Complex ACK APDUs return successful results that contain data.

APDU Description (ASHRAE 135)

The BACnet-ComplexACK-PDU is used to convey the information contained in a positive service response primitive that contains information in addition to the fact that the service request was successfully carried out. (Clause 21)

They are the counterpart to BACnet.Protocol.APDU.ConfirmedServiceRequest for services whose positive response carries more than a simple acknowledgment:

• ReadProperty -> list of property values
• ReadPropertyMultiple -> multiple read-access results
• AtomicReadFile / AtomicWriteFile -> file data / confirmation
• GetEventInformation, GetAlarmSummary, ReadRange, etc.

The payload field contains the raw Application Tag encoding of the service-specific response data. Use the corresponding ...Ack modules under BACnet.Protocol.Services.Ack.* (or the service module's from_apdu/1) to interpret the payload in a structured way.

Segmentation

Like Confirmed Service Requests, Complex ACKs may be segmented. The sequence_number and proposed_window_size fields are only meaningful for segmented messages.

This module implements the BACnet.Stack.EncoderProtocol.

Decoding is performed by BACnet.Protocol.APDU.decode/1 (and BACnet.Protocol.APDU.decode_complex_ack/1).

Examples

iex> ack = %ComplexACK{
...>   invoke_id: 12,
...>   service: :read_property,
...>   sequence_number: nil,
...>   proposed_window_size: nil,
...>   payload: [
...>     tagged: {0, <<0, 0x80, 0, 0>>, 4},            # object-identifier (Analog Value, instance 0)
...>     tagged: {1, <<0x55>>, 1},                     # property-identifier (present_value)
...>     constructed: {3, [{:real, 23.5}], 0}          # property-value
...>   ]
...> }
iex> ComplexACK.encode(ack)
{:ok, <<0x30, 0x0C, 0x0C, 0x0C, 0x00, 0x80, 0x00, 0x00, 0x19, 0x55, 0x3E, 0x44, 0x41, 0xBC, 0x00, 0x00, 0x3F>>}

Decoding a ComplexACK:

iex> raw = <<0x30, 0x0C, 0x0C, 0x3E, 0x44, 0x41, 0xA0, 0x00, 0x00, 0x3F>>
iex> BACnet.Protocol.APDU.decode(raw)
{:ok, %ComplexACK{invoke_id: 12, payload: [{:constructed, {3, {:real, 20.0}, 0}}], proposed_window_size: nil, sequence_number: nil, service: :read_property}}