[Ovmsdev] Cannot reset simