Communication concepts

Communication concepts related to device operation.

Vicki LoRaWAN device periodically sends messages (keep-alive commands) to the server. The server can then send command to Vicki and the data will be received in the receiving windows, opened after each sent message, according to the LoRaWAN Class A devices protocol. The messages sent period is strict to the LoRaWAN duty cycle requirements. Vicki can send both confirmed/unconfirmed uplink messages depending on its configuration. We recommend configure Vicki for confirmed uplinks, since they provide message retransmission in case of not acknowledge of the sent message.
When a command is sent to Vicki device, this LoRaWAN message type can be with confirmation (recommended). In this way the server is sure the command is received by the device, by checking the ACK bit from the MAC header of the next received packet. If the server doesn’t get a message confirmation, that command must be retransmitted by the server. One sent packet from the server may contain multiple commands for Vicki to optimise communication time. The only restriction is the total number of bytes sent to be less or equal to the allowed application payload size. These sent bytes can combine both multiple write or/and read commands.
If Vicki receives valid command from the server, next uplink sending will be done as soon as possible. In this way the server can check faster the ACK bit, in case of confirmed downlink was received by Vicki, or the requested data or the keep-alive command data.
When the server wants to read some data from the device, the corresponding command code or command codes are sent to the device and the response will be sent together with the next keep-alive message. If the length of the command responses and the keep-alive packet is longer than the allowed by LoRaWAN MAC layer application payload size, the keep-alive packet will be omitted and only the command responses are sent by Vicki.
The aforementioned communication method is also described in Table 1.
Payload byte index
Meaning
0
Command 0 meaning
1
Command 0 data - optional
i
Command 1 meaning - optional
i+1
Command 1 data - optional
j
Command 2 meaning- optional
j+1
Command 2 data - optional
...
...
k
Command x meaning- optional
k+1
Command x data - optional
Table 1
When the server writes some device configuration with a command, the data is stored in the device non-volatile memory, so there isn’t need to send this command again on next network join.
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