app_sensors: use CBOR instead of JSON

The default Golioth Pipeline for a new project applies to CBOR data and not
JSON data. This updates the data type to use CBOR.

NOTE: By default the pipeline will not include the path with the data. The
RD Template sends to the "sensor" path, but LightDB data will not be shown
under that path unless an inject transform is added.

Signed-off-by: Mike Szczys <[email protected]>

Author: szczys

src/app_sensors.c

@@ -9,6 +9,7 @@ LOG_MODULE_REGISTER(app_sensors, LOG_LEVEL_DBG);
 
 #include <golioth/client.h>
 #include <golioth/stream.h>
+#include <zcbor_encode.h>
 #include <zephyr/drivers/gpio.h>
 #include <zephyr/kernel.h>
 
@@ -24,11 +25,7 @@ LOG_MODULE_REGISTER(app_sensors, LOG_LEVEL_DBG);
 static struct golioth_client *client;
 /* Add Sensor structs here */
 
-/* Formatting string for sending sensor JSON to Golioth */
-#define JSON_FMT "{\"counter\":%d}"
-
 /* Callback for LightDB Stream */
-
 static void async_error_handler(struct golioth_client *client,
 				const struct golioth_response *response,
 				const char *path,
@@ -45,8 +42,8 @@ static void async_error_handler(struct golioth_client *client,
 void app_sensors_read_and_stream(void)
 {
 	int err;
-	char json_buf[256];
 
+	/* Golioth custom hardware for demos */
 	IF_ENABLED(CONFIG_ALUDEL_BATTERY_MONITOR, (
 		read_and_report_battery(client);
 		IF_ENABLED(CONFIG_LIB_OSTENTUS, (
@@ -55,35 +52,56 @@ void app_sensors_read_and_stream(void)
 		));
 	));
 
+	/* Send sensor data to Golioth */
 	/* For this demo, we just send counter data to Golioth */
-	static uint8_t counter;
+	static uint16_t counter;
 
-	/* Send sensor data to Golioth */
-	/* For this demo we just fake it */
-	snprintk(json_buf, sizeof(json_buf), JSON_FMT, counter);
-	LOG_DBG("%s", json_buf);
+	/* Encode sensor data using CBOR serialization */
+	uint8_t cbor_buf[13];
 
+	ZCBOR_STATE_E(zse, 1, cbor_buf, sizeof(cbor_buf), 1);
+
+	bool ok = zcbor_map_start_encode(zse, 1) &&
+		  zcbor_tstr_put_lit(zse, "counter") &&
+		  zcbor_uint32_put(zse, counter) &&
+		  zcbor_map_end_encode(zse, 1);
+
+	if (!ok) {
+		LOG_ERR("Failed to encode CBOR.");
+		return;
+	}
+
+	size_t cbor_size = zse->payload - cbor_buf;
+
+	LOG_DBG("Streaming counter: %d", counter);
+
+	/* Stream data to Golioth */
 	err = golioth_stream_set_async(client,
 				       "sensor",
-				       GOLIOTH_CONTENT_TYPE_JSON,
-				       json_buf,
-				       strlen(json_buf),
+				       GOLIOTH_CONTENT_TYPE_CBOR,
+				       cbor_buf,
+				       cbor_size,
 				       async_error_handler,
 				       NULL);
 	if (err) {
 		LOG_ERR("Failed to send sensor data to Golioth: %d", err);
 	}
 
+	/* Golioth custom hardware for demos */
 	IF_ENABLED(CONFIG_LIB_OSTENTUS, (
 		/* Update slide values on Ostentus
 		 *  -values should be sent as strings
 		 *  -use the enum from app_sensors.h for slide key values
 		 */
-		snprintk(json_buf, sizeof(json_buf), "%d", counter);
-		slide_set(UP_COUNTER, json_buf, strlen(json_buf));
-		snprintk(json_buf, sizeof(json_buf), "%d", 255 - counter);
-		slide_set(DN_COUNTER, json_buf, strlen(json_buf));
+		char sbuf[32];
+
+		snprintk(sbuf, sizeof(sbuf), "%d", counter);
+		slide_set(UP_COUNTER, sbuf, strlen(sbuf));
+		snprintk(sbuf, sizeof(sbuf), "%d", 65535 - counter);
+		slide_set(DN_COUNTER, sbuf, strlen(sbuf));
 	));
+
+	/* Increment for the next run */
 	++counter;
 }