Issue-#115 Add support for TC transfer frames

ait/dsn/plugins/TCTF_Manager.py

@@ -0,0 +1,66 @@
+import ait.core
+import ait.dsn.sle.tctf as tctf
+from ait.core.server.plugins import Plugin
+
+
+class TCTF_Manager(Plugin):
+    """
+    Data Processing Pipeline that encodes payloads in TCTF protocol as described by CCSDS standards.
+    https://public.ccsds.org/Pubs/232x0b4.pdf
+
+    The managed parameters are loaded from the AIT config.yaml
+    See CCSDS Blue Book for information regarding managed parameters.
+
+
+    Sample Configuration Part I:
+    ----------------------------
+    server:
+        plugins:
+            - plugin:
+                name: ait.dsn.plugins.TCTF_Manager.TCTF_Manager
+                inputs:
+                    - command_stream
+
+    Sample Configuration Part II:
+    -----------------------------
+    default:
+        dsn:
+            tctf:
+                transfer_frame_version_number: 0
+                bypass_flag: 0
+                control_command_flag: 0
+                reserved: 0
+                uplink_spacecraft_id: 123
+                virtual_channel_id: 0
+                frame_sequence_number: 0
+                apply_error_correction_field: True
+    """
+    def __init__(self, inputs=None, outputs=None, zmq_args=None,
+                 command_subscriber=None, managed_parameters=None):
+        super().__init__(inputs, outputs, zmq_args)
+
+        config_prefix = 'dsn.sle.tctf.'
+        self.tf_version_num = ait.config.get(config_prefix+'transfer_frame_version_number', None)
+        self.bypass = ait.config.get(config_prefix+'bypass_flag', None)
+        self.cc = ait.config.get(config_prefix+'control_command_flag', None)
+        self.rsvd = ait.config.get(config_prefix+'reserved', None)
+        self.scID = ait.config.get(config_prefix+'uplink_spacecraft_id', None)
+        self.vcID = ait.config.get(config_prefix+'virtual_channel_id', None)
+        self.frame_seq_num = ait.config.get(config_prefix+'frame_sequence_number', None)
+        self.apply_ecf = ait.config.get(config_prefix+'apply_error_correction_field', None)
+
+    def process(self, data_field_byte_array, topic=None):
+        frame = tctf.TCTransFrame(tf_version_num=self.tf_version_num,
+                                  bypass=self.bypass, cc=self.cc,
+                                  rsvd=self.rsvd, scID=self.scID,
+                                  vcID=self.vcID,
+                                  frame_seq_num=self.frame_seq_num,
+                                  data_field=data_field_byte_array,
+                                  apply_ecf=self.apply_ecf)
+
+        encoded_frame = frame.encode()
+        ait.core.log.debug(f"TCTF_Manager: {encoded_frame}")
+
+        self.publish(encoded_frame)
+        self.frame_seq_num = (self.frame_seq_num + 1) % 255
+        return encoded_frame

ait/dsn/plugins/__init__.py

@@ -0,0 +1 @@
+

ait/dsn/sle/frames.py

@@ -585,10 +585,3 @@ def decode_dataField_Idle(self, datafield):
 
     def encode(self):
         pass
-
-
-class TCTransFrame(object):
-    ''''''
-    # TODO: Implement
-    # See C Space Data Link Protocol pg. 4-1 for further information
-    pass

