6 Downlink messages
These messages are sent from the server to the tracker through the LoRa network. They are used to either
configure or manage the tracker. Each message contains a header including:
➢ A message type
➢ An acknowledgement token
The remaining of the message depends on the message type described in the following table.
Notes
1- Any unexpected message (unknown message type, bad length, ...) is discarded. However, the ack
token is updated even if the message is discarded (if the payload is at least 2 bytes long).
2- The LoRa port to be used for downlink is 2.
6.1 Acknowledge token
It provides a way to indicate to the application that a given message has been received by the tracker.
The acknowledge token is transmitted in every uplink message, and it is updated when the tracker receives
a LoRa message. This way, each time the server receives a LoRa uplink, it knows whether the previous
message has been received.
The acknowledge token is four bits size. Its value ranges from 0 to 15 (0x0F).
Notes
1- The ack token value must be changed for each downlink.
2- It’s up to the application to process or not the ack tokens.
3- It’s up to the application to manage the confirmations. It can either wait for the matching ack token
in the uplink message before sending another downlink or send multiple downlink and later waits for
the acks.
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