modules: Add piping for decoding incoming CBOR shadow data

Add piping for decoding incoming CBOR shadow data
Fix use of json payload channel

Signed-off-by: Simen S. Røstad <simen.rostad@nordicsemi.no>

Author: simensrostad

app/CMakeLists.txt

@@ -21,6 +21,7 @@ add_subdirectory(src/modules/cloud)
 add_subdirectory(src/modules/location)
 add_subdirectory(src/modules/fota)
 add_subdirectory(src/modules/button)
+add_subdirectory(src/cbor)
 
 # Optional modules
 add_subdirectory_ifdef(CONFIG_APP_POWER src/modules/power)

app/src/Kconfig.main

@@ -16,10 +16,6 @@ config APP_MODULE_THREAD_STACK_SIZE
 	int "Thread stack size"
 	default 3200
 
-config APP_MODULE_RECV_BUFFER_SIZE
-	int "Receive buffer size"
-	default 1024
-
 config APP_REQUEST_NETWORK_QUALITY
 	bool "Request network quality"
 	help

app/src/cbor/CMakeLists.txt

@@ -0,0 +1,8 @@
+#
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+target_sources(app PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/cbor_helper.c)
+target_include_directories(app PRIVATE .)

app/src/cbor/cbor_helper.c

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#include <zephyr/logging/log.h>
+#include <zcbor_decode.h>
+
+LOG_MODULE_DECLARE(main, CONFIG_APP_LOG_LEVEL);
+
+int get_update_interval_from_cbor_response(const uint8_t *cbor,
+		       size_t len,
+		       uint64_t *interval_sec)
+{
+	*interval_sec = 60;
+	return 0;
+}

app/src/cbor/cbor_helper.h

@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#include <zephyr/types.h>
+
+int get_update_interval_from_cbor_response(const uint8_t *cbor,
+					   size_t len,
+					   uint64_t *interval_sec);

app/src/cbor/device_shadow.cddl

@@ -0,0 +1,53 @@
+; Define the basic structure of the JSON object
+
+; The 'any' type is used in this schema to allow forward compatibility.
+; They are inserted into maps that may contain additional fields in the future.
+; This prevents cbor decoding from failing in the field when the cloud side has new fields.
+app-object = {
+    ? "nrfcloud_mqtt_topic_prefix": tstr,
+    ? "pairing": pairing-type,
+    ? "lwm2m": lwm2m-map,
+    * tstr => any
+}
+
+; Define the pairing object with nested topics
+pairing-type = {
+    "state": tstr,
+    "topics": {
+        "d2c": tstr,
+        "c2d": tstr,
+        * tstr => any
+    },
+    * any => any
+}
+
+lwm2m-map = {
+  ? "14240:1.0": led,
+  ? "14301:1.0": config,
+  * tstr => any
+}
+
+led = {
+  "0": led_inner_object,
+  * tstr => any
+}
+
+led_inner_object = {
+  ? "0": int .size 4,
+  ? "1": int .size 4,
+  ? "2": int .size 4,
+  "99": int .size 8,
+  * tstr => any
+}
+
+config = {
+  "0": config_inner_object,
+  * tstr => any
+}
+
+config_inner_object = {
+  ? "0": int .size 8,
+  ? "1": bool,
+  "99": int .size 8,
+  * tstr => any
+}

app/src/main.c

@@ -16,6 +16,7 @@
 #include "cloud_module.h"
 #include "fota.h"
 #include "location.h"
+#include "cbor_helper.h"
 
 #if defined(CONFIG_APP_LED)
 #include "led.h"
@@ -35,15 +36,14 @@
 /* Register log module */
 LOG_MODULE_REGISTER(main, CONFIG_APP_LOG_LEVEL);
 
-#define MAX_MSG_SIZE	(MAX(sizeof(struct cloud_shadow_response),				\
-			 MAX(sizeof(struct cloud_payload),					\
+#define MAX_MSG_SIZE	(MAX(sizeof(struct cloud_msg),						\
 			 /* Button channel payload size */					\
 			 MAX(sizeof(uint8_t),							\
 			 /* Timer channel payload size */					\
 			 MAX(sizeof(int),							\
 			 MAX(sizeof(enum fota_msg_type),					\
 			 MAX(sizeof(enum location_msg_type),					\
-			 MAX(sizeof(struct network_msg), POWER_MSG_SIZE))))))))
+			 MAX(sizeof(struct network_msg), POWER_MSG_SIZE)))))))
 
 /* Register subscriber */
 ZBUS_MSG_SUBSCRIBER_DEFINE(main_subscriber);
@@ -232,6 +232,7 @@ static const struct smf_state states[] = {
 };
 