ait/dsn/sle/tctf.py

@@ -0,0 +1,245 @@
+from enum import Enum, auto
+from collections import OrderedDict, namedtuple
+from ait.core import log
+from bitstring import BitArray
+import binascii
+
+
+class HeaderKeys(Enum):
+    """HeaderKeys is an Enum used as a key in TCTF hashmaps"""
+    TRANSFER_FRAME_VERSION_NUM = auto()
+    BYPASS_FLAG = auto()
+    CONTROL_COMMAND_FLAG = auto()
+    RESERVED = auto()
+    SPACECRAFT_ID = auto()
+    VIRTUAL_CHANNEL_ID = auto()
+    FRAME_LENGTH = auto()
+    FRAME_SEQ_NUM = auto()
+
+
+class ICD:
+    """
+    Contains definitions and other useful values as defined in the CCSDS ICD, 4.1.2.1
+    https://public.ccsds.org/Pubs/232x0b4.pdf
+    """
+    class Sizes(Enum):
+        """
+        Defines various useful size constants derrived from the CCSDS ICD. 
+        TCTFS in the SDLS Protocol may define values smaller than the ones described here.
+        """
+        MAX_FRAME_OCTETS = 1024
+        MAX_FRAME_BIN = MAX_FRAME_OCTETS * 8
+
+        ECF_OCTETS = 2
+        ECF_BIN = ECF_OCTETS * 8
+
+        PRIMARY_HEADER_OCTETS = 5
+        PRIMARY_HEADER_BIN = PRIMARY_HEADER_OCTETS * 8
+
+        MAX_DATA_FIELD_NO_ECF_OCTETS = 1019
+        MAX_FRAME_NO_ECF_OCTETS = PRIMARY_HEADER_OCTETS + MAX_DATA_FIELD_NO_ECF_OCTETS
+
+        MAX_DATA_FIELD_ECF_OCTETS = MAX_DATA_FIELD_NO_ECF_OCTETS - ECF_OCTETS
+        MAX_FRAME_ECF_OCTETS = PRIMARY_HEADER_OCTETS + MAX_DATA_FIELD_ECF_OCTETS + ECF_OCTETS
+
+        MAX_DATA_FIELD_NO_ECF_BIN = MAX_DATA_FIELD_NO_ECF_OCTETS * 8
+        MAX_DATA_FIELD_ECF_BIN = MAX_DATA_FIELD_ECF_OCTETS * 8
+
+    class Header():
+        """
+        INFO contains a map associating a HeaderKey to a tuple of bit_size and mandatory,
+        which defines the Header Field per CCSDS.
+        """
+        Field = namedtuple('Field', ['bit_size', 'mandatory'])
+        INFO = OrderedDict()
+        INFO[HeaderKeys.TRANSFER_FRAME_VERSION_NUM] = Field(2, True)
+        INFO[HeaderKeys.BYPASS_FLAG] = Field(1, True)
+        INFO[HeaderKeys.CONTROL_COMMAND_FLAG] = Field(1, True)
+        INFO[HeaderKeys.RESERVED] = Field(2, True)
+        INFO[HeaderKeys.SPACECRAFT_ID] = Field(10, True)
+        INFO[HeaderKeys.VIRTUAL_CHANNEL_ID] = Field(6, True)
+        INFO[HeaderKeys.FRAME_LENGTH] = Field(10, True)
+        INFO[HeaderKeys.FRAME_SEQ_NUM] = Field(8, True)
+
+    class CRC:
+        """
+        Contains crc_func.
+        The ICD describes some variation of CRC-16-CCITT, where
+        Name            Poly     Reverse  Remainder    Final XOR  Check
+        crc-ccitt-false 0x11021  False    0xFFFF       0x0000     0x29B1
+        Which is used for generating the ECF section of the TCTF.
+        """
+        crc_func = binascii.crc_hqx
+
+    class HeaderSlices:
+        """
+        HeaderSlices contains SLICES, which maps a HeaderKey to a python slice.
+        The slices are used to extract sections of the frame binary.
+
+        See the TCTransFrame decode function
+        """
+        SLICES = OrderedDict()
+        SLICES[HeaderKeys.TRANSFER_FRAME_VERSION_NUM] = slice(0, 2)
+        SLICES[HeaderKeys.BYPASS_FLAG] = slice(2, 3)
+        SLICES[HeaderKeys.CONTROL_COMMAND_FLAG] = slice(3, 4)
+        SLICES[HeaderKeys.RESERVED] = slice(4, 6)
+        SLICES[HeaderKeys.SPACECRAFT_ID] = slice(6, 16)
+        SLICES[HeaderKeys.VIRTUAL_CHANNEL_ID] = slice(16, 22)
+        SLICES[HeaderKeys.FRAME_LENGTH] = slice(22, 32)
+        SLICES[HeaderKeys.FRAME_SEQ_NUM] = slice(32, 41)
+
+
+class TCTransFrame():
+    """
+    An instance of TCTransFrame fully defines a TCTF. 
+    Encoding is deferred until the encode method is called.
+
+    The static decode method will translate a TCTF binary into a named tuple.
+
+    apply_ecf defines whether the ECF field should be calculated and attached to the TCTF. 
+
+    Parameters are expected to comply with CCSDS standard, and no validation is done on them.
+    """
+    DecodedTCTF = namedtuple('DecodedTCTF', ["header_map", "payload", "ecf"])
+
+    def decode(data, has_ecf=None):
+        if has_ecf:
+            payload = data[5:-2]
+            ecf = data[-2:]
+        else:
+            payload = data[5:]
+            ecf = None
+
+        header = BitArray(data[0:5]).bin
+
+        decoded_header = OrderedDict()
+        for key in HeaderKeys:
+            slice = ICD.HeaderSlices.SLICES[key]
+            val_bin = header[slice]
+            val_eng = int(val_bin, 2)
+            decoded_header[key] = val_eng
+            log.debug(f"TCTransFrame => decode -> {key}, {slice}, Val_Bin:{val_bin}, bin_len={len(val_bin)}, decode={val_eng}")
+
+        return TCTransFrame.DecodedTCTF(decoded_header, payload, ecf)
+
+    def __init__(self, tf_version_num, bypass, cc, rsvd, scID, vcID,
+                 frame_seq_num, data_field, apply_ecf=False):
+
