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I'm trying to use the DAC on PA4 of the STM32F4 Discovery board with Zephyr.

In order to do that, I have created the following dtoverlay file. I have tried a handful of different overlay configurations here and this is what I have landed with since it didn't appear as if any DAC was configured in the main dts file for the stm32f4_disco board:

/ {
    soc {
        dac1: dac@40007400 {
            compatible = "st,stm32-dac";
            reg = <0x40007400 0x400>;
            status = "okay";
            label = "DAC_1";
            clocks = <&rcc STM32_CLOCK_BUS_APB1 0x20000000>;
            pinctrl-0 = <&dac_out1_pa4>;
            pinctrl-names = "default";
        };
    };
};

I have also enabled the DAC in the prj.conf by adding the following:

CONFIG_DAC=y
CONFIG_DAC_STM32=y

Here is the program I'm trying to build:

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/drivers/dac.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define DAC_DEVICE_NODE DT_NODELABEL(dac1)
#define DAC_CHANNEL_ID 0 // Use DAC_OUT1 (PA4) as the output pin
#define DAC_RESOLUTION 12 // 12-bit resolution

static const struct device *const dac_dev = DEVICE_DT_GET(DAC_DEVICE_NODE);

int main(void) {

  if (!dac_dev) {
    printk("Cannot find %s!\n", DAC_DEVICE_NODE);
    return 1;
  }

  struct dac_channel_cfg channel_cfg = {
    .channel_id = DAC_CHANNEL_ID,
    .resolution = DAC_RESOLUTION,
  };


  if (dac_channel_setup(dac_dev, &channel_cfg) != 0) {
    printk("Setting up of channel %d failed!\n", DAC_CHANNEL_ID);
    return 1;
  }

  /*
   .... do something.. 
  */

  return 0;
}

However, when I build it, I get the following error:

