tests/driver/adc: Add ADC accuracy test

# SPDX-License-Identifier: Apache-2.0

cmake_minimum_required(VERSION 3.20.0)

find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})

project(dac_accuracy)

target_sources(app PRIVATE src/main.c)

target_sources_ifdef(CONFIG_REFERENCE_VOLTAGE_TEST app PRIVATE src/ref_volt.c)

target_sources_ifdef(CONFIG_DAC_SOURCE_TEST app PRIVATE src/dac_source.c)

# Copyright (c) 2023 Intel Corporation

#

# SPDX-License-Identifier: Apache-2.0

mainmenu "ADC accuracy test"

source "Kconfig.zephyr"

# Workaround to have commas on function arguments

ZEPHYR_USER := zephyr,user

config DAC_SOURCE_TEST

	bool

	default y if $(dt_node_has_prop,/$(ZEPHYR_USER),dac)

config REFERENCE_VOLTAGE_TEST

	bool

	default y if $(dt_node_has_prop,/$(ZEPHYR_USER),reference_mv)

config NUMBER_OF_PASSES

	int "Number of passes"

	default 5

ADC accuracy test

This test checks that ADC readings match an expected value. It is

done using two approaches:

 - DAC source: a board DAC pin is set to a known value, which is then

 read on an ADC one. If they match, the test passes.

 - Reference voltage: an ADC channel is read and compared to an expected

 value.

For the DAC source, it is expected that DAC and ADC are connected. This

can be indicated for twister runs by setting the fixture "dac_adc_loop".

The test then sets DAC to half its resolution and reads the ADC to see

if they match. Note that DAC and ADC are expected to generate/read

voltage on the same range.

In the reference voltage case, the ADC is expected to be connected to a

known voltage reference, whose value is informed, in millivolts, at

property "reference_mv" from "zephyr,user" node. The test reads the ADC

to see if they match.

CONFIG_DAC=y

/*

 * Copyright (c) 2023 Intel Corporation

 *

 * SPDX-License-Identifier: Apache-2.0

 */

/* Please connect J4.3 and J4.11 together to run this test.

 * J4.3 will be the ADC input and J4.11 the DAC output

 */

/ {

	zephyr,user {

		io-channels = <&adc0 20>;

		dac = <&dac0>;

		dac-channel-id = <0>;

		dac-resolution = <12>;

	};

};

&adc0{

	#address-cells = <1>;

	#size-cells = <0>;

	status = "okay";

	channel@14 {

		reg = <20>;

		zephyr,gain = "ADC_GAIN_1";

		zephyr,reference = "ADC_REF_INTERNAL";

		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;

		zephyr,resolution = <12>;

	};

};