+        """
+        Initialize a TCTF.
+        Encoding the value is deferred until the encode method is called.
+
+        Parameters
+        ----------
+        tf_version_num : TeleCommand Transfer Version Number*
+        bypass : Bypass Flag*
+        cc : Control Command Flag*
+        rsvd : Reserved Space*
+        scID : Spacecraft Identifier*
+        vcID : Virtual Channel Identifier*
+        frame_seq_num : Frame Sequence Number*
+        data_field : Transfer Frame Data Field*, a bytearray representing the TCTF payload.
+        apply_ecf : Flag used to apply ECF frames.
+
+        * See CCSDS ICD for more information regarding parameter meaning and usage.
+        """
+        # Header Data
+        self.primary_header = OrderedDict()
+
+        # Data Field
+        self.encoded_data_field = data_field
+        self.size_data_field_bin = len(self.encoded_data_field) * 8
+
+        # ECF Data
+        self.apply_ecf = apply_ecf
+        self.encoded_crc = None
+        # Finalize ecf size
+        if self.apply_ecf:
+            self.size_ecf_bin = ICD.Sizes.ECF_BIN.value
+        else:
+            self.size_ecf_bin = 0
+
+        # Final Frame Data
+        self.encoded_frame = None
+        self.size_frame_bin = sum([ICD.Sizes.PRIMARY_HEADER_BIN.value,
+                                   self.size_data_field_bin,
+                                   self.size_ecf_bin])
+        # Set Primary Header and defer encoding
+        self.set_primary_header(tf_version_num, bypass, cc, rsvd, scID, vcID,
+                                frame_seq_num)
+
+    def encode(self):
+        """
+        When called, returns bytes representing the TCTF.
+        If called a second time, returns the previously computed TCTF.
+        """
+        # Exit early if we have previously encoded
+        if self.encoded_frame:
+            return self.encoded_frame
+
+        # Finalize primaryheader per ICD
+        self.encode_primary_header()
+
+        #  Attach Payload
+        frame_no_crc_bytes = self.encoded_primary_header + self.encoded_data_field
+
+        # Attach CRC as ECF
+        self.encode_ecf(frame_no_crc_bytes)
+        self.encoded_frame = frame_no_crc_bytes + self.encoded_crc
+
+        return self.encoded_frame
+
+    def set_primary_header(self, tf_version_num, bypass, cc, rsvd, scID, vcID,
+                           frame_seq_num):
+        """
+        Prepares the TCTF instance for generating the TCTF.
+        """
+        # Finalize frame size
+        frame_len = int(self.size_frame_bin / 8)-1
+        log.debug((f"TCTransFrame => set_primary_header -> "
+                   f"FRAMELENGTH: {frame_len}"))
+
+        # Insertion order is critical. Must match ICD order.
+        self.primary_header[HeaderKeys.TRANSFER_FRAME_VERSION_NUM] = tf_version_num
+        self.primary_header[HeaderKeys.BYPASS_FLAG] = bypass
+        self.primary_header[HeaderKeys.CONTROL_COMMAND_FLAG] = cc
+        self.primary_header[HeaderKeys.RESERVED] = rsvd
+        self.primary_header[HeaderKeys.SPACECRAFT_ID] = scID
+        self.primary_header[HeaderKeys.VIRTUAL_CHANNEL_ID] = vcID
+        self.primary_header[HeaderKeys.FRAME_LENGTH] = frame_len
+        self.primary_header[HeaderKeys.FRAME_SEQ_NUM] = frame_seq_num
+
+    def encode_primary_header(self):
+        """
+        Returns bytes representing the primary header.
+        """
+        new_header = BitArray()
+        for header_field, header_data in self.primary_header.items():
+            size = ICD.Header.INFO[header_field].bit_size
+            padded_segment = format(header_data, f'0{size}b')
+            segment = BitArray(bin=padded_segment)
+            new_header.append(segment)
+            log.debug((f"TCTransFrame => encode_primary_header -> "
+                       f"{header_field} ::=> "
+                       f"Encoding: {segment},  "
+                       f"Length: {len(segment)}"))
+        self.encoded_primary_header = new_header.bytes
+        log.debug((f"TCTransFrame => encode_primary_header -> "
+                   f"Header= {new_header}, "
+                   f"Size= {len(new_header)}"))
+        return self.primary_header
+
+    def encode_ecf(self, frame_no_crc_bytes):
+        """
+        Returns bytes representing the ECF segment of the TCTF.
+        If the apply_ecf flag is not set, an empty bytearray is returned.
+        """
+        if self.apply_ecf:
+            crc_val = ICD.CRC.crc_func(frame_no_crc_bytes, 0xFFFF)
+            self.encoded_crc = crc_val.to_bytes(ICD.Sizes.ECF_OCTETS.value,
+                                                byteorder="big")
+        else:
+            self.encoded_crc = bytes()
+        log.debug((f"TCTransFrame => encode_ecg -> Encoded CRC: "
+                   f"{self.encoded_crc}"))
+        return self.encoded_crc