/// <summary>
/// Generates frames for a broadcast transfer.
/// </summary>
/// <remarks>
/// If the node is in passive mode, only single frame transfers will be allowed (they will be transmitted as anonymous).
///
/// For anonymous transfers, maximum data type ID is limited to 3 (see specification for details).
///
/// Pointer to the Transfer ID should point to a persistent variable and should be updated after every transmission.
/// The Transfer ID value cannot be shared between transfers that have different descriptors.
/// </remarks>
public static IEnumerable <CanFrame> Broadcast(
ulong dataTypeSignature,
int dataTypeId,
byte transferId,
byte nodeId,
UavcanPriority priority,
byte[] payload,
int payloadOffset,
int payloadLen)
{
if (payload == null && payloadLen > 0)
{
throw new ArgumentException(nameof(payload));
}
if (priority > UavcanPriority.Lowest)
{
throw new ArgumentException(nameof(priority));
}
uint canId;
ushort crc = Crc16.InitialValue;
if (nodeId == 0)
{
if (payloadLen > 7)
{
throw new ArgumentException("Node ID expected.", nameof(nodeId));
}
const ushort DTIDMask = (ushort)(1U << UavcanConstants.AnonymousMessageDataTypeIdBitLen) - 1;
if ((dataTypeId & DTIDMask) != dataTypeId)
{
throw new ArgumentException(nameof(dataTypeId));
}
// Anonymous transfer, random discriminator.
ushort discriminator = (ushort)((Crc16.Add(Crc16.InitialValue, payload, payloadOffset, payloadLen)) & 0x7FFEU);
canId = ((uint)priority << 24) | ((uint)discriminator << 9) |
((uint)(dataTypeId & DTIDMask) << 8) | nodeId;
}
else
{
canId = ((uint)priority << 24) | ((uint)dataTypeId << 8) | nodeId;
if (payloadLen > 7)
{
crc = Crc16.AddSignature(crc, dataTypeSignature);
crc = Crc16.Add(crc, payload, payloadOffset, payloadLen);
}
}
return(CreateTxFrames(canId, transferId, crc, payload, payloadOffset, payloadLen));
}
/// <summary>
/// Generates frames for a request or a response transfer.
/// </summary>
/// <remarks>
/// Fails if the node is in passive mode.
///
/// Pointer to the Transfer ID should point to a persistent variable and should be updated after every transmission.
/// The Transfer ID value cannot be shared between transfers that have different descriptors.
/// </remarks>
public static IEnumerable <CanFrame> RequestOrRespond(
int destinationNodeId,
ulong dataTypeSignature,
int dataTypeId,
byte transferId,
byte nodeId,
UavcanPriority priority,
UavcanRequestResponse kind,
byte[] payload,
int payloadOffset,
int payloadLen)
{
if ((destinationNodeId < UavcanConstants.MinNodeId) || (destinationNodeId > UavcanConstants.MaxNodeId))
{
throw new ArgumentOutOfRangeException(nameof(destinationNodeId));
}
if (payload == null && payloadLen > 0)
{
throw new ArgumentException(nameof(payload));
}
if (priority > UavcanPriority.Lowest)
{
throw new ArgumentException(nameof(priority));
}
if (nodeId == UavcanConstants.BroadcastNodeId)
{
throw new ArgumentException("Anonymous node can send broadcast messages only.", nameof(nodeId));
}
uint canId = ((uint)priority << 24) | ((uint)dataTypeId << 16) |
((uint)kind << 15) | ((uint)destinationNodeId << 8) |
(1U << 7) | nodeId;
ushort crc = Crc16.InitialValue;
if (payloadLen > 7)
{
crc = Crc16.AddSignature(crc, dataTypeSignature);
crc = Crc16.Add(crc, payload, payloadOffset, payloadLen);
}
return(CreateTxFrames(canId, transferId, crc, payload, payloadOffset, payloadLen));
}
public void Crc16Test1()
{
var dtCrc = Crc16.AddSignature(Crc16.InitialValue, 0xEE468A8121C46A9E);
Assert.Equal(0xD9A7, dtCrc);
}