Integration Manual

SARA-R4/N4 series - System Integration Manual

UBX-16029218 - R13 System description Page 35 of 119

1.13.7 Firmware update Over AT (FOAT)

This feature allows upgrading of the module firmware over the AT interface, using AT commands.

The +UFWUPD AT command enables a code download to the device from the host via the Xmodem protocol.

The +UFWINSTALL AT command then triggers a reboot, and upon reboot initiates a firmware installation on the device

via a special boot loader on the module. The bootloader first authenticates the downloaded image, then installs it, and

then reboots the module.

Firmware authenticity verification is performed via a security signature. The firmware is then installed, overwriting the

current version. In case of power loss during this phase, the boot loader detects a fault at the next wake-up, and restarts

the firmware installation. After completing the upgrade, the module is reset again and wakes-up in normal boot.

For more details about Firmware update Over AT procedure, see the SARA-R4/N4 series AT Commands Manual [2],

+UFWUPD AT command.

1.13.8 Firmware update Over The Air (uFOTA)

This feature allows upgrading the module firmware over the air interface, based on u-blox client/server solution (uFOTA),

using LWM2M.

For more details about firmware update over-the-air procedure, see the SARA-R4/N4 series AT Commands Manual [2].

1.13.9 Power saving

1.13.9.1 Guidelines to optimize power consumption

The LTE Cat M1 / NB1 technology is mainly intended for applications that only require a small amount of data exchange

per day (i.e. a few bytes in uplink and downlink per day). Depending on the application type, the battery may be

required to last for a few years. For these reasons, the whole application board should be optimized in terms of current

consumption and should carefully take into account the following aspects:

• Enable the low power mode configuration using the AT+UPSV command (for the complete description of the

AT+UPSV command, see the SARA-R4/N4 series AT Commands Manual [2]).

• Enable the power saving mode configuration using the AT+CPSMS command (for the complete description of the

AT+CPSMS command, see the SARA-R4/N4 series AT Commands Manual [2]).

• Use the UART interface instead of the USB interface as a serial communication interface, because the current

consumption of the module is ~20 mA higher when the USB interface is enabled.

• Use an application processor with a UART interface working at the same voltage level (1.8 V) as the module. In this

way it is possible to avoid voltage translators, which helps to minimize current leakage.

• If the USB interface is implemented in the design, remove the external USB VBUS voltage from the VUSB_DET input

when serial communication is not necessary, letting the module enter the Power Saving Mode defined in 3GPP Rel.13:

the module does not enter the deep sleep power saving mode if the USB interface is enabled.

• Minimize current leakage on the power supply line.

• Optimize the antenna matching, since a mismatched antenna leads to higher current consumption.

• Monitor V_INT level to sense when the module enters power-off mode or deep sleep power saving mode.

• Disconnect the VCC supply source from the module when it is switched off (see 2.2.1.9).

• Disconnect the VCC supply source from the module during deep sleep power saving mode (see 2.2.1.9): using a host

application processor equipped with a RTC, the module can execute a standard PSM procedure and store the NAS

protocol context in non-volatile memory, and then rely on the host application processor for running its RTC and

triggering wake-up upon need

The use of an external RTC during deep sleep power saving mode is not supported by the “00”, “01” and “x2” product versions