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# MessageFormatRequest (UORB message)

**TOPICS:** message_format_request

## Fields

| Name             | Type       | Unit [Frame] | Range/Enum | Description                                                                                                      |
| ---------------- | ---------- | ------------ | ---------- | ---------------------------------------------------------------------------------------------------------------- |
| timestamp        | `uint64`   |              |            | time since system start (microseconds)                                                                           |
| protocol_version | `uint16`   |              |            | Must be set to LATEST_PROTOCOL_VERSION. Do not change this field, it must be the first field after the timestamp |
| topic_name       | `char[50]` |              |            | E.g. /fmu/in/vehicle_command                                                                                     |

## Constants

| Name                                                          | Type     | Value | Description                                                                                                         |
| ------------------------------------------------------------- | -------- | ----- | ------------------------------------------------------------------------------------------------------------------- |
| <a id="#LATEST_PROTOCOL_VERSION"></a> LATEST_PROTOCOL_VERSION | `uint16` | 1     | Current version of this protocol. Increase this whenever the MessageFormatRequest or MessageFormatResponse changes. |

## Source Message

[Source file (GitHub)](https://github.com/PX4/PX4-Autopilot/blob/main/msg/MessageFormatRequest.msg)

::: details Click here to see original file

```c
uint64 timestamp # time since system start (microseconds)

# Request to PX4 to get the hash of a message, to check for message compatibility

uint16 LATEST_PROTOCOL_VERSION = 1 # Current version of this protocol. Increase this whenever the MessageFormatRequest or MessageFormatResponse changes.

uint16 protocol_version           # Must be set to LATEST_PROTOCOL_VERSION. Do not change this field, it must be the first field after the timestamp

char[50] topic_name  # E.g. /fmu/in/vehicle_command
```

:::