Presently the support in firmware is at the level of CoAP draft 7. This page describes the changes required to support draft 18.

opencoap.h

• COAP_OPTION_NUM_ACCEPT should be 17.
• Add SIZE1 as 60

opencoap.c

coap options in opencoap_receive()

• option delta (type) presently does not handle values 13 and 14. Ditto for option length.