TPCANMsgFD

typedef struct
{
    DWORD ID;
    TPCANMessageType MSGTYPE;
    BYTE DLC;
    BYTE DATA[64];
} TPCANMsgFD;

TPCANMsgFD = record
    ID: Longword;
    MSGTYPE: TPCANMessageType;
    DLC: Byte;
    DATA: array[0..63] of Byte;
end;

public struct TPCANMsgFD
{
    public uint ID;
    [MarshalAs(UnmanagedType.U1)]
    public TPCANMessageType MSGTYPE;
    public byte DLC;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 64)]
    public byte[] DATA;
}

public value struct TPCANMsgFD
{
    UInt32 ID;
    [MarshalAs(UnmanagedType::U1)]
    TPCANMessageType MSGTYPE;
    Byte DLC;
    [MarshalAs(UnmanagedType::ByValArray, SizeConst = 64)]
    array<Byte>^ DATA;
};

Public Structure TPCANMsgFD
    Public ID As UInt32
    <MarshalAs(UnmanagedType.U1)> _
    Public MSGTYPE As TPCANMessageType
    Public DLC As Byte
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=64)> _
    Public DATA As Byte()
End Structure

from ctypes import *
class TPCANMsgFD (Structure):
    _fields_ = [ ("ID",      c_uint),
                 ("MSGTYPE", TPCANMessageType),
                 ("DLC",     c_ubyte),
                 ("DATA",    c_ubyte * 64) ]

The members of this structure are sequentially byte aligned.

Longer Data field with CAN FD messages: 

The length of data bytes contained in a CAN message is given by the DATA LENGTH CODE field (DLC). The coding of the DLC within FD messages is different. There are 7 additional codes (from 9 to 15) that allows a FD Messages to transport up to 64 bytes of data. The relationship between DLC and data bytes length is as follow:

CAN_ReadFD (class-method: ReadFD) 

CAN_WriteFD (class-method: WriteFD)