From 2b8b776b9ec554ad781cf6ed9bfebc42864fa999 Mon Sep 17 00:00:00 2001
From: Hector van der Aa <hector@h3cx.dev>
Date: Sat, 21 Mar 2026 18:03:08 +0100
Subject: [PATCH] Blue LED flash on CM4

---
 Zephyr/prj.conf   |  3 +++
 Zephyr/src/main.c | 46 +++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/Zephyr/prj.conf b/Zephyr/prj.conf
index e69de29..11ef425 100644
--- a/Zephyr/prj.conf
+++ b/Zephyr/prj.conf
@@ -0,0 +1,3 @@
+CONFIG_GPIO=y
+CONFIG_STM32H7_DUAL_CORE=y
+CONFIG_STM32H7_BOOT_M4_AT_INIT=y
diff --git a/Zephyr/src/main.c b/Zephyr/src/main.c
index 5496741..d6d67ec 100644
--- a/Zephyr/src/main.c
+++ b/Zephyr/src/main.c
@@ -1,11 +1,47 @@
-// Copyright (C) 2026 Hector van der Aa <hector@h3cx.dev>
-// Copyright (C) 2026 Association Exergie <association.exergie@gmail.com>
-// SPDX-License-Identifier: GPL-3.0-or-later
+/*
+ * Copyright (c) 2016 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
+#include <stdio.h>
+#include <zephyr/drivers/gpio.h>
 #include <zephyr/kernel.h>
-#include <zephyr/sys/printk.h>
+
+/* 1000 msec = 1 sec */
+#define SLEEP_TIME_MS 1000
+
+/* The devicetree node identifier for the "led0" alias. */
+#define LED0_NODE DT_ALIAS(led0)
+
+/*
+ * A build error on this line means your board is unsupported.
+ * See the sample documentation for information on how to fix this.
+ */
+static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(LED0_NODE, gpios);
 
 int main(void) {
-  printk("Hello from my freestanding Zephyr app!\n");
+  int ret;
+  bool led_state = true;
+
+  if (!gpio_is_ready_dt(&led)) {
+    return 0;
+  }
+
+  ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);
+  if (ret < 0) {
+    return 0;
+  }
+
+  while (1) {
+    ret = gpio_pin_toggle_dt(&led);
+    if (ret < 0) {
+      return 0;
+    }
+
+    led_state = !led_state;
+    printf("LED state: %s\n", led_state ? "ON" : "OFF");
+    k_msleep(SLEEP_TIME_MS);
+  }
   return 0;
 }