config: Report config to shadow and unify CDDL schema

Unify desired/reported objects into single shadow-object in CDDL
schema. Add automatic reporting of current config (update_interval,
sample_interval) to cloud shadow upon connection. Simplify build
system to generate both encode and decode functions from unified
schema definition.

Update documentation and tests accordingly.

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

Author: simensrostad

app/src/Kconfig.main

@@ -5,22 +5,27 @@
 #
 menu "App"
 
-config APP_SENSOR_SAMPLING_INTERVAL_SECONDS
-	int "Sensor sampling interval"
-	default 600
+config APP_BUFFER_MODE_SAMPLING_INTERVAL_SECONDS
+	int "Sampling interval in buffer mode"
+	default 150
 	help
-	  Interval for triggering sensor data sampling and location search.
-	  In passthrough mode, this timer also triggers cloud shadow and FOTA status polling and data sending.
-	  This is the primary sampling interval for the application.
+	  Interval that determines how often sensor and location data is
+	  collected in buffer mode.
 
 config APP_CLOUD_SYNC_INTERVAL_SECONDS
 	int "Cloud synchronization interval"
-	default 3600
+	default 600
 	help
-	  Interval for cloud synchronization activities including polling and data sending.
-	  This timer triggers cloud shadow and FOTA status polling, and data sending from storage.
-	  The data sending only applies if the storage module is in buffer mode.
-	  This interval is typically longer than the sensor sampling interval.
+	  Interval in seconds that controls how frequently the application
+	  performs cloud-related tasks such as:
+		* Polling the device shadow
+		* Checking for FOTA updates
+		* Transmitting buffered data to the cloud
+	  In buffer mode, this option is typically set to a longer interval
+	  than CONFIG_APP_BUFFER_MODE_SAMPLING_INTERVAL_SECONDS to reduce
+	  power consumption while allowing data aggregation.
+	  In passthrough mode, this option controls both data sampling and
+	  cloud synchronization frequency.
 
 config APP_REQUEST_NETWORK_QUALITY
 	bool "Request network quality"

app/src/cbor/CMakeLists.txt

@@ -7,13 +7,14 @@
 target_sources(app PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/cbor_helper.c)
 target_include_directories(app PRIVATE .)
 
-# generate encoder code using zcbor
+# generate encoder and decoder code using zcbor
 set(zcbor_command
         zcbor code # Invoke code generation
 	--cddl ${CMAKE_CURRENT_SOURCE_DIR}/device_shadow.cddl
 	--decode # Generate decoding functions
+	--encode # Generate encoding functions
 	--short-names # Attempt to make generated symbol names shorter (at the risk of collision)
-	-t desired-object # Create a public API for decoding the "desired-object" type from the cddl file
+	-t shadow-object # Create a public API for encoding and decoding the "shadow-object" type from the cddl file
 	--output-cmake device_shadow.cmake # The generated cmake file will be placed here
 )
 execute_process(COMMAND ${zcbor_command}

app/src/cbor/cbor_helper.c

@@ -5,46 +5,96 @@
  */
 #include <errno.h>
 #include <string.h>
+#include <zcbor_encode.h>
 
 #include "cbor_helper.h"
-#include "device_shadow_decode.h"
+#include "device_shadow_types.h"
 
 #include <zephyr/logging/log.h>
 
 LOG_MODULE_REGISTER(cbor_helper, CONFIG_APP_LOG_LEVEL);
 
 int get_parameters_from_cbor_response(const uint8_t *cbor,
 				      size_t len,
-				      uint32_t *interval_sec,
+				      uint32_t *update_interval,
+				      uint32_t *sample_interval,
 				      uint32_t *command_type)
 {
 	int err;
-	struct desired_object desired_object = { 0 };
+	struct shadow_object shadow = { 0 };
 	size_t decode_len = len;
 
