Max interfaces in the specification

scottdixon · April 11, 2019, 3:20am

I came across this in libuavcan:

/**
 * This limit is defined by the specification.
 */
enum { MaxCanIfaces = 3 };

Which I’ve seen before but I’ve forgotten what in the v0 specification governed this. Does anybody remember? @pavel.kirienko?

pavel.kirienko · April 11, 2019, 1:57pm

The only place where the limit is used in the entire specification (assuming that the standard DSDL defs are part of it) is this:

github.com

UAVCAN/dsdl/blob/3baa2e90a0e8c7b660a2deda8f9a541877ed58e5/uavcan/node/434.GetTransportStatistics.0.1.uavcan#L19


uint8 MAX_PHYSICAL_INTERFACES = 3


# UAVCAN transfer performance statistics:
# the number of UAVCAN transfers sent, received, and failed.
IOStatistics.0.1 transfer_statistics


# Physical interface statistics, separate per interface.
# E.g., for a doubly redundant transport, this array would contain two elements,
# the one at the index zero would apply to the first interface, the other to the second interface.
void6
IOStatistics.0.1[<=MAX_PHYSICAL_INTERFACES] physical_interface_statistics


@assert _offset_ % 8 == {0}
@assert _offset_.max <= (63 * 8)      # One CAN FD frame