Module automatically switched off

Hi all,

When I initaite a data call, once data call established the Q2686 module gives +WBCI : 0 response and
module automatically gives CPOF command and switch it off, even though the power supply is connected to the module.
Please suggest a solution that can resolve the above problem.


What do you mean by that?


It means even though power supply is proper, after established a data call it automatically switched off by
giving +WBCI : 0 response and automatically issue CPOF command.

Normally module is on and accepts all commands once I go for data call the above problem occurs.

I am using USB power power supply and not any battery management algorithm or command.

But how does the module itself issue a CPOF command?! :open_mouth:

Or do you just mean that it behaves as if a CPOF command had been issued?

Have you checked carefully that it fully meets the module’s strict power supply requirements at all times?

Look at the voltage very carefully using an oscilloscope directly onto the module’s power pins - I would strongly suspect that you have a power supply problem here…

Don’t search any further, that’s exactly your problem. During network activities the current consumption can rise up to 2A, whereas a an ordinary USB power supply can usually only deliver up to 500 mA (official USB specification). So you either need really big capacitors (at least 1000 uF) or you might think about a small battery used as a buffer.

Best regards,


And, officially, it can only doing that after having specifically negotiated with the Host and established itself as a “high-power” device…

Which will require special attention to ensure that the initial inrush doesn’t “upset” the USB…

Or, as experience learned me, destroy your computer…
(blew a nice tiny hole in my south-bridge once)