test: adc: voltage divider

adds tests for the voltage divider binding macro and rescaling function.

Signed-off-by: Jason Yuan <jasonyuan@google.com>

tests/drivers/adc/adc_rescale/CMakeLists.txt

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+# Copyright 2023 The ChromiumOS Authors
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(adc_rescale)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/drivers/adc/adc_rescale/boards/native_posix.overlay

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+/*
+ * Copyright 2023 The ChromiumOS Authors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+ #include <zephyr/dt-bindings/adc/adc.h>
+
+/ {
+	sensor0: vd {
+		compatible = "voltage-divider";
+		io-channels = <&adc0 0>;
+		output-ohms = <50>;
+		full-ohms = <100>;
+	};
+
+	adc0: adc {
+		compatible = "zephyr,adc-emul";
+		nchannels = <2>;
+		ref-internal-mv = <3300>;
+		ref-external1-mv = <5000>;
+		#io-channel-cells = <1>;
+		status = "okay";
+	};
+};
+
+&adc0 {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,vref-mv = <3300>;
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+	};
+};

tests/drivers/adc/adc_rescale/boards/native_posix_64.overlay

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+/*
+ * Copyright 2023 The ChromiumOS Authors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include "native_posix.overlay"

tests/drivers/adc/adc_rescale/prj.conf

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+CONFIG_ZTEST=y
+CONFIG_ZTEST_NEW_API=y
+
+CONFIG_ADC=y
+CONFIG_ADC_LOG_LEVEL_INF=y
+CONFIG_HEAP_MEM_POOL_SIZE=1024
+CONFIG_TEST_USERSPACE=y

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

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+/*
+ * Copyright (c) 2023 The ChromiumOS Authors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/adc.h>
+#include <zephyr/drivers/adc/adc_emul.h>
+#include <zephyr/drivers/adc/voltage_divider.h>
+#include <zephyr/kernel.h>
+#include <zephyr/ztest.h>
+
+/* Raw to millivolt conversion doesn't handle rounding */
+#define MV_OUTPUT_EPS 10
+
+#define ADC_TEST_NODE_0 DT_NODELABEL(sensor0)
+
+/**
+ * @brief Get ADC emulated device
+ *
+ * @return pointer to ADC device
+ */
+const struct device *get_adc_device(void)
+{
+	const struct device *const adc_dev = DEVICE_DT_GET(DT_NODELABEL(adc0));
+
+	zassert_true(device_is_ready(adc_dev), "ADC device is not ready");
+
+	return adc_dev;
+}
+
+static int init_adc(const struct adc_dt_spec *spec, int input_mv)
+{
+	int ret;
+
+	zassert_true(device_is_ready(spec->dev), "ADC device is not ready");
+
+	ret = adc_channel_setup_dt(spec);
+	zassert_equal(ret, 0, "Setting up of the first channel failed with code %d", ret);
+
+	/* ADC emulator-specific setup */
+	ret = adc_emul_const_value_set(spec->dev, spec->channel_id, input_mv);
+	zassert_ok(ret, "adc_emul_const_value_set() failed with code %d", ret);
+
+	return ret;
+}
+
+/*
+ * test_adc_voltage_divider
+ */
+static int test_task_voltage_divider(void)
+{
+	int ret;
+	int32_t calculated_voltage = 0;
+	int32_t input_mv = 1000;
+	const struct voltage_divider_dt_spec adc_node_0 =
+		VOLTAGE_DIVIDER_DT_SPEC_GET(ADC_TEST_NODE_0);
+
+	ret = init_adc(&adc_node_0.port, input_mv);
+	zassert_equal(ret, 0, "Setting up of the first channel failed with code %d", ret);
+
+	struct adc_sequence sequence = {
+		.buffer = &calculated_voltage,
+		.buffer_size = sizeof(calculated_voltage),
+	};
+	adc_sequence_init_dt(&adc_node_0.port, &sequence);
+
+	ret = adc_read(adc_node_0.port.dev, &sequence);
+	zassert_equal(ret, 0, "adc_read() failed with code %d", ret);
+
+	ret = adc_raw_to_millivolts_dt(&adc_node_0.port, &calculated_voltage);
+	zassert_equal(ret, 0, "adc_raw_to_millivolts_dt() failed with code %d", ret);
+
+	ret = voltage_divider_scale_dt(&adc_node_0, &calculated_voltage);
+	zassert_equal(ret, 0, "divider_scale_voltage_dt() failed with code %d", ret);
+
+	zassert_within(calculated_voltage, input_mv * 2, MV_OUTPUT_EPS,
+		       "%u != %u should have set value", calculated_voltage, input_mv * 2);
+
+	return TC_PASS;
+}
+
+ZTEST_USER(adc_rescale, test_adc_voltage_divider)
+{
+	zassert_true(test_task_voltage_divider() == TC_PASS);
+}
+
+void *adc_rescale_setup(void)
+{
+	k_object_access_grant(get_adc_device(), k_current_get());
+
+	return NULL;
+}
+
+ZTEST_SUITE(adc_rescale, NULL, adc_rescale_setup, NULL, NULL, NULL);

tests/drivers/adc/adc_rescale/testcase.yaml

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+common:
+  tags: adc drivers userspace
+tests:
+  drivers.adc.rescale:
+    depends_on: adc
+    platform_allow: native_posix