EM7455 Power-Off Sequence

IoT Modules
1

According to the AirPrime EM7455 Specification, there is a recommended power-off sequence to mitigate against on-board file-system corruption. This sequence can take up to 25 seconds.

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QUESTION: If the EM7455 is first made ‘safe to remove’, can the power be cut immediately after?

On Windows, there is a ‘safely remove’ feature, which can be done programmatically using the ’ CM_Request_Device_Eject’ API. Does this permit immediate removal of power?

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2

Hi @timclacy,
Safely remove support to eject device from PC without powering off the module. I tried on Window 10, EM7455 is immediately removed from PC.

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Please share any concerns you have and help us tick Solution if your question is answered
Thanks

3

Hi Vianney,

Yes.

But my question was regarding the power-off sequence in the EM7455 datasheet.

I wanted confirmation that we can ignore the power-off sequence if we first do ‘safely remove’ hardware. In other words, can you confirm that we can cut power immediately after doing ‘safely remove’ without any risk of corruption to the module’s internal file-system.

I suspect it is safe to cut power immediately after ‘safely remove’, which means that the datasheet is a bit misleading.

Cheers

Tim

4

Hi @timclacy,
As I said safely remove is a feature of Window which supports to remove connection between your PC and the module, it doesn’t cut power of the module. It will be turned off only if you unplug the cable from the module. We don’t recommend customer do this because it will cause the unexpected errors afterward.
Thanks

5

Thanks for answering but now you’re saying that you don’t recommend customers unplug the module from USB or it could cause unexpected errors.

In other words, you are saying that after doing ‘safely remove’hardware’ it’s still not safe to remove the hardware. Is that correct?

Thanks

6

@timclacy

The short answer to your question is unfortunately no.

The 25 seconds is an extreme to cover every eventuality, we have put as many safe guards in as possible to guard against corruption but there remain some we just cannot completely mitigate.

Regards

Matt

7

Thanks for the reply.