PWM in nrf5340 - blinky example fails to compile with SDK 2.7.0

RE: PWM in nrf5340 - blinky example fails to compile with SDK 2.7.0

Repa — Mon, 09 Dec 2024 16:40:18 GMT

And of course that is in the alias definition:

pwm-led0 = &pwm_led0;

There must be a good reason why the build system converts the dash "-" to an underscore "_" during the build process. I really do hope there is a good reason for this.

RE: PWM in nrf5340 - blinky example fails to compile with SDK 2.7.0

Repa — Mon, 09 Dec 2024 16:28:00 GMT

When comparing with the sample there seems to be an alias definition missing in the devicetree_generated.h header:

Sample has:

/* Existence and alternate IDs: */
#define DT_N_S_pwmleds_S_pwm_led_0_EXISTS 1
#define DT_N_ALIAS_pwm_led0 DT_N_S_pwmleds_S_pwm_led_0
#define DT_N_NODELABEL_pwm_led0 DT_N_S_pwmleds_S_pwm_led_0

Whereas my the header generated from my code has:

/* Existence and alternate IDs: */
#define DT_N_S_pwmleds_S_pwm_led_0_EXISTS 1
#define DT_N_NODELABEL_pwm_led0 DT_N_S_pwmleds_S_pwm_led_0

Now just need to figure out how this alias is supposed to be generated...

RE: PWM in nrf5340 - blinky example fails to compile with SDK 2.7.0

Repa — Mon, 09 Dec 2024 13:22:22 GMT

Greetings,

thank you for the quick response!

Ok - now the sample compiles 👍

However when trying to build with custom configuration I get:

In file included from C:/Apps/NordicSemiconductor/SDKs/v2.7.0/zephyr/include/zephyr/toolchain/gcc.h:98,
                 from C:/Apps/NordicSemiconductor/SDKs/v2.7.0/zephyr/include/zephyr/toolchain.h:50,
                 from C:/Apps/NordicSemiconductor/SDKs/v2.7.0/zephyr/include/zephyr/kernel_includes.h:23,
                 from C:/Apps/NordicSemiconductor/SDKs/v2.7.0/zephyr/include/zephyr/kernel.h:17,
                 from C:/Users/mattip-local/Projects/Nordic/Sandbox/hello_world_sample/src/main.c:7:
C:/Users/mattip-local/Projects/Nordic/Sandbox/hello_world_sample/src/main.c: In function 'main':
C:/Apps/NordicSemiconductor/SDKs/v2.7.0/zephyr/include/zephyr/device.h:91:41: error: '__device_dts_ord_DT_N_ALIAS_pwm_led0_P_pwms_IDX_0_PH_ORD' undeclared (first use in this function)
   91 | #define DEVICE_NAME_GET(dev_id) _CONCAT(__device_, dev_id)

The custom board .dts file has:

/dts-v1/;
#include <nordic/nrf5340_cpuapp_qkaa.dtsi>
#include "GGHHx_Dev0_0-pinctrl.dtsi"

/ {
    model = "Custom Board auto generated by nRF Connect for VS Code (CPUAPP)";
    compatible = "None,custom-board-name-cpuapp";

    chosen {
        zephyr,console = &uart0;
        zephyr,shell-uart = &uart0;
        zephyr,uart-mcumgr = &uart0;
        zephyr,bt-mon-uart = &uart0;
        zephyr,bt-c2h-uart = &uart0;
        zephyr,sram = &sram0_image;
        zephyr,flash = &flash0;
        zephyr,code-partition = &slot0_partition;
        zephyr,sram-secure-partition = &sram0_s;
        zephyr,sram-non-secure-partition = &sram0_ns;
    };

    leds {
        compatible = "gpio-leds";
        led0: led_0 {
            gpios = <&gpio0 6 GPIO_ACTIVE_LOW>;
            label = "Green LED 0";
        };
    };

    pwmleds {
        compatible = "pwm-leds";
        pwm_led0: pwm_led_0 {
            pwms = <&sw_pwm 0 PWM_MSEC(20) PWM_POLARITY_INVERTED>;
        };
    };

};

&gpiote {
    status = "okay";
};

&gpio0 {
    status = "okay";
};

&gpio1 {
    status = "okay";
};

&pwm0 {
    status = "disabled";
};

&sw_pwm {
    status = "okay";
    channel-gpios = <&gpio0 6 PWM_POLARITY_INVERTED>;
};

What am I missing here?

RE: PWM in nrf5340 - blinky example fails to compile with SDK 2.7.0

Hieu — Mon, 09 Dec 2024 07:21:19 GMT

Hi Repa,

This line of code means that the sample expect a DeviceTree node named pwm_led0:
https://github.com/nrfconnect/sdk-zephyr/blob/v3.6.99-ncs2/samples/basic/blinky_pwm/src/main.c#L17

However, there is no such node in the bl5340_dvk board.
https://github.com/nrfconnect/sdk-zephyr/tree/v3.6.99-ncs2/boards/lairdconnect/bl5340_dvk

The sample will compile fine with the nrf5340dk/nrf5340/cpuapp target, which has such a node.
https://github.com/nrfconnect/sdk-zephyr/blob/v3.6.99-ncs2/boards/nordic/nrf5340dk/nrf5340_cpuapp_common.dtsi#L42-L47

Note that the sample is setup to overlay the nRF5340 DK board file so that the pwm_led0 device runs off of software emulated PWM rather than peripheral PWM. This is because of a specific setup in the sample.
https://github.com/nrfconnect/sdk-zephyr/commit/993cb302403634f7cbca22e0c72aebc18923eb26
The peripheral PWM works normally with a different period and duty cycle configurations.

If you need more information on DeviceTree and overlay, I recommend checking out our free online course on the basics of the nRF Connect SDK: https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/

Hieu