BLACKMAGIC Pocket Cinema Camera 6K (CINECAMPOCHDEF6K) - Инструкция по эксплуатации - Страница 145

Abstract Message Packet Format

Every message packet consists of a three byte header followed by an optional variable length data 
block. The maximum packet size is 64 bytes.

Destination device (uint8)

Device addresses are represented as an 8 bit unsigned integer. Individual 
devices are numbered 0 through 254 with the value 255 reserved to indicate a 
broadcast message to all devices.

Command length (uint8) 

The command length is an 8 bit unsigned integer which specifies the length 
of the included command data. The length does NOT include the length of the 
header or any trailing padding bytes.

Command id (uint8)

The command id is an 8 bit unsigned integer which indicates the message type 
being sent. Receiving devices should ignore any commands that they do not 
understand. Commands 0 through 127 are reserved for commands that apply 
to multiple types of devices. Commands 128 through 255 are device specific.

Reserved (uint8)

This byte is reserved for alignment and expansion purposes. It should be set 
to zero.

Command data (uint8[])

The command data may contain between 0 and 60 bytes of data. The format of 
the data section is defined by the command itself. 

Padding (uint8[])

Messages must be padded up to a 32 bit boundary with 0x0 bytes. 
Any padding bytes are NOT included in the command length.

Receiving devices should use the destination device address and or the command identifier to 
determine which messages to process. The receiver should use the command length to skip 
irrelevant or unknown commands and should be careful to skip the implicit padding as well.

Defined Commands

Command 0 : change configuration

Category (uint8)

The category number specifies one of up to 256 configuration categories 
available on the device.

Parameter (uint8)

The parameter number specifies one of 256 potential configuration 
parameters available on the device. Parameters 0 through 127 are device 
specific parameters. Parameters 128 though 255 are reserved for parameters 
that apply to multiple types of devices.

Data type (uint8)

The data type specifies the type of the remaining data. The packet length is 
used to determine the number of elements in the message. Each message 
must contain an integral number of data elements.

Currently defined values are: 

0: void / boolean

A void value is represented as a boolean array of length zero.
The data field is a 8 bit value with 0 meaning false and all other values 
meaning true.

1: signed byte

Data elements are signed bytes

2: signed 16 bit integer

Data elements are signed 16 bit values

3: signed 32 bit integer

Data elements are signed 32 bit values

4: signed 64 bit integer

Data elements are signed 64 bit values

5: UTF-8 string

 Data elements represent a UTF-8 string with no terminating character.

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