" sample and library from Zephyr with nRF Connect SDK 1.9.1 and SES for use in an app on Micro:Bit V2?

Øyvind — Mon, 07 Mar 2022 09:35:20 GMT

Hi Mike,

I opened the nRF LED Matrix sample from zephyr\samples\boards\nrf\nrf_led_matrix to use with zephyr\boards\arm\bbc_microbit_v2

And building the sample seems to work as intended as well.

I don't have the Microbit available at the moment, but assume it will work as expected.

Kind regards,
Øyvind