Micro Tracker User Guide FW1.6 V1.1
Page 11 of 17
11 October 2018
Company Confidential
–
restricted distribution
7
Downlink messages
These messages are sent from the server to the tracker through the LoRa network. They are used
to configure the tracker or request a position. Each message contains a header including:
➢
A message type
➢
An acknowledgement token
The remaining of the message depends on the message type. The tracker accepts three types of
downlink messages, listed in the following table:
Message type
ID
Description
POD
0x01
Position on demand
Set Mode
0x02
Change the tracker mode
Set Param
0x0B
Modify a parameter
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.
7.1
Ack Token
It provides a way to indicate to the application that a given message has been received and
processed by the tracker.
The ack 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 ack token is four bits long. Its value ranges from 0 to 15(0x0F).
Notes
1.
The ack token value should be updated for each downlink to be used by the application.
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.
