The Telit-LTE chips on the LTE lineinterfaces line-interfaces have their own firmware, which can be upgraded. This can be done by connecting the line interface to a Windows PC using a serial to USB cable and running a flash software.
The port should be enabled and configured, but the telephony software should not run.
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The Serial->USB cable is non-standard, because green and white cable are exchanged in comparison to the standard cables which can be ordered.
On this photo the patched cable is connected to port 5 (first port on third line-interface) on an SBC.
For updating port 6 the cable has to be connected to the pins in the next row.
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For Windows to correctly detect the serial connection following drivers must be installed:
https://sixfab.com/wp-content/uploads/2021/06/Telit_Windows_10_WHQL_Drivers_Installer_2.14.0001.zip
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Start the firmware .exe file.
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If everything has been prepared, the firmware install should start, the process usually takes less the
After the firmware update is finished, reboot the gateway.
When the telephony software is running again, check with the gi telnet command the software version which now is installed.