 /* Static helper function */
+
 static void task_wdt_callback(int channel_id, void *user_data)
 {
 	LOG_ERR("Watchdog expired, Channel: %d, Thread: %s",
@@ -441,6 +442,7 @@ static void triggering_entry(void *o)
 
 static void triggering_run(void *o)
 {
+	int err;
 	struct main_state *state_object = o;
 
 	if (state_object->chan == &CLOUD_CHAN) {
@@ -454,13 +456,19 @@ static void triggering_run(void *o)
 		}
 
 		if (msg.type == CLOUD_SHADOW_RESPONSE) {
-			/* Missing: Parse the interval received in the shadow response,
-			 * write to state object and schedule new interval
-			 */
+			err = get_update_interval_from_cbor_response(msg.response.buffer,
+								     msg.response.buffer_data_len,
+								     &state_object->interval_sec);
+			if (err) {
+				LOG_ERR("json_parse, error: %d", err);
+				SEND_FATAL_ERROR();
+				return;
+			}
 
-			int err = k_work_reschedule(&trigger_work,
-						    K_SECONDS(state_object->interval_sec));
+			LOG_WRN("Received new interval: %lld seconds", state_object->interval_sec);
 
+			err = k_work_reschedule(&trigger_work,
+						K_SECONDS(state_object->interval_sec));
 			if (err < 0) {
 				LOG_ERR("k_work_reschedule, error: %d", err);
 				SEND_FATAL_ERROR();

app/src/modules/cloud/cloud_module.c

@@ -11,12 +11,10 @@
 #include <zephyr/task_wdt/task_wdt.h>
 #include <net/nrf_cloud.h>
 #include <net/nrf_cloud_coap.h>
+#include <nrf_cloud_coap_transport.h>
+#include <zephyr/net/coap.h>
 #include <app_version.h>
 
-#if defined(CONFIG_MEMFAULT)
-#include <memfault/core/trace_event.h>
-#endif /* CONFIG_MEMFAULT */
-
 #include "cloud_module.h"
 #include "app_common.h"
 #include "network.h"
@@ -47,7 +45,7 @@ LOG_MODULE_REGISTER(cloud, CONFIG_APP_CLOUD_LOG_LEVEL);
 #define ENV_MSG_SIZE	0
 #endif /* CONFIG_APP_ENVIRONMENTAL) */
 
-#define MAX_MSG_SIZE	(MAX(sizeof(struct cloud_payload),					\
+#define MAX_MSG_SIZE	(MAX(sizeof(struct cloud_msg),						\
 			 MAX(sizeof(struct network_msg),					\
 			 MAX(BAT_MSG_SIZE, ENV_MSG_SIZE))))
 
@@ -59,7 +57,6 @@ BUILD_ASSERT(CONFIG_APP_CLOUD_WATCHDOG_TIMEOUT_SECONDS >
 ZBUS_MSG_SUBSCRIBER_DEFINE(cloud);
 
 /* Observe channels */
-ZBUS_CHAN_ADD_OBS(PAYLOAD_CHAN, cloud, 0);
 ZBUS_CHAN_ADD_OBS(NETWORK_CHAN, cloud, 0);
 ZBUS_CHAN_ADD_OBS(CLOUD_CHAN, cloud, 0);
 
@@ -73,14 +70,6 @@ ZBUS_CHAN_ADD_OBS(POWER_CHAN, cloud, 0);
 
 /* Define channels provided by this module */
 
-ZBUS_CHAN_DEFINE(PAYLOAD_CHAN,
-		 struct cloud_payload,
-		 NULL,
-		 NULL,
-		 ZBUS_OBSERVERS_EMPTY,
-		 ZBUS_MSG_INIT(0)
-);
-
 ZBUS_CHAN_DEFINE(CLOUD_CHAN,
 		 struct cloud_msg,
 		 NULL,
@@ -467,13 +456,19 @@ static void state_connected_exit(void *o)
 static void shadow_get(bool delta_only)
 {
 	int err;
-	uint8_t recv_buf[CONFIG_APP_MODULE_RECV_BUFFER_SIZE] = { 0 };
-	size_t recv_buf_len = sizeof(recv_buf);
+	struct cloud_msg msg = {
+		.type = CLOUD_SHADOW_RESPONSE,
+		.response = {
+			.buffer_data_len = sizeof(msg.response.buffer),
+		},
+	};
 
 	LOG_DBG("Requesting device shadow from the device");
 
