Adding additional pins to PWM channel

[Mike Austin (LPI)]

I'm trying to add addtional pins as PWM signals in my application.  I've followed the process shown here, but I'm getting a bunch of build errors.

This is my overlay file:

&pinctrl {
    pwm0_custom: pwm0_custom {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 22)>,
                    <NRF_PSEL(PWM_OUT1, 0, 23)>;
            nordic,invert;
        };
    };

    pwm0_csleep: pwm0_csleep {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 22)>,
                    <NRF_PSEL(PWM_OUT1, 0, 23)>;
            low-power-enable;
        };
    }; 
};

&pwm0 {
    status = "okay";
    pinctrl-0 = <&pwm0_custom>;
    pinctrl-1 = <&pwm0_csleep>;
    pinctrl-names = "default", "sleep";
};

/{
    pwmleds {
        compatible = "pwm-leds";
        pwm_led0: pwm_led_0 {
            pwms = <&pwm0 0 PWM_MSEC(1) PWM_POLARITY_NORMAL>;
        };
        pwm_led1: pwm_led_1 {
            pwms = <&pwm0 1 PWM_USEC(100) PWM_POLARITY_NORMAL>;
        };
    };
};

With just that, I can get my code to build without errors.

But the moment I try and get the device for the second PWM pin (pwm_led1) via:

static const struct pwm_dt_spec pwm_out_0 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led0));
static const struct pwm_dt_spec pwm_out_1 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led1));

I get all these errors:

FAILED: CMakeFiles/app.dir/src/main.c.obj 
C:\Nordic\toolchains\v2.2.0\opt\zephyr-sdk\arm-zephyr-eabi\bin\arm-zephyr-eabi-gcc.exe -DKERNEL -DNRF52832_XXAA -DUSE_PARTITION_MANAGER=0 -D__PROGRAM_START -D__ZEPHYR__=1 -IC:/Nordic/v2.2.0/zephyr/include -Izephyr/include/generated -IC:/Nordic/v2.2.0/zephyr/soc/arm/nordic_nrf/nrf52 -IC:/Nordic/v2.2.0/zephyr/soc/arm/nordic_nrf/common/. -IC:/Nordic/v2.2.0/nrf/include -IC:/Nordic/v2.2.0/nrf/tests/include -IC:/Nordic/v2.2.0/pcf85063a/include -IC:/Nordic/v2.2.0/modules/hal/cmsis/CMSIS/Core/Include -IC:/Nordic/v2.2.0/modules/hal/nordic/nrfx -IC:/Nordic/v2.2.0/modules/hal/nordic/nrfx/drivers/include -IC:/Nordic/v2.2.0/modules/hal/nordic/nrfx/mdk -IC:/Nordic/v2.2.0/zephyr/modules/hal_nordic/nrfx/. -IC:/Nordic/v2.2.0/modules/debug/segger/SEGGER -IC:/Nordic/v2.2.0/modules/debug/segger/Config -IC:/Nordic/v2.2.0/zephyr/modules/segger/. -isystem C:/Nordic/v2.2.0/zephyr/lib/libc/minimal/include -isystem c:/nordic/toolchains/v2.2.0/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.1.0/include -isystem c:/nordic/toolchains/v2.2.0/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.1.0/include-fixed -fno-strict-aliasing -Os -imacros C:/Nordic/Development/blinky_pwm/build/zephyr/include/generated/autoconf.h -ffreestanding -fno-common -g -gdwarf-4 -fdiagnostics-color=always -mcpu=cortex-m4 -mthumb -mabi=aapcs -mfp16-format=ieee --sysroot=C:/Nordic/toolchains/v2.2.0/opt/zephyr-sdk/arm-zephyr-eabi/arm-zephyr-eabi -imacros C:/Nordic/v2.2.0/zephyr/include/zephyr/toolchain/zephyr_stdint.h -Wall -Wformat -Wformat-security -Wno-format-zero-length -Wno-main -Wno-pointer-sign -Wpointer-arith -Wexpansion-to-defined -Wno-unused-but-set-variable -Werror=implicit-int -fno-pic -fno-pie -fno-asynchronous-unwind-tables -fno-reorder-functions --param=min-pagesize=0 -fno-defer-pop -fmacro-prefix-map=C:/Nordic/Development/blinky_pwm=CMAKE_SOURCE_DIR -fmacro-prefix-map=C:/Nordic/v2.2.0/zephyr=ZEPHYR_BASE -fmacro-prefix-map=C:/Nordic/v2.2.0=WEST_TOPDIR -ffunction-sections -fdata-sections -std=c99 -nostdinc -MD -MT CMakeFiles/app.dir/src/main.c.obj -MF CMakeFiles\app.dir\src\main.c.obj.d -o CMakeFiles/app.dir/src/main.c.obj -c ../src/main.c
In file included from C:\Nordic\v2.2.0\zephyr\include\zephyr\toolchain\gcc.h:88,
                 from C:\Nordic\v2.2.0\zephyr\include\zephyr\toolchain.h:50,
                 from C:\Nordic\v2.2.0\zephyr\include\zephyr\kernel_includes.h:19,
                 from C:\Nordic\v2.2.0\zephyr\include\zephyr\kernel.h:17,
                 from c:\Nordic\Development\blinky_pwm\src\main.c:12:
C:\Nordic\v2.2.0\zephyr\include\zephyr\device.h:83:41: error: '__device_dts_ord_DT_N_ALIAS_pwm_led1_P_pwms_IDX_0_PH_ORD' undeclared here (not in a function)
   83 | #define DEVICE_NAME_GET(dev_id) _CONCAT(__device_, dev_id)
      |                                         ^~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\toolchain\common.h:132:26: note: in definition of macro '_DO_CONCAT'
  132 | #define _DO_CONCAT(x, y) x ## y
      |                          ^
C:\Nordic\v2.2.0\zephyr\include\zephyr\device.h:83:33: note: in expansion of macro '_CONCAT'
   83 | #define DEVICE_NAME_GET(dev_id) _CONCAT(__device_, dev_id)
      |                                 ^~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\device.h:209:37: note: in expansion of macro 'DEVICE_NAME_GET'
  209 | #define DEVICE_DT_NAME_GET(node_id) DEVICE_NAME_GET(Z_DEVICE_DT_DEV_ID(node_id))
      |                                     ^~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\device.h:226:34: note: in expansion of macro 'DEVICE_DT_NAME_GET'
  226 | #define DEVICE_DT_GET(node_id) (&DEVICE_DT_NAME_GET(node_id))
      |                                  ^~~~~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\drivers\pwm.h:258:24: note: in expansion of macro 'DEVICE_DT_GET'
  258 |                 .dev = DEVICE_DT_GET(DT_PWMS_CTLR_BY_IDX(node_id, idx)),       \
      |                        ^~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\drivers\pwm.h:326:34: note: in expansion of macro 'PWM_DT_SPEC_GET_BY_IDX'
  326 | #define PWM_DT_SPEC_GET(node_id) PWM_DT_SPEC_GET_BY_IDX(node_id, 0)
      |                                  ^~~~~~~~~~~~~~~~~~~~~~
c:\Nordic\Development\blinky_pwm\src\main.c:50:45: note: in expansion of macro 'PWM_DT_SPEC_GET'
   50 | static const struct pwm_dt_spec pwm_out_1 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led1));
      |                                             ^~~~~~~~~~~~~~~
