samples: drivers: dac: Add API example

# SPDX-License-Identifier: Apache-2.0

cmake_minimum_required(VERSION 3.13.1)

find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})

project(DAC)

target_sources(app PRIVATE src/main.c)

.. _dac-sample:

Digital-to-Analog Converter (DAC)

#################################

Overview

********

This sample demonstrates how to use the DAC driver API.

Building and Running

********************

The DAC output is defined in the board's devicetree and pinmux file.

Only board nucleo_l073rz is supported for now.

Sample output

=============

You should see a sawtooth signal with an amplitude of the DAC reference

voltage and a period of approx. 4 seconds at the DAC output pin specified

by the board.

The following output is printed:

.. code-block:: console

   DAC internal reference voltage: 3300 mV

   Generating sawtooth signal at DAC channel 1.

.. note:: If the DAC is not supported, the output will be an error message.

CONFIG_DAC=y

sample:

  name: DAC driver sample

tests:

  sample.drivers.dac:

    tags: DAC

    depends_on: dac

    harness: console

    harness_config:

      type: one_line

      regex:

        - "Generating sawtooth signal at DAC channel ([0-9]*)."

/*

 * Copyright (c) 2020 Libre Solar Technologies GmbH

 *

 * SPDX-License-Identifier: Apache-2.0

 */

#include <zephyr.h>

#include <sys/printk.h>

#include <drivers/dac.h>

#define DAC_DEVICE_NAME		DT_LABEL(DT_ALIAS(dac1))

#define DAC_CHANNEL_ID		1

#define DAC_RESOLUTION		12

static const struct dac_channel_cfg dac_ch_cfg = {

	.channel_id  = DAC_CHANNEL_ID,

	.resolution  = DAC_RESOLUTION

};

void main(void)

{

	struct device *dac_dev = device_get_binding(DAC_DEVICE_NAME);

	if (!dac_dev) {

		printk("Cannot get DAC device\n");

		return;

	}

	int ret = dac_channel_setup(dac_dev, &dac_ch_cfg);

	if (ret != 0) {

		printk("Setting up of DAC channel failed with code %d\n", ret);

		return;

	}

	printk("Generating sawtooth signal at DAC channel %d.\n",

		DAC_CHANNEL_ID);

	while (1) {

		/* Number of valid DAC values, e.g. 4096 for 12-bit DAC */

		const int dac_values = 1U << DAC_RESOLUTION;

		/*

		 * 1 msec sleep leads to about 4 sec signal period for 12-bit

		 * DACs. For DACs with lower resolution, sleep time needs to

		 * be increased.

		 * Make sure to sleep at least 1 msec even for future 16-bit

		 * DACs (lowering signal frequency).

		 */

		const int sleep_time = 4096 / dac_values > 0 ?

			4096 / dac_values : 1;

		for (int i = 0; i < dac_values; i++) {

			dac_write_value(dac_dev, DAC_CHANNEL_ID, i);

			k_sleep(K_MSEC(sleep_time));

		}

	}

}