examples: add registry_core example

Author: LasseRosenow

examples/README.md

@@ -144,6 +144,7 @@ Here is a quick overview of the examples available in the RIOT:
 | [senml_saul](./advanced/senml_saul/README.md) | This example demonstrates the usage of the SAUL (Sensor Actuator Uber Layer) module with the SenML (Sensor Measurement Lists) format. |
 | [opendsme](./advanced/opendsme/README.md) | This example demonstrates the usage of the OpenDSME module in RIOT. |
 | [xipfs](./advanced/xipfs/README.md) | This example demonstrates the usage of XIPFS for creating and executing an executable file. |
+| [registry_core](./advanced/registry/registry_core/README.md) | This example demonstrates the most basic usage of the RIOT Registry. |
 
 ## Examples from Guides
 

examples/advanced/registry/registry_core/Makefile

@@ -0,0 +1,24 @@
+# name of the application
+APPLICATION = registry_example_core
+
+# If no BOARD is found in the environment, use this default:
+BOARD ?= native
+
+# This has to be the absolute path to the RIOT base directory:
+RIOTBASE ?= $(CURDIR)/../../../..
+
+# required modules
+# enable board_led schema (sys/board_led) of the riot registry
+USEMODULE += registry_namespace_sys_board_led
+# enable the ztimer to turn the led on and off every second
+USEMODULE += ztimer_msec
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+DEVELHELP ?= 1
+
+# Change this to 0 show compiler invocation lines by default:
+QUIET ?= 1
+
+include $(RIOTBASE)/Makefile.include

examples/advanced/registry/registry_core/README.md

@@ -0,0 +1,14 @@
+# Registry Core
+
+This application demonstrates the most basic usage of the RIOT Registry.
+It implements a RGB LED schema and continuously changes its value every second.
+
+## Usage
+
+Simply build and flash the application for your target board:
+
+```shell
+BOARD=YOUR_BOARD_NAME_HERE make flash term
+```
+
+Now you should see the terminal continuously print out different LED states.

examples/advanced/registry/registry_core/main.c

@@ -0,0 +1,113 @@
+/*
+ * SPDX-FileCopyrightText: 2023-2026 Lasse Rosenow <lasse.rosenow@haw-hamburg.de>
+ * SPDX-FileCopyrightText: 2023-2026 HAW Hamburg
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+/**
+ * @ingroup     examples
+ * @{
+ *
+ * @file
+ * @brief       RIOT registry core minimal example application to demonstrate
+ *              how to use the riot registry without any of its extensions.
+ *
+ * @author      Lasse Rosenow <lasse.rosenow@haw-hamburg.de>
+ *
+ * @}
+ */
+
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "periph_cpu.h"
+#include "led.h"
+#include "board.h"
+#include "registry.h"
+#include "registry/namespace/sys.h"
+#include "registry/namespace/sys/board_led.h"
+#include "ztimer.h"
+
+registry_error_t board_led_instance_apply_cb(
+    const registry_apply_cb_scope_t scope,
+    const registry_group_or_parameter_id_t *group_or_parameter_id,
+    const void *context);
+
+/* This belongs into the BOARD or Driver for example */
+registry_sys_board_led_instance_t board_led_instance_0_data = {
+    .enabled = 0,
+};
+
+registry_instance_t board_led_instance = {
+    .data = &board_led_instance_0_data,
+    .apply_cb = &board_led_instance_apply_cb,
+};
+
+/* This callback gets called, when new configurations shall be applied.
+   If interacting with configurations of drivers then this callback should be
+   implemented by the driver itself. For custom application logic, we need to
+   define this for ourselves. */
+registry_error_t board_led_instance_apply_cb(
+    const registry_apply_cb_scope_t scope,
+    const registry_group_or_parameter_id_t *group_or_parameter_id,
+    const void *context)
+{
+    (void)scope;
+    (void)context;
+
+    /* Either apply all parameters of the instance or only the given parameter.
+     * For a single LED there is no difference as it only has one parameter. */
+    if ((group_or_parameter_id == NULL) ||
+        (*group_or_parameter_id == REGISTRY_SYS_BOARD_LED_ENABLED)) {
+        /* The Driver owns the board_led data instance, so we can just get our value from there */
+        bool led_state = board_led_instance_0_data.enabled;
+        /* Turn the LED on or off depending on the led_state */
+        if (led_state == true) {
+            /* This is the apply_cb function of instance 0, so we toggle LED 0 as well */
+            LED_ON(0);
+        }
+        else {
+            LED_OFF(0);
+        }
+    }
+
+    return 0;
+}
+
+/* This belongs into our main application */
+int main(void)
+{
+    registry_init();
+
+    /* init schemas */
+    registry_add_schema_instance(&registry_sys_board_led, &board_led_instance);
+
+    bool board_led_enabled = false;
+
+    while (true) {
+        /* Invert the BOARD LED, to make it turn on and off on each subsequent cycle */
+        board_led_enabled = !board_led_enabled;
+
+        /* Create registry_node_t for the board_led_parameter */
+        const registry_node_t parameter_node = {
+            .type = REGISTRY_NODE_PARAMETER,
+            .value.parameter = {
+                .instance = &board_led_instance,
+                .parameter = &registry_sys_board_led_enabled,
+            },
+        };
+
+        /* Set new registry value */
+        registry_set(&parameter_node, &board_led_enabled, sizeof(board_led_enabled));
+
+        /* Apply the registry value to change the LED state */
+        /* (in this case calls the apply_cb function: "board_led_instance_apply_cb") */
+        registry_apply(&parameter_node);
+
+        /* Sleep for 1 second and then do it again*/
+        ztimer_sleep(ZTIMER_MSEC, 1000);
+    }
+
+    return 0;
+}