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I have the UE910 cellular module from Telit. I have manufactured a PCB containing the module but it's not working (power is reaching it but serial program not communicating with the tx and rx pins). I know now that the problem maybe is that I left 2 pins ("On/OFF" and "HW_Shutdown") unconnected even though the datasheet recommends connecting them.

I attached some screenshots from the datasheet.

It is written however that the "HW_shutddown" pin can be left floating as it is internally pulled up so it might be the "ON/OFF" one that need to be connected. Can you help me state the functionality of that pin? Do you think it is the reason why the module is not working?

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No where in the text you copied does it say that HW_SHUTDOWN* is internally pulled up. Instead it states that this pin must not be left floating. Since it is active low for shutdown, I’d tie it to Vcc (1.8V).

As for ON_OFF*, while it is internally pulled up, you must pulse it low for at least 5 seconds to activate the unit, as shown in section 5.2 that you included.

The text you included seems quite clear. I’m not sure what is confusing you.

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