SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R08
Objective Specification
System description
Page 79 of 188
SARA-U2 modules, acting as an SAP client, can be connected to an SAP server by a completely wired
connection, as shown in Figure 33.
Device including SARA-U2
GSM/UMTS
Interface
SAP
Serial Interface
(SAP channel over
USB or UART)
Local SIM
(optional)
SARA-U2
SAP Client
Application
Processor
Device including SIM
SAP
Serial Interface
Remote SIM
Mobile
Equipment
SAP Server
Figure 33: Remote SIM access via completely wired connection
As stated in the
SIM Access Profile Interoperability Specification
[28], the SAP client can be connected to the SAP
server by means of a Bluetooth wireless link, using additional Bluetooth transceivers. In this case, the application
processor wired to SARA-U2 modules establishes and controls the Bluetooth connection using the SAP profile,
and routes data received over a serial interface channel to data transferred over a Bluetooth interface and vice
versa, as shown in Figure 34.
Device including SARA-U2
SAP
Serial Interface
(SAP channel over
USB or UART)
GSM/UMTS
Interface
Local SIM
(optional)
SARA-U2
SAP Client
Application
Processor
SAP
Bluetooth
Interface
Bluetooth
Transceiver
Device including SIM
Remote SIM
Mobile
Equipment
SAP Server
Bluetooth
Transceiver
Figure 34: Remote SIM access via Bluetooth and wired connection
The application processor can start an SAP connection negotiation between SARA-U2 module SAP client and an
SAP server using custom AT command (for more details refer to
u-blox AT Commands Manual
While the connection with the SAP server is not fully established, the SARA-U2 module continues to operate
with the attached (local) SIM, if present. Once the connection is established and negotiated, the SARA-U2
module performs a detach operation from the local SIM followed by an attach operation to the remote one.
Then the remotely attached SIM is used for any GSM/UMTS network operation.
URC indications are provided to inform the user about the state of both the local and remote SIM. The insertion
and the removal of the local SIM card are notified if a proper card presence detection circuit using the
SIM_DET
pin of SARA-U2 modules is implemented as shown in the section 2.5, and if the related “SIM card detection”
and “SIM hot insertion/removal” functions are enabled by AT commands (for more details see
u-blox AT
Commands Manual
[3], +UGPIOC, +UDCONF=50 AT commands).
Upon SAP deactivation, the SARA-U2 modules perform a detach operation from the remote SIM followed by an
attach operation to the local one, if present.