In file included from C:\Nordic\v2.2.0\zephyr\include\zephyr\arch\arm\aarch32\arch.h:20,
                 from C:\Nordic\v2.2.0\zephyr\include\zephyr\arch\cpu.h:19,
                 from C:\Nordic\v2.2.0\zephyr\include\zephyr\kernel_includes.h:33:
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree.h:230:32: error: 'DT_N_ALIAS_pwm_led1_P_pwms_IDX_0_VAL_channel' undeclared here (not in a function); did you mean 'DT_N_S_pwmleds_S_pwm_led_1_P_pwms_IDX_0_VAL_channel'?
  230 | #define DT_ALIAS(alias) DT_CAT(DT_N_ALIAS_, alias)
      |                                ^~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree.h:3901:9: note: in definition of macro 'DT_CAT7'
 3901 |         a1 ## a2 ## a3 ## a4 ## a5 ## a6 ## a7
      |         ^~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree\pwms.h:136:9: note: in expansion of macro 'DT_PHA_BY_IDX'
  136 |         DT_PHA_BY_IDX(node_id, pwms, idx, cell)
      |         ^~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree\pwms.h:208:9: note: in expansion of macro 'DT_PWMS_CELL_BY_IDX'
  208 |         DT_PWMS_CELL_BY_IDX(node_id, idx, channel)
      |         ^~~~~~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\drivers\pwm.h:259:28: note: in expansion of macro 'DT_PWMS_CHANNEL_BY_IDX'
  259 |                 .channel = DT_PWMS_CHANNEL_BY_IDX(node_id, idx),               \
      |                            ^~~~~~~~~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\drivers\pwm.h:326:34: note: in expansion of macro 'PWM_DT_SPEC_GET_BY_IDX'
  326 | #define PWM_DT_SPEC_GET(node_id) PWM_DT_SPEC_GET_BY_IDX(node_id, 0)
      |                                  ^~~~~~~~~~~~~~~~~~~~~~
c:\Nordic\Development\blinky_pwm\src\main.c:50:45: note: in expansion of macro 'PWM_DT_SPEC_GET'
   50 | static const struct pwm_dt_spec pwm_out_1 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led1));
      |                                             ^~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree.h:230:25: note: in expansion of macro 'DT_CAT'
  230 | #define DT_ALIAS(alias) DT_CAT(DT_N_ALIAS_, alias)
      |                         ^~~~~~
c:\Nordic\Development\blinky_pwm\src\main.c:50:61: note: in expansion of macro 'DT_ALIAS'
   50 | static const struct pwm_dt_spec pwm_out_1 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led1));
      |                                                             ^~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree.h:230:32: error: 'DT_N_ALIAS_pwm_led1_P_pwms_IDX_0_VAL_period' undeclared here (not in a function); did you mean 'DT_N_S_pwmleds_S_pwm_led_1_P_pwms_IDX_0_VAL_period'?
  230 | #define DT_ALIAS(alias) DT_CAT(DT_N_ALIAS_, alias)
      |                                ^~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree.h:3901:9: note: in definition of macro 'DT_CAT7'
 3901 |         a1 ## a2 ## a3 ## a4 ## a5 ## a6 ## a7
      |         ^~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree\pwms.h:136:9: note: in expansion of macro 'DT_PHA_BY_IDX'
  136 |         DT_PHA_BY_IDX(node_id, pwms, idx, cell)
      |         ^~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree\pwms.h:249:9: note: in expansion of macro 'DT_PWMS_CELL_BY_IDX'
  249 |         DT_PWMS_CELL_BY_IDX(node_id, idx, period)
      |         ^~~~~~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\drivers\pwm.h:260:27: note: in expansion of macro 'DT_PWMS_PERIOD_BY_IDX'
  260 |                 .period = DT_PWMS_PERIOD_BY_IDX(node_id, idx),                 \
      |                           ^~~~~~~~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\drivers\pwm.h:326:34: note: in expansion of macro 'PWM_DT_SPEC_GET_BY_IDX'
  326 | #define PWM_DT_SPEC_GET(node_id) PWM_DT_SPEC_GET_BY_IDX(node_id, 0)
      |                                  ^~~~~~~~~~~~~~~~~~~~~~
c:\Nordic\Development\blinky_pwm\src\main.c:50:45: note: in expansion of macro 'PWM_DT_SPEC_GET'
   50 | static const struct pwm_dt_spec pwm_out_1 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led1));
      |                                             ^~~~~~~~~~~~~~~
C:\Nordic\v2.2.0\zephyr\include\zephyr\devicetree.h:230:25: note: in expansion of macro 'DT_CAT'
  230 | #define DT_ALIAS(alias) DT_CAT(DT_N_ALIAS_, alias)
      |                         ^~~~~~
c:\Nordic\Development\blinky_pwm\src\main.c:50:61: note: in expansion of macro 'DT_ALIAS'
   50 | static const struct pwm_dt_spec pwm_out_1 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led1));
      |                                                             ^~~~~~~~

