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Ack'ed Mode
UDP is not a 100% reliable connection and occasional reports or command/responses may be
lost. Since all commands have responses, the server can repeat any command to which there
is no response. In order to assure reliable reception of reports, Arsenal devices can be
configured either in Normal or Ack'ed mode to send the reports. In the Normal mode the
reports are simply sent "as is" with no acknowledgment from the server. In the Ack'ed mode
every report sent is expected to be acknowledged by the server by sending back an ACK
message back. If acknowledgement is not received within the specified timeout, the report is
re-sent. If the report is not acknowledged after the specified number of attempts, it is queued.
If acknowledgement is received after the report is queued (i.e. past timeout of the last attempt),
it is ignored.
Report is not considered "complete" until its acknowledgement is received. Thus, if report X
is sent and report X+1 is triggered while waiting for acknowledgement of X, report X+1 will
be queued until such acknowledgement is received and only then sent. The Arrow will
attempt to re-send queued report(s) every time a new report is triggered. If there is more than
one report queued, the reports will attempt to be sent in the order of triggering and only once
the report is acknowledged, the next report is attempted. This assures that reports are sent and
received in order.
Ack'ed mode assures that all reports are received, but adds overhead in time and data. Report
that is not acknowledged is sent again and eventually will be queued and sent again. The
number and frequency of re-tries is configurable via the Report Acknowledgement command.
Event Report Format
Reports can be generated in either an ASCII representation of hex or as actual binary encoded
hex. The reporting format is selected via Report Format command. Note that while the logical
content of the report is the same in both representations, the size for an ASCII report is twice
the size of actual numbers of bytes compared to binary representation.
3.6 Reset
There are a number of resets available on the device. Soft reset resets the baseband only by
using an internal watchdog, while hard reset power cycles the whole device. There is also an
option to reset the GPS sub-system only.
Context Preservation
When a reset is caused by the Network Watchdog or by the Reset command (modes 0,1), the
context of the system is being preserved and is restored after the reset. The context includes
all the periodic timers, the report queue, the odometer, etc. This allows to reset the unit as a
troubleshooting measure either periodically or due to Network Watchdog without losing
reports that are already in the queue or are pending on running timers. Note that the reset
process may cause 1-2min of inaccuracy in the timers and should not be considered as very
precise.
© 2018 M-Labs Technologies
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