-	err = nrf_cloud_coap_shadow_get(recv_buf, &recv_buf_len, delta_only,
-					COAP_CONTENT_FORMAT_APP_JSON);
+	err = nrf_cloud_coap_shadow_get(msg.response.buffer,
+					&msg.response.buffer_data_len,
+					delta_only,
+					COAP_CONTENT_FORMAT_APP_CBOR);
 	if (err == -EACCES) {
 		LOG_WRN("Not connected, error: %d", err);
 		return;
@@ -486,12 +481,46 @@ static void shadow_get(bool delta_only)
 	} else if (err > 0) {
 		LOG_WRN("Cloud error: %d", err);
 		return;
+	} else if (err == -E2BIG) {
+		LOG_WRN("The provided buffer is not large enough, error: %d", err);
+		return;
 	} else if (err) {
 		LOG_ERR("Failed to request shadow delta: %d", err);
 		return;
 	}
 
-	/* No further processing of shadow is implemented */
+	if (msg.response.buffer_data_len == 0) {
+		LOG_DBG("No shadow delta changes available");
+		return;
+	}
+
+	/* Workaroud: Sometimes nrf_cloud_coap_shadow_get() returns 0 even though obtaining
+	 * the shadow failed. Ignore the payload if the first 10 bytes are zero.
+	 */
+	if (!memcmp(msg.response.buffer, "\0\0\0\0\0\0\0\0\0\0", 10)) {
+		LOG_WRN("Returned buffeør is empty, ignore");
+		return;
+	}
+
+	err = zbus_chan_pub(&CLOUD_CHAN, &msg, K_SECONDS(1));
+	if (err) {
+		LOG_ERR("zbus_chan_pub, error: %d", err);
+		SEND_FATAL_ERROR();
+		return;
+	}
+
+	/* Clear the shadow delta by reporting the same data back to the shadow reported state  */
+	err = nrf_cloud_coap_patch("state/reported", NULL,
+				   msg.response.buffer,
+				   msg.response.buffer_data_len,
+				   COAP_CONTENT_FORMAT_APP_CBOR,
+				   true,
+				   NULL,
+				   NULL);
+	if (err) {
+		LOG_ERR("Failed to patch the device shadow, error: %d", err);
+		return;
+	}
 }
 
 static void state_connected_ready_entry(void *o)
@@ -640,17 +669,20 @@ static void state_connected_ready_run(void *o)
 	}
 #endif /* CONFIG_APP_ENVIRONMENTAL */
 
-	if (state_object->chan == &PAYLOAD_CHAN) {
-		const struct cloud_payload *payload = MSG_TO_PAYLOAD(state_object->msg_buf);
+	if (state_object->chan == &CLOUD_CHAN) {
+		const struct cloud_msg msg = MSG_TO_CLOUD_MSG(state_object->msg_buf);
 
-		err = nrf_cloud_coap_json_message_send(payload->buffer, false, confirmable);
-		if (err == -ENETUNREACH) {
-			LOG_WRN("Network is unreachable, error: %d", err);
-			return;
-		} else if (err) {
-			LOG_ERR("nrf_cloud_coap_sensor_send, error: %d", err);
-			SEND_FATAL_ERROR();
-			return;
+		if (msg.type == CLOUD_PAYLOAD_JSON) {
+			err = nrf_cloud_coap_json_message_send(msg.payload.buffer,
+							       false, confirmable);
+			if (err == -ENETUNREACH) {
+				LOG_WRN("Network is unreachable, error: %d", err);
+				return;
+			} else if (err) {
+				LOG_ERR("nrf_cloud_coap_sensor_send, error: %d", err);
+				SEND_FATAL_ERROR();
+				return;
+			}
 		}
 	}
 

app/src/modules/cloud/cloud_module.h

@@ -16,18 +16,19 @@ extern "C" {
 
 /* Channels provided by this module */
 ZBUS_CHAN_DECLARE(
-	CLOUD_CHAN,
-	PAYLOAD_CHAN
+	CLOUD_CHAN
 );
 
 struct cloud_payload {
 	uint8_t buffer[CONFIG_APP_CLOUD_PAYLOAD_BUFFER_MAX_SIZE];
-	size_t buffer_len;
+	/* Length of the data stored inside the buffer */
+	size_t buffer_data_len;
 };
 
 struct cloud_shadow_response {
 	uint8_t buffer[CONFIG_APP_CLOUD_SHADOW_RESPONSE_BUFFER_MAX_SIZE];
-	size_t buffer_len;
+	/* Length of the data stored inside the buffer */
+	size_t buffer_data_len;
 };
 
 enum cloud_msg_type {
@@ -43,11 +44,10 @@ enum cloud_msg_type {
 struct cloud_msg {
 	enum cloud_msg_type type;
 	struct cloud_payload payload;
+	struct cloud_shadow_response response;
 };
 
 #define MSG_TO_CLOUD_MSG(_msg)	(*(const struct cloud_msg *)_msg)
-#define MSG_TO_PAYLOAD(_msg)	((struct cloud_payload *)_msg)
-#define MSG_TO_SHADOW_RESPONSE(_msg)	(*(const struct cloud_shadow_response *)_msg)
 
 #ifdef __cplusplus
 }