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LINX Packet Structure

A LINX command packet is variable size and consists of a start of frame (SoF), the packet size (bytes), a 16-bit packet number, a 16-bit command byte, a variable number of argument bytes and a checksum. A LINX packet is limited to 60 bytes total and can contain up to 54 bytes of data. LINX packets are sent MSB first.

  • Command Packet
  • Response Packet
    • Command Packet
    Description The structure of a generic LINX command packet (sent from LabVIEW).
    Size Variable
    Format
    0
    1
    2
    3
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    SoF : 0xFF
    PACKET SIZE
    PACKET NUM
    4
    5
    6
    7
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    CMD
    ARG
    CHECKSUM
    SoF Start of Frame. Always 0xFF.
    PACKET SIZE Total packet size in bytes.
    PACKET NUM The Current Packet Number. This value increments with each new packet or repeats for a multi packet command.
    CMD The command byte is used to tell the LINX target which operation to perform
    ARG Arguments for the given command. Variable length.
    CHECKSUM Checksum. Computed by adding all of the bytes in the packet in U8 form ignoring rollover.

    A LINX response packet is sent from the target to LabVIEW. The LINX response packet structure is described below.

    Response Packet
    Description The structure of a generic LINX response packet (sent from LINX target).
    Size Variable
    Format
    -
    0
    1
    2
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    N/A
    SoF : 0xFF
    PACKET SIZE
    PACKET NUM
    3
    4
    5
    6
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    7
    6
    5
    4
    3
    2
    1
    0
    PACKET NUM
    STATUS
    DATA
    CHECKSUM
    SoF Start of Frame. Always 0xFF.
    PACKET SIZE Total packet size in bytes.
    PACKET NUM The packet number of the packet that generated the response.
    STATUS Indicates the target status. This byte is used to return any error generated by the call.
    DATA Return data (if any).
    CHECKSUM Checksum. Computed by adding all of the bytes in the packet in U8 form ignoring rollover.

    Packet Number

    Packet numbering is handled by the host, starting with 0 and increment with each new transaction. Multiple byte transactions will use a single packet number to indicate their grouping. When the target generates a response to a LINX packet the response packet number will match the corresponding command packet number. This could eventually (but will not initially) be used for asynchronous communication. The host will ensure that a response is received for every command packet.

    LINX Spec

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