samples: boards: renesas: Add LVD sample for Renesas

Add a simple sample using Comparator API to monitor the
voltage on Renesas boards

Signed-off-by: Quy Tran <[email protected]>

Author: quytranpzz

samples/boards/renesas/lvd/CMakeLists.txt

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+# Copyright (c) 2025 Renesas Electronics Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(lvd)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE src/main.c)

samples/boards/renesas/lvd/README.rst

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+.. zephyr:code-sample:: renesas_lvd
+   :name: Renesas Low-voltage Detection Sample using Comparator
+
+   Demonstrates monitoring and reacting to voltage levels.
+
+Overview
+********
+
+This sample application shows how to use Comparator to monitor voltage levels
+with Renesas Low-voltage Detection (LVD).
+
+Hardware Setup
+**************
+
+- Ensure that the monitored target pin is supplied with power.
+
+Building and Running
+********************
+
+To build and flash the sample on a supported Renesas RX board:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/boards/renesas/lvd
+   :board: rsk_rx130@512kb
+   :goals: build flash
+   :compact:
+
+The comparator configures trigger is rising edge. When the voltage on the monitored pin
+crosses the threshold (Vref) - defined in the board's device tree, an interrupt is generated
+and turns the LED on.

samples/boards/renesas/lvd/boards/rsk_rx130_512kb.overlay

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+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&pinctrl {
+	lvd1_default: lvd1_default {
+		group1 {
+			/* CMPA2 */
+			psels = <RX_PSEL(RX_PSEL_LVD, 14, 4)>;
+			renesas,analog-enable;
+			input-enable;
+		};
+	};
+};
+
+&lvd1 {
+	pinctrl-0 = <&lvd1_default>;
+	pinctrl-names = "default";
+	lvd-action = "maskable-interrupt";
+	voltage-level = <384>;
+	vdet-target = "cmpa";
+	lvd-trigger = "rising";
+	lvd-stabilization = <0>;
+	status = "okay";
+};

samples/boards/renesas/lvd/prj.conf

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+# Copyright (c) 2025 Renesas Electronics Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_GPIO=y
+CONFIG_COMPARATOR=y

samples/boards/renesas/lvd/sample.yaml

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+sample:
+  name: Low Voltage Detector (LVD)
+tests:
+  sample.boards.renesas.lvd:
+    platform_allow:
+      - rsk_rx130@512kb
+    tags: lvd

samples/boards/renesas/lvd/src/main.c

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+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <zephyr/drivers/comparator.h>
+#include <zephyr/drivers/gpio.h>
+#include <zephyr/kernel.h>
+#include <zephyr/sys/util.h>
+#include <zephyr/sys/printk.h>
+
+#if DT_HAS_COMPAT_STATUS_OKAY(renesas_rx_lvd)
+#define LVD_DEV DT_INST(0, renesas_rx_lvd)
+#else
+#error "Please set the correct device"
+#endif
+
+static struct gpio_dt_spec led = GPIO_DT_SPEC_GET_OR(DT_ALIAS(led0), gpios, {0});
+static const struct device *lvd_dev = DEVICE_DT_GET(LVD_DEV);
+
+#define VREF_MV (DT_PROP(LVD_DEV, voltage_level))
+
+static void lvd_callback(const struct device *dev, void *user_data)
+{
+	int ret;
+
+	printk("[WARNING] Voltage instability detected! Check power supply.\n");
+	gpio_pin_set_dt(&led, 1);
+
+	ret = comparator_get_output(lvd_dev);
+	if (ret < 0) {
+		printk("Error: failed to get comparator output\n");
+		return;
+	}
+	printk("Comparator output is %s Vref (%.2fV)\n", ret ? "ABOVE" : "BELOW",
+	       ((double)VREF_MV / 100));
+}
+
+int main(void)
+{
+	int ret;
+
+	if (!device_is_ready(lvd_dev)) {
+		printk("Comparator device not ready\n");
+		return 0;
+	}
+
+	ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);
+	if (ret != 0) {
+		printk("Error: failed to configure LED\n");
+		return -EINVAL;
+	}
+
+	gpio_pin_set_dt(&led, 0);
+
+	ret = comparator_get_output(lvd_dev);
+	if (ret < 0) {
+		printk("Error: failed to get comparator output\n");
+		return -EINVAL;
+	}
+
+	printk("Comparator output is %s Vref (%.2fV)\n", ret ? "ABOVE" : "BELOW",
+	       ((double)VREF_MV / 100));
+
+	ret = comparator_set_trigger(lvd_dev, COMPARATOR_TRIGGER_RISING_EDGE);
+	if (ret < 0) {
+		printk("Error: failed to set comparator trigger\n");
+		return -EINVAL;
+	}
+
+	ret = comparator_set_trigger_callback(lvd_dev, lvd_callback, NULL);
+	if (ret < 0) {
+		printk("Error: failed to set comparator callback\n");
+		return -EINVAL;
+	}
+
+	while (1) {
+		k_sleep(K_MSEC(100));
+	}
+}