tests/driver/adc: Add ADC accuracy test

These tests, that expects boards to be properly setup, allow one to
measure ADC value and compare to expected values.

Two tests are added. For one, a reference voltage is expected on the ADC
- and this value can be informed to the test via devicetree. The other
uses DAC to generate a value that is then read from ADC. This assumes
DAC is accurate. Naturally, one could make this a DAC test if ADC is
assumed to be accurate.

As the board setup involve connecting physical pins, they are behind
twister fixtures.

Signed-off-by: Yusuf Ahmed <muhammed.ahmed@intel.com>
Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>

tests/drivers/adc/adc_accuracy_test/CMakeLists.txt

@@ -0,0 +1,10 @@
+# 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)

tests/drivers/adc/adc_accuracy_test/Kconfig

@@ -0,0 +1,22 @@
+# 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

tests/drivers/adc/adc_accuracy_test/README.txt

@@ -0,0 +1,21 @@
+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.

tests/drivers/adc/adc_accuracy_test/boards/frdm_k64f.conf

@@ -0,0 +1 @@
+CONFIG_DAC=y

tests/drivers/adc/adc_accuracy_test/boards/frdm_k64f.overlay

@@ -0,0 +1,32 @@
+/*
+ * 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>;
+	};
+};

tests/drivers/adc/adc_accuracy_test/boards/frdm_kl25z.overlay

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2023 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 12>;
+		reference_mv = <1100>;
+	};
+};
+
+&adc0{
+	#address-cells = <1>;
+	#size-cells = <0>;
+	status = "okay";
+
+	channel@12 {
+		reg = <12>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+	};
+};

tests/drivers/adc/adc_accuracy_test/prj.conf

@@ -0,0 +1,2 @@
+CONFIG_ZTEST=y
+CONFIG_ADC=y

tests/drivers/adc/adc_accuracy_test/src/dac_source.c

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2023 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/adc.h>
+#include <zephyr/drivers/dac.h>
+#include <zephyr/drivers/adc.h>
+#include <zephyr/ztest.h>
+
+#define DIV 2
+
+#define DAC_DEVICE_NODE	DT_PROP(DT_PATH(zephyr_user), dac)
+
+extern const struct adc_dt_spec *get_adc_channel(void);
+
+static const struct dac_channel_cfg dac_ch_cfg = {
+	.channel_id = DT_PROP(DT_PATH(zephyr_user), dac_channel_id),
+	.resolution = DT_PROP(DT_PATH(zephyr_user), dac_resolution),
+	.buffered = true
+};
+
+static const struct device *init_dac(void)
+{
+	int ret;
+	const struct device *const dac_dev = DEVICE_DT_GET(DAC_DEVICE_NODE);
+
+	zassert_true(device_is_ready(dac_dev), "DAC device is not ready");
+
+	ret = dac_channel_setup(dac_dev, &dac_ch_cfg);
+	zassert_equal(ret, 0,
+		      "Setting up of the first channel failed with code %d", ret);
+
+	return dac_dev;
+}
+
+static int test_dac_to_adc(void)
+{
+	int ret, write_val;
+	int32_t sample_buffer = 0;
+
+	struct adc_sequence sequence = {
+		.buffer      = &sample_buffer,
+		.buffer_size = sizeof(sample_buffer),
+	};
+
+	const struct device *dac_dev = init_dac();
+	const struct adc_dt_spec *adc_channel = get_adc_channel();
+
+	write_val = (1U << dac_ch_cfg.resolution) / DIV;
+
+	ret = dac_write_value(dac_dev, DT_PROP(DT_PATH(zephyr_user), dac_channel_id), write_val);
+
+	zassert_equal(ret, 0, "dac_write_value() failed with code %d", ret);
+
+	k_sleep(K_MSEC(10));
+
+	adc_sequence_init_dt(adc_channel, &sequence);
+	ret = adc_read_dt(adc_channel, &sequence);
+
+	zassert_equal(ret, 0, "adc_read_dt() failed with code %d", ret);
+	zassert_within(sample_buffer,
+			(1U << adc_channel->resolution) / DIV, 32,
+			"Value %d read from ADC does not match expected range.",
+			sample_buffer);
+
+	return TC_PASS;
+}
+
+ZTEST(adc_accuracy_test, test_dac_to_adc)
+{
+	int i;
+
+	for (i = 0; i < CONFIG_NUMBER_OF_PASSES; i++) {
+		zassert_true(test_dac_to_adc() == TC_PASS);
+	}
+}

tests/drivers/adc/adc_accuracy_test/src/main.c

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2023 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/adc.h>
+#include <zephyr/ztest.h>
+
+#if DT_NODE_HAS_PROP(DT_PATH(zephyr_user), io_channels)
+static const struct adc_dt_spec adc_channel = ADC_DT_SPEC_GET(DT_PATH(zephyr_user));
+#else
+#error "Unsupported board."
+#endif
+
+const struct adc_dt_spec *get_adc_channel(void)
+{
+	return &adc_channel;
+}
+
+static void *adc_setup(void)
+{
+	int ret;
+
+	zassert_true(adc_is_ready_dt(&adc_channel), "ADC device is not ready");
+	ret = adc_channel_setup_dt(&adc_channel);
+	zassert_equal(ret, 0,
+		"Setting up of the ADC channel failed with code %d", ret);
+
+	return NULL;
+}
+
+ZTEST_SUITE(adc_accuracy_test, NULL, adc_setup, NULL, NULL, NULL);

tests/drivers/adc/adc_accuracy_test/src/ref_volt.c

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2023 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/adc.h>
+#include <zephyr/ztest.h>
+
+#define REF_V DT_PROP(DT_PATH(zephyr_user), reference_mv)
+
+extern const struct adc_dt_spec *get_adc_channel(void);
+
+static int test_ref_to_adc(void)
+{
+	int ret;
+	int32_t sample_buffer = 0;
+
+	struct adc_sequence sequence = {
+		.buffer      = &sample_buffer,
+		.buffer_size = sizeof(sample_buffer),
+	};
+
+	const struct adc_dt_spec *adc_channel = get_adc_channel();
+
+	adc_sequence_init_dt(adc_channel, &sequence);
+
+	ret = adc_read_dt(adc_channel, &sequence);
+	zassert_equal(ret, 0, "adc_read_dt() failed with code %d", ret);
+
+	ret = adc_raw_to_millivolts_dt(adc_channel, &sample_buffer);
+	zassert_equal(ret, 0, "adc_raw_to_millivolts_dt() failed with code %d",
+		      ret);
+	zassert_within(sample_buffer, REF_V, 32,
+		"Value %d mV read from ADC does not match expected range (%d mV).",
+		sample_buffer, REF_V);
+
+	return TC_PASS;
+}
+
+ZTEST(adc_accuracy_test, test_ref_to_adc)
+{
+	int i;
+
+	for (i = 0; i < CONFIG_NUMBER_OF_PASSES; i++) {
+		zassert_true(test_ref_to_adc() == TC_PASS);
+	}
+}

tests/drivers/adc/adc_accuracy_test/testcase.yaml

@@ -0,0 +1,19 @@
+common:
+  tags:
+    - adc
+    - drivers
+  depends_on:
+    - adc
+tests:
+  drivers.adc.accuracy.dac_source:
+    depends_on:
+      - dac
+    harness_config:
+      fixture: dac_adc_loopback
+    platform_allow:
+      - frdm_k64f
+  drivers.adc.accuracy.ref_volt:
+    harness_config:
+      fixture: adc_ref_volt
+    platform_allow:
+      - frdm_kl25z