$ west build -b stm32f4_disco -p auto
[28/40] Building C object CMakeFiles/app.dir/src/main.c.obj
FAILED: CMakeFiles/app.dir/src/main.c.obj 
ccache /home/mitch/bin/zephyr-sdk-0.16.0/arm-zephyr-eabi/bin/arm-zephyr-eabi-gcc -DCORE_CM4 -DHSE_VALUE=8000000 -DKERNEL -DSTM32F407xx -DUSE_FULL_LL_DRIVER -DUSE_HAL_DRIVER -D__PROGRAM_START -D__ZEPHYR__=1 -I/home/mitch/git/myproject/zephyr/include -I/home/mitch/git/myproject/build/zephyr/include/generated -I/home/mitch/git/myproject/zephyr/soc/arm/st_stm32/stm32f4 -I/home/mitch/git/myproject/zephyr/drivers -I/home/mitch/git/myproject/zephyr/soc/arm/st_stm32/common -I/home/mitch/git/myproject/modules/hal/cmsis/CMSIS/Core/Include -I/home/mitch/git/myproject/modules/hal/stm32/stm32cube/stm32f4xx/soc -I/home/mitch/git/myproject/modules/hal/stm32/stm32cube/stm32f4xx/drivers/include -I/home/mitch/git/myproject/modules/hal/stm32/stm32cube/stm32f4xx/drivers/include/Legacy -I/home/mitch/git/myproject/modules/hal/stm32/stm32cube/common_ll/include -isystem /home/mitch/git/myproject/zephyr/lib/libc/minimal/include -isystem /home/mitch/bin/zephyr-sdk-0.16.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/include -isystem /home/mitch/bin/zephyr-sdk-0.16.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/include-fixed -fno-strict-aliasing -Os -imacros /home/mitch/git/myproject/build/zephyr/include/generated/autoconf.h -ffreestanding -fno-common -g -gdwarf-4 -fdiagnostics-color=always -mcpu=cortex-m4 -mthumb -mabi=aapcs --sysroot=/home/mitch/bin/zephyr-sdk-0.16.0/arm-zephyr-eabi/arm-zephyr-eabi -imacros /home/mitch/git/myproject/zephyr/include/zephyr/toolchain/zephyr_stdint.h -Wall -Wformat -Wformat-security -Wno-format-zero-length -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=/home/mitch/git/myproject=CMAKE_SOURCE_DIR -fmacro-prefix-map=/home/mitch/git/myproject/zephyr=ZEPHYR_BASE -fmacro-prefix-map=/home/mitch/git/myproject=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 /home/mitch/git/myproject/src/main.c
In file included from /home/mitch/git/myproject/zephyr/include/zephyr/devicetree.h:19,
                 from /home/mitch/git/myproject/zephyr/include/zephyr/arch/arm/aarch32/arch.h:20,
                 from /home/mitch/git/myproject/zephyr/include/zephyr/arch/cpu.h:19,
                 from /home/mitch/git/myproject/zephyr/include/zephyr/kernel_includes.h:33,
                 from /home/mitch/git/myproject/zephyr/include/zephyr/kernel.h:17,
                 from /home/mitch/git/myproject/src/main.c:1:
/home/mitch/git/myproject/src/main.c: In function 'main':
/home/mitch/git/myproject/build/zephyr/include/generated/devicetree_generated.h:4816:34: error: 'DT_N_S_soc_S_dac_40007400' undeclared (first use in this function); did you mean 'DT_N_S_soc_S_dac_40007400_ORD'?
 4816 | #define DT_N_NODELABEL_dac1      DT_N_S_soc_S_dac_40007400
      |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/mitch/git/myproject/zephyr/include/zephyr/devicetree.h:4096:24: note: in expansion of macro 'DT_N_NODELABEL_dac1'
 4096 | #define DT_CAT(a1, a2) a1 ## a2
      |                        ^~
/home/mitch/git/myproject/zephyr/include/zephyr/devicetree.h:192:29: note: in expansion of macro 'DT_CAT'
  192 | #define DT_NODELABEL(label) DT_CAT(DT_N_NODELABEL_, label)
      |                             ^~~~~~
/home/mitch/git/myproject/src/main.c:13:25: note: in expansion of macro 'DT_NODELABEL'
   13 | #define DAC_DEVICE_NODE DT_NODELABEL(dac1)
      |                         ^~~~~~~~~~~~
/home/mitch/git/myproject/src/main.c:103:33: note: in expansion of macro 'DAC_DEVICE_NODE'
  103 |     printk("Cannot find %s!\n", DAC_DEVICE_NODE);
      |                                 ^~~~~~~~~~~~~~~
/home/mitch/git/myproject/build/zephyr/include/generated/devicetree_generated.h:4816:34: note: each undeclared identifier is reported only once for each function it appears in
 4816 | #define DT_N_NODELABEL_dac1      DT_N_S_soc_S_dac_40007400
      |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/mitch/git/myproject/zephyr/include/zephyr/devicetree.h:4096:24: note: in expansion of macro 'DT_N_NODELABEL_dac1'
 4096 | #define DT_CAT(a1, a2) a1 ## a2
      |                        ^~
/home/mitch/git/myproject/zephyr/include/zephyr/devicetree.h:192:29: note: in expansion of macro 'DT_CAT'
  192 | #define DT_NODELABEL(label) DT_CAT(DT_N_NODELABEL_, label)
      |                             ^~~~~~
/home/mitch/git/myproject/src/main.c:13:25: note: in expansion of macro 'DT_NODELABEL'
   13 | #define DAC_DEVICE_NODE DT_NODELABEL(dac1)
      |                         ^~~~~~~~~~~~
/home/mitch/git/myproject/src/main.c:103:33: note: in expansion of macro 'DAC_DEVICE_NODE'
  103 |     printk("Cannot find %s!\n", DAC_DEVICE_NODE);
      |                                 ^~~~~~~~~~~~~~~
ninja: build stopped: subcommand failed.
FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /home/mitch/git/myproject/build

This seems to be caused by the ability to find that device node in the the device tree binary. But I haven't been able to figure out why. The board's documentation does say that there is DAC support on PA4 and PA5.

Would appreciate any help on this. Thanks

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1 Answer 1

Reset to default
1

The problem is thatDAC_DEVICE_NODE is being used as a string when it is really a node identifier. You should use DEVICE_DT_NAME(DAC_DEVICE_NODE):

if (!dac_dev) {
    // No need to use %s since DEVICE_DT_NAME gives a string literal at compile time
    printk("Cannot find " DEVICE_DT_NAME(DAC_DEVICE_NODE) "!\n");
    return 1;
}

In fact, dac_dev cannot be NULL as it would fail to link if DEVICE_DT_GET(DAC_DEVICE_NODE) was unable to locate a valid node. You can use DEVICE_DT_GET_OR_NULL(DAC_DEVICE_NODE) if you need different behavior for some reason. See: https://docs.zephyrproject.org/apidoc/latest/group__device__model.html

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