Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 System description Page 28 of 119
The ANT_DET pin generates a DC current (for detailed characteristics see the SARA-R4/N4 series Data Sheet [1]) and
measures the resulting DC voltage, thus determining the resistance from the antenna connector provided on the
application board to GND. So, the requirements to achieve antenna detection functionality are the following:
• an RF antenna assembly with a built-in resistor (diagnostic circuit) must be used
• an antenna detection circuit must be implemented on the application board
See section 2.4.2 for antenna detection circuit on application board and diagnostic circuit on antenna assembly design-in
guidelines.
1.8 SIM interface
1.8.1 SIM interface
SARA-R4/N4 series modules provide high-speed SIM/ME interface including automatic detection and configuration of the
voltage required by the connected SIM card or chip.
Both 1.8 V and 3 V SIM types are supported. Activation and deactivation with automatic voltage switch from 1.8 V to 3 V
are implemented, according to ISO-IEC 7816-3 specifications. The VSIM supply output provides internal short circuit
protection to limit start-up current and protect the SIM to short circuits.
The SIM driver supports the PPS (Protocol and Parameter Selection) procedure for baud-rate selection, according to the
values determined by the SIM card or chip.
1.8.2 SIM detection interface
The GPIO5 pin is configured as an external interrupt to detect the SIM card mechanical / physical presence. The pin is
configured as input with an internal active pull-down enabled, and it can sense SIM card presence only if cleanly
connected to the mechanical switch of a SIM card holder as described in section 2.5:
• Low logic level at GPIO5 input pin is recognized as SIM card not present
• High logic level at GPIO5 input pin is recognized as SIM card present
For more details, see the SARA-R4/N4 series AT Commands Manual [2], +UGPIOC, +CIND and +CMER AT commands.