Instructions
UM-0085-B09 DT80 Range User Manual Page 223
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Normally, SMS messages are sent at the start of a session, before a data (Internet) connection is established. Sending
an SMS during
an established session may cause the data connection to be disrupted, causing the session to end
prematurely. For this reason, low priority SMS messages will not be sent during an active session – they will be queued
and sent at the start of the next session (unless they have been in the queue for 24 hours, in which case they will be sent
mid-session, like a normal priority SMS).
Session Time Window
A regular session time window may also be defined by specifying a start and end time. During this time window, the
DT80 will attempt to keep the communications session open continuously. The session timeout criteria listed above
(maximum session duration, minimum session duration and minimum idle time) do not apply
during the time window.
Setting up a time window will therefore allow you to contact the logger for a defined time each day (or hour, or week). It
also allows you to group all of the day's communications into a single time period – perhaps a time period where
communications are cheaper, or a time where the FTP server to which data is being transferred is least busy. Grouping
communications into a single session will also reduce the overall power usage.
In a non power-sensitive application, a "perpetual" time window can also be configured. This will keep the modem
powered at all times and will attempt to maintain a continuous connection to the network.
Session Timing Settings
The following profile settings define the session timing that applies when not within the defined session time window (If
any). These are all in the
MODEM_SESSION section:
• MIN_DURATION_S specifies the minimum session duration (in seconds). Default is 0 (no minimum). For
example, if this is set to 600 (seconds) and an alarm causes a communications session to be established and
an SMS or email sent, then the DT80 will hold the connection open for 10 minutes to allow you to connect to it
using dEX to check the status.
•
MIN_IDLE_S specifies the minimum time (in seconds) that the modem session must be idle (i.e. no data sent
or received) before the session ends. Default is 120 seconds (2 minutes), minimum is 10 seconds. Note that
dEX sends a "heartbeat" message to the logger once a minute while it is running, so if you are running dEX
over a modem connection then the session will normally stay active until you close dEX.
• MAX_DURATION_S specifies a hard session time limit (in seconds). The session will be terminated after this
time, and any communications in progress at the time will be aborted, regardless of the
MIN_DURATION_S
and
MIN_IDLE_S settings. It can be useful if your application has a strict power budget that provides for no
more than x minutes of modem on-time per day. Set this to 0 to disable the session time limit, which is the
default setting.
To define a session time window (which will override the above settings), use the following
MODEM_SESSION settings:
•
TIMING_CONTROL is used to specify whether you want no session time window (OFF), a perpetual time
window where the modem is continuously connected (
ALWAYS) or a configurable time window (CRON). The
default is
OFF.
•
START_CRON is used to configure when the time window should start. It is only applicable if
TIMING_CONTROL is set to CRON. To specify the start time, the "cron" syntax is used – the same as for time
of day schedule triggers (see Trigger at Date/Time (P50)). The default is
0:0:12:*:*:*, which translates to
12:00 daily.
• STOP_CRON is used to configure when the time window should end. The default is 0:0:13:*:*:*, or 13:00
daily. Thus with the default settings (and with
TIMING_CONTROL set to CRON), a one hour communications
time window will be set, from noon to 1pm daily.
Example
The following settings:
PROFILE MODEM_SESSION MAX_DURATION_S=0
PROFILE MODEM_SESSION MIN_DURATION_S=0
PROFILE MODEM_SESSION MIN_IDLE_S=180
PROFILE MODEM_SESSION TIMING_CONTROL=CRON
PROFILE MODEM_SESSION START_CRON=0:0:9:*:*:1-5
PROFILE MODEM_SESSION STOP_CRON=0:30:9:*:*:1-5
specify that
• A half hour time window is defined, from 9:00 until 9:30 on weekdays (1-5 indicates Monday to Friday). The
modem will be powered up and connected to the network during this time period
• If a session needs to be established outside this time window (e.g. due to an alarm or a scheduled data unload)
then it will remain active for as long as it takes to perform the data transfer(s). Once the connection has been
idle for 3 minutes (180 seconds) the session will end and the modem will be turned off.