About the allocation of dynamic nodes

pavel.kirienko · July 9, 2021, 11:28am

I think you are missing this bit of the Spec, where the fields of the data type are defined:

UAVCAN/public_regulated_data_types/blob/c043498eacfe90a56e3246d4c2e4ae81aad13082/uavcan/protocol/dynamic_node_id/1.Allocation.uavcan#L134-L146


uint7 node_id
#
# If transfer is anonymous, this field indicates first-stage request.
# If transfer is non-anonymous, this field should be assigned zero and ignored.
#
bool first_part_of_unique_id
#
# If transfer is anonymous, this array must not contain more than MAX_LENGTH_OF_UNIQUE_ID_IN_REQUEST items.
# Note that array is tail-optimized, i.e. it will not be prepended with length field.
#
uint8[<=16] unique_id

You can see from the above that the first byte contains the node-ID in the seven most significant bits (the bit order was changed in v1 btw) and the flag first_part_of_unique_id in the LSB.

The response is the same basically. Note that the last byte of every frame pertains to the transport layer (it’s called the “tail byte”), and the last two bytes of a multi-frame transfer payload contain the transfer-CRC.