NRF52840 Thread publish max payload length

RE: NRF52840 Thread publish max payload length

haakonsh — Wed, 01 Aug 2018 08:39:15 GMT

Hmm that is dependent on the MQTTSN protocol overhead who in turn is dependent on the Thread stack overhead (UDP packet over 6LoWPAN), and both MQTTSN and 6LoWPAN probably have options and configurations that increase/decrease that overhead. We're a bit short staffed during the summer vacation, but i'll try to find an answer, it's buried in the Thread and MQTTSN spec somewhere.

RE: NRF52840 Thread publish max payload length

Leandro Zimmer — Tue, 31 Jul 2018 20:29:32 GMT

Thank you. I understand. Then I redefine my question.
What's is the max length for the payload data in "mqttsn_packet_sender_publish" method, for sending only one packet of 127bytes, without fragmentation?

RE: NRF52840 Thread publish max payload length

haakonsh — Tue, 31 Jul 2018 13:50:02 GMT

Max packet length of 802.15.4 MAC layer is 127 bytes and the 6LoWPAN layer will dis/assemble its packets to/from 127 byte MAC layer packets. This means that from the application perspective you can operate on packets much larger than 127 bytes.

RE: NRF52840 Thread publish max payload length

Leandro Zimmer — Tue, 31 Jul 2018 13:20:27 GMT

My question is because of the specifications:

IEEE 802.15.4 – 127 bytes (payload)

RE: NRF52840 Thread publish max payload length

haakonsh — Tue, 31 Jul 2018 12:45:43 GMT

I believe the maximum message length is 2^16 bytes as the set and get length functions operate with uint16_t, given that there is enough space in the buffer and message queue ofc.