-	if (!cbor || !interval_sec || !command_type || len == 0) {
+	if (!cbor || !update_interval || !sample_interval || !command_type || len == 0) {
 		return -EINVAL;
 	}
 
-	err = cbor_decode_desired_object(cbor, decode_len, &desired_object, &decode_len);
+	err = cbor_decode_shadow_object(cbor, decode_len, &shadow, &decode_len);
 	if (err) {
-		LOG_ERR("cbor_decode_desired_object, error: %d", err);
+		LOG_ERR("cbor_decode_shadow_object, error: %d", err);
 		LOG_HEXDUMP_ERR(cbor, len, "Unexpected CBOR data");
 		return -EFAULT;
 	}
 
-	if (desired_object.config_present && desired_object.config.update_interval_present) {
-		*interval_sec = desired_object.config.update_interval.update_interval;
+	if (shadow.config_present && shadow.config.update_interval_present) {
+		*update_interval = shadow.config.update_interval.update_interval;
 	} else {
 		LOG_DBG("Update interval parameter not present");
 	}
 
-	if (desired_object.command_present) {
-		*command_type = desired_object.command.type;
+	if (shadow.config_present && shadow.config.sample_interval_present) {
+		*sample_interval = shadow.config.sample_interval.sample_interval;
+	} else {
+		LOG_DBG("Sample interval parameter not present");
+	}
+
+	if (shadow.command_present) {
+		*command_type = shadow.command.type;
 		/* ID entry not used */
 	} else {
 		LOG_DBG("Command parameter not present");
 	}
 
 	return 0;
 }
+
+int encode_config_reported_to_cbor(uint32_t update_interval,
+				   uint32_t sample_interval,
+				   uint8_t *buffer,
+				   size_t buffer_size,
+				   size_t *encoded_len)
+{
+	int err;
+	struct shadow_object shadow = { 0 };
+	size_t encode_len;
+
+	if (!buffer || !encoded_len || buffer_size == 0) {
+		return -EINVAL;
+	}
+
+	/* Build shadow object with config section */
+	shadow.config_present = true;
+
+	if (update_interval != UINT32_MAX) {
+		shadow.config.update_interval_present = true;
+		shadow.config.update_interval.update_interval = update_interval;
+	}
+
+	if (sample_interval != UINT32_MAX) {
+		shadow.config.sample_interval_present = true;
+		shadow.config.sample_interval.sample_interval = sample_interval;
+	}
+
+	/* Encode the shadow object to CBOR */
+	err = cbor_encode_shadow_object(buffer, buffer_size, &shadow, &encode_len);
+	if (err) {
+		LOG_ERR("cbor_encode_shadow_object, error: %d", err);
+		return (err == ZCBOR_ERR_NO_PAYLOAD) ? -ENOMEM : -EFAULT;
+	}
+
+	*encoded_len = encode_len;
+
+	LOG_DBG("Encoded config: update_interval=%u, sample_interval=%u, len=%zu",
+		update_interval, sample_interval, encode_len);
+
+	return 0;
+}

