Installation Instructions

LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information System description
Page 60 of 175
RI signal behavior
The RI module output line is set by default to the OFF state (high level) at UART initialization. Then, during an
incoming call, the RI line is switched from OFF state to ON state with a 4:1 duty cycle and a 5 s period (ON for
1 s, OFF for 4 s, see Figure 26), until the DTE attached to the module sends the ATA string and the module
accepts the incoming data call. The RING string sent by the module (DCE) to the serial port at constant time
intervals is not correlated with the switch of the RI line to the ON state.
Figure 26: RI behavior during an incoming call
The RI line can notify an SMS arrival. When the SMS arrives, the RI line switches from OFF to ON for 1 s (see
Figure 27), if the feature is enabled by the proper AT command (see the u-blox AT Commands Manual [2],
AT+CNMI command).
Figure 27: RI behavior at SMS arrival
This behavior allows the DTE to stay in power saving mode until the DCE related event requests service.
In case of SMS arrival, if several events occur coincidently or in quick succession each event triggers the RI line
independently, although the line will not be deactivated between each event. As a result, the RI line may stay to
ON for more than 1 s.
If an incoming call is answered within less than 1 s (with ATA or if autoanswering is set to ATS0=1) than the RI
line will be set to OFF earlier.
As a result:
RI line monitoring cannot be used by the DTE to determine the number of received SMSes.
In case of multiple events (incoming call plus SMS received), the RI line cannot be used to discriminate the
two events, but the DTE must rely on the subsequent URCs and interrogate the DCE with the proper
commands.
The RI line can additionally notify all the URCs and all the incoming data (PPP, Direct Link, sockets, FTP) on all
LISA-U2 series modules except for “01” product version, if the feature is enabled by the proper AT command
(see the u-blox AT Commands Manual [2], AT+URING command): the RI line is asserted when one of the
configured events occur and it remains asserted for 1 s unless another configured event will happen, with the
same behavior described in Figure 27.
SMS arrives
time [s]
0
RI ON
RI OFF
1s
SMS
time [s]
0
RI ON
RI OFF
1s
1s
time [s]
151050
RI ON
RI OFF
Call incomes
1s
time [s]
151050
RI ON
RI OFF
Call incomes