--- title: Default Topics and Descriptions slug: manufacturing-connect-edge-v1/default-topics-and-descriptions docTags: createdAt: 2022-12-21T14:59:18.000Z --- Review the following information on default topics and descriptions. To review use cases for topics, see [Topic Use Cases (PLC Status, Poll-once, Write, Manage, Batch Write)](docId:0E9j90YlA4NnRKHEle2cE). :::hint{type="info"} **Notes**: - You need to follow the following guidelines for topic names: [Subject-Based Messaging](https://docs.nats.io/nats-concepts/subjects). - When publishing structured data such as JSON, you must convert to a byte array (string) first. To do this in a flow, you can use the **json **node. ::: # Data Publishing Formats DeviceHub collects data from PLCs and sends data to a message broker for further distribution. Data flows trigger using an API call or execute according to a schedule. Manufacturing Connect Edge supports multiple data formats. Refer to the following formats used for data in devices. ## Raw Topics DeviceHub [Tags](docId\:aTR2GYU0e5CI5wb_4moZm) generate a Raw Topic, which is a local topic for publishing and subscribing data through the message broker. Manufacturing Connect Edge publishes each value to a tag-specific topic in the following topic format: **devicehub.raw.\{deviceID}.\{tagID}**. ### Device Raw Topics When you copy a raw topic for a device in Manufacturing Connect Edge, the topic is copied in the following format: `devicehub.raw.{DeviceID}.>`. The ">" character represents a wildcard. This means that the topic will be used for any tag associated with the device. ### Example of a Raw Topic `devicehub.raw.F7F72687-2F29-46E7-95E2-B5532471EBAA.2d7473c0-83a0-4174-83cc-b48a63c1b1cf` ### Example of a Raw Device Topic `devicehub.raw.16AC16F7-5E36-4EA0-8D00-17386C051281.>` ## Alias Topics When you [Connect a Device](docId\:RFVIJdxz7DBAd8mwbismA), you have the option of using the **Enable alias topics** option. If you select to use alias topics for a device, then you won't be able to use raw topics as well. Each connected device can either use alias topics or raw topics, not both. :::hint{type="warning"} **Important**: When alias topics are enabled for a device, you can't use batch write topics. To use batch write topics, you must not select the **Enable alias topics** check box in the device configuration. See [Connect a Device](docId\:RFVIJdxz7DBAd8mwbismA) and [Manage Devices](docId:_uC67Yvju_fop8hAGr3Bb) for more information. ::: When the* Enable alias topics *check box is selected: - deviceId in the raw topic format is replaced with deviceName - tagId in the raw topic format is replaced with tagName Alias topics use the following format: **devicehub.alias.\{devicename}.\{tagname}**. ### Example of an Alias Topic `devicehub.alias.plc2.tag1` ## Write Topics Write topics write data to a tag-specific topic in the following topic format: **devicehub.write.\{deviceID}.\{tagID**}. Each device instance on the **devicehub.write.\{deviceID}.\*** topic receives all messages for the corresponding device. The device instance executes a write to the specified tag on the connected device. ### Example of a Write Topic `devicehub.write.F7F72687-2F29-46E7-95E2-B5532471EBAA.2d7473c0-83a0-4174-83cc-b48a63c1b1cf` ## Batch Write Topics Batch write topics can send multiple write requests simultaneously in the following format: **devicehub.batch\_write.\{deviceID}**. :::hint{type="warning"} **Important**: - Only Gen 2 drivers can use batch write topics. See the [Industrial Systems Connection Guide](docId\:q9SCSsQe-xXk9DG9by8vR) to review available Gen 2 drivers. - This is only available for devices that don't select the** Enable Alias Topics** check box in the device configuration. You must use tags in the raw topic format. See [Connect a Device](docId\:RFVIJdxz7DBAd8mwbismA) and [Manage Devices](docId:_uC67Yvju_fop8hAGr3Bb) for more information. ::: ### Example of a Batch Write Topic `devicehub.batch_write.710B913B-B915-4450-9122-8D57E803499B` ## Poll-Once Topics Poll-once topics can be used to trigger a poll to a tag for data in the following topic formats: - If raw topics are enabled: **devicehub.pollonce.\{deviceID}.\{tagID}** - If alias topics are enabled: **devicehub.pollonce.\{deviceName}.\{tagName}** When a poll-once topic is triggered by a message, Manufacturing Connect Edge will get data for that tag and publish a message to the raw or alias topic for that tag. ### Example of a Poll-Once Topic `devicehub.pollonce.F7F72687-2F29-46E7-95E2-B5532471EBAA.2d7473c0-83a0-4174-83cc-b48a63c1b1cf` ## Topic Formats The following table summarizes the types of device-level and tag-level topics, either with or without aliases. You have the option of using raw topics or alias topics. | **Category** | **Topics** | **Notes** | | ------------ | --------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------- | | Device | devicehub.plcstatus.\{DeviceID} | Subscription to a device status | | Device | devicehub.manage.\{DeviceID} | To START/STOP the device's CONNECTION | | Device | devicehub.raw.\{DeviceID}.> | Publish/Subscribe to all data from a specific Device. The ">" character represents a wildcard. | | Device | devicehub.plcstatus.\{DeviceName} | To monitor the device's CONNECTION/DISCONNECTION status with Alias topics enabled | | Device | devicehub.manage.\{DeviceName} | To START/STOP the device CONNECTION with Alias topics enabled | | Device | devicehub.raw.\{DeviceName}.> | A wildcard to receive messages from all tags added to the device with Alias topics enabled. The ">" character represents a wildcard. | | Device | devicehub.batch\_write.\{DeviceID} | Send multiple write requests simultaneously | | Tag | devicehub.pollonce.\{DeviceID}.\{TagID} | Trigger this topic to get data from a tag one time | | Tag | devicehub.pollonce.\{DeviceName}.\{TagName} | To receive data from a poll-once raw topic with Alias topics enabled | | Tag | devicehub.raw.\{DeviceID}.\{TagID} | To receive data in raw format | | Tag | devicehub.write.\{DeviceID}.\{TagID} | To write data | | Tag | devicehub.alias.\{DeviceName}.\{TagName} | To receive data in raw format with Alias topics enabled
| | Tag | devicehub.write.\{DeviceName}.\{TagName} | To write data with Alias topics enabled
| | Events | system.events | Subscription to all system events |