app/src/cbor/cbor_helper.h

@@ -12,10 +12,11 @@
 /**
  * @brief Get the device shadow parameters from a CBOR buffer.
  *
- * @param[in]  cbor         The CBOR buffer.
- * @param[in]  len          The length of the CBOR buffer.
- * @param[out] interval_sec Update interval in seconds.
- * @param[out] command_type Cloud command type.
+ * @param[in]  cbor              The CBOR buffer.
+ * @param[in]  len               The length of the CBOR buffer.
+ * @param[out] update_interval   Update interval in seconds.
+ * @param[out] sample_interval   Sample interval in seconds.
+ * @param[out] command_type      Cloud command type.
  *
  * @returns 0 If the operation was successful.
  *	    Otherwise, a (negative) error code is returned.
@@ -24,5 +25,27 @@
  */
 int get_parameters_from_cbor_response(const uint8_t *cbor,
 				      size_t len,
-				      uint32_t *interval_sec,
+				      uint32_t *update_interval,
+				      uint32_t *sample_interval,
 				      uint32_t *command_type);
+
+/**
+ * @brief Encode device configuration parameters to CBOR for shadow reporting.
+ *
+ * @param[in]  update_interval  Update interval in seconds.
+ * @param[in]  sample_interval  Sample interval in seconds.
+ * @param[out] buffer           Buffer to store encoded CBOR data.
+ * @param[in]  buffer_size      Size of the output buffer.
+ * @param[out] encoded_len      Length of encoded data.
+ *
+ * @returns 0 If the operation was successful.
+ *	    Otherwise, a (negative) error code is returned.
+ * @retval -EINVAL if parameters are invalid.
+ * @retval -ENOMEM if buffer is too small.
+ *
+ */
+int encode_config_reported_to_cbor(uint32_t update_interval,
+				   uint32_t sample_interval,
+				   uint8_t *buffer,
+				   size_t buffer_size,
+				   size_t *encoded_len);

app/src/cbor/device_shadow.cddl

@@ -1,25 +1,44 @@
-; Device Shadow Desired Object Definition
-; ---------------------------------------
-; This section defines the structure of the "desired" object in the device shadow.
-; All sections are optional, but if present, they must appear in the specified order when decoding the CBOR buffer.
+; Device Shadow Object Definition
+; --------------------------------
+; This unified structure defines both "desired" (cloud-to-device) and "reported" (device-to-cloud)
+; objects in the device shadow. All sections are optional, but if present, they must appear in 
+; the specified order when decoding the CBOR buffer.
 ;
 ; Sections:
-; 1. "config": Contains device configuration parameters.
-;    - "update_interval": (optional) A 4-byte unsigned integer specifying the update interval.
+; 1. "config": Device configuration parameters.
+;    - "update_interval": (optional) A 4-byte unsigned integer (in seconds) specifying how often the device
+;                         synchronizes with the cloud (polls shadow, checks for FOTA updates, sends buffered data).
+;                         Valid range: 1 to 4294967294 (excludes 0 and UINT32_MAX).
+;    - "sample_interval": (optional) A 4-byte unsigned integer (in seconds) specifying how often the device
+;                         samples sensor data.
+;                         Valid range: 1 to 4294967294 (excludes 0 and UINT32_MAX).
+;
+; Storage mode behavior:
+;   - Buffer mode:      Activated when both "update_interval" and "sample_interval" are present.
+;                       Device samples at "sample_interval" and sends data at "update_interval".
+;   - Passthrough mode: Activated when only "update_interval" is present ("sample_interval" absent).
+;                       Device samples and sends data at "update_interval".
 ;    - Additional configuration parameters may be included as key-value pairs (tstr => any).
 ;
 ; 2. "command": (optional) An array specifying a command for the device to execute.
 ;    - Structure: [type, id]
 ;      - type: 4-byte unsigned integer indicating the command type.
+;              Supported command types:
+;                1 = PROVISION: Triggers device provisioning sequence
+;                2 = REBOOT:    Triggers device reboot
+;              Valid range: 1 to 2.
 ;      - id:   4-byte unsigned integer indicating the command ID.
+;              Used to track command execution. Increment for successive commands.
+;              Valid range: 1 to 4294967294 (excludes 0 and UINT32_MAX).
 ;
 ; Any additional fields may be included as key-value pairs (tstr => any).
 
-desired-object = {
+shadow-object = {
     ? "config": {
-        ? "update_interval": uint .size 4,
+        ? "update_interval": uint .size 4 .ge 1 .le 4294967294,
+        ? "sample_interval": uint .size 4 .ge 1 .le 4294967294,
         * tstr => any
     },
-    ? "command": [type: uint .size 4, id: uint .size 4],
+    ? "command": [type: uint .size 4 .ge 1 .le 2, id: uint .size 4 .ge 1 .le 4294967294],
     * tstr => any
 }