Sending messages to Azure IoT Hub and IoT Central

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Examples

Code example, sending messages

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Config app_manifest.json sample

• Connecting to IoT Central

1. Set ID Scope
2. Set Allowed connections
3. Set DeviceAuthentication

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Functions

bool dx_isAzureConnected(void);
bool dx_azurePublish(const void* message, size_t messageLength, DX_MESSAGE_PROPERTY** messageProperties, size_t messagePropertyCount, DX_MESSAGE_CONTENT_PROPERTIES* messageContentProperties);
DX_MESSAGE_CONTENT_PROPERTIES* messageContentProperties);
void dx_azureConnect(DX_USER_CONFIG* userConfig, const char* networkInterface, const char* plugAndPlayModelId);
void dx_azureToDeviceStop(void);

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Structures

typedef struct DX_MESSAGE_PROPERTY
{
	const char* key;
	const char* value;
} DX_MESSAGE_PROPERTY;

typedef struct DX_MESSAGE_CONTENT_PROPERTIES
{
	const char* contentEncoding;
	const char* contentType;
} DX_MESSAGE_CONTENT_PROPERTIES;

dx_config.h

typedef enum {
    DX_CONNECTION_TYPE_NOT_DEFINED = 0,
    DX_CONNECTION_TYPE_DPS = 1,
    DX_CONNECTION_TYPE_DIRECT = 2
} ConnectionType;

typedef struct {
    const char* idScope; 
    const char* connectionString;
    ConnectionType connectionType;
} DX_USER_CONFIG;

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Usage

Declare message template, and optionally message and content properties

static const char* msgTemplate = "{ \"Temperature\":%3.2f, \"Humidity\":%3.1f, \"Pressure\":%3.1f }";

static DX_MESSAGE_PROPERTY* telemetryMessageProperties[] = {
	&(DX_MESSAGE_PROPERTY) { .key = "appid", .value = "hvac" },
	&(DX_MESSAGE_PROPERTY) {.key = "type", .value = "telemetry" },
	&(DX_MESSAGE_PROPERTY) {.key = "schema", .value = "1" }
};

static DX_MESSAGE_CONTENT_PROPERTIES telemetryContentProperties = {
	.contentEncoding = "utf-8",
	.contentType = "application/json"
};

Open connetion to Azure IoT Hub or IoT Central

dx_azureConnect(&dx_config, NETWORK_INTERFACE, IOT_PLUG_AND_PLAY_MODEL_ID);

Send message with no properties

bool serialization_result = dx_jsonSerialize(msgBuffer, sizeof(msgBuffer), 4, 
	DX_JSON_INT, "MsgId", msgId++,
	DX_JSON_DOUBLE, "Temperature", temperature, 
	DX_JSON_DOUBLE, "Humidity", humidity,
	DX_JSON_DOUBLE, "Pressure", pressure);

if (serialization_result) {

	Log_Debug("%s\n", msgBuffer);

	dx_azurePublish(msgBuffer, strlen(msgBuffer), NULL, 0, NULL);

} else {
	Log_Debug("JSON Serialization failed: Buffer too small\n");
}

Send message with properties

bool serialization_result = dx_jsonSerialize(msgBuffer, sizeof(msgBuffer), 4, 
		DX_JSON_INT, "MsgId", msgId++,
		DX_JSON_DOUBLE, "Temperature", temperature, 
		DX_JSON_DOUBLE, "Humidity", humidity,
		DX_JSON_DOUBLE, "Pressure", pressure);

if (serialization_result) {

	Log_Debug("%s\n", msgBuffer);

	dx_azurePublish(msgBuffer, strlen(msgBuffer), messageProperties, NELEMS(messageProperties), &contentProperties);

} else {
	Log_Debug("JSON Serialization failed: Buffer too small\n");
}

Working Example

Send Message Example