Blue LED flash on CM4

STM32/CM7/Core/Src/main.c

@@ -122,17 +122,16 @@ int main(void) {
        /* USER CODE END Boot_Mode_Sequence_2 */
 
   /* USER CODE BEGIN SysInit */
-  if ((READ_BIT(SYSCFG->UR1, SYSCFG_UR1_BCM4))) {
-    LL_HSEM_1StepLock(HSEM, 4U);
-  } else {
-    LL_RCC_ForceCM4Boot();
-  }
   /* USER CODE END SysInit */
 
   /* Initialize all configured peripherals */
   MX_GPIO_Init();
   /* USER CODE BEGIN 2 */
-
+  if ((READ_BIT(SYSCFG->UR1, SYSCFG_UR1_BCM4))) {
+    LL_HSEM_1StepLock(HSEM, 4U);
+  } else {
+    LL_RCC_ForceCM4Boot();
+  }
   /* USER CODE END 2 */
 
   /* Infinite loop */

Zephyr/prj.conf

@@ -0,0 +1,3 @@
+CONFIG_GPIO=y
+CONFIG_STM32H7_DUAL_CORE=y
+CONFIG_STM32H7_BOOT_M4_AT_INIT=y

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;
 }