Note that with just the pwm_out_0 struct, everything works.  Just adding the struct for pwm_out_1 seems to give the above errors

Can anyone spot what I'm doing wrong??

Cheers,

Mike

[Amanda Hsieh]

Hi, 

Try to add aliases into overlay file for the DT_ALIAS() function:

    aliases {
		pwm-led0 = &pwm_led0;
        pwm-led1 = &pwm_led1;

	};

So the overlay file would look like this:

&pinctrl {
    pwm0_custom: pwm0_custom {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 22)>,
                    <NRF_PSEL(PWM_OUT1, 0, 23)>;
            nordic,invert;
        };
    };

    pwm0_csleep: pwm0_csleep {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 22)>,
                    <NRF_PSEL(PWM_OUT1, 0, 23)>;
            low-power-enable;
        };
    }; 
};

&pwm0 {
    status = "okay";
    pinctrl-0 = <&pwm0_custom>;
    pinctrl-1 = <&pwm0_csleep>;
    pinctrl-names = "default", "sleep";
};

/{
    pwmleds {
        compatible = "pwm-leds";
        pwm_led0: pwm_led_0 {
            pwms = <&pwm0 0 PWM_MSEC(1) PWM_POLARITY_NORMAL>;
        };
        pwm_led1: pwm_led_1 {
            pwms = <&pwm0 1 PWM_USEC(100) PWM_POLARITY_NORMAL>;
        };
    };

    aliases {
		pwm-led0 = &pwm_led0;
        pwm-led1 = &pwm_led1;

	};
};

Regards,
Amanda H.

[Mike Austin (LPI)]

Thanks Amanda.

One other thing I can't quite understand, nor find any clear explanation of, is the difference between:

1. PWM instance
2. PWM channel

And what you can and can't do with either.

If I read the specs for the nRF52832 correctly, there are 3 PWM instances (PWM0, PWM1 and PWM2) available, and then the option for up to 4 channels per instance.

And then I want to try and understand how to access different channels in the same instance, compared to, say, channel 0 in different instances.

Are there any examples, or explanations, available online that would help me understand how the PWM stuff all works?

Cheers,

Mike

[Amanda Hsieh]

Hi, 

Mike Austin (LPI) said:

If I read the specs for the nRF52832 correctly, there are 3 PWM instances (PWM0, PWM1 and PWM2) available, and then the option for up to 4 channels per instance.

That's correct and it's the answer to the first question. 

Mike Austin (LPI) said:

I want to try and understand how to access different channels in the same instance, compared to, say, channel 0 in different instances.

It depends on the pwms property of pwmleds. See this overlay and this overlay. 

The following are the PWM examples in the NCS:

PWM Blinky

PWM: RGB LED

-Amanda H.

[Mike Austin (LPI)]

Thanks Amanda.

So, just to clarify my understanding:

With this overlay file you have pwmleds assigned to PWM0, and then red_pwm_led, green_pwm_led and blue_pwm_led are assigned to channels 0, 1 and 2 respectively of PWM0.  There is then a second instance, pwmleds1, that is assigned to PWM1, and which has pwm_led1 assigned to channel 0.

I can see that PWM1 has been allocated to Pin 6, and PWM0 has been allocated to the standard PWM0 pin for the nRF52840DK, but what I don't understand is how do you allocate different channels to a pin?  Or do all the channels drive the same GPIO?  For example, where is the definition that says which pin red_pwm_led, green_pwm_led and blue_pwm_led connect to?

Regards,

Mike

[Amanda Hsieh]

Hi, 

That is an overlay file for nRF52840dongle. The PWM0 pin assigned is here https://github.com/nrfconnect/sdk-zephyr/blob/main/boards/arm/nrf52840dongle_nrf52840/nrf52840dongle_nrf52840-pinctrl.dtsi#L59-L75 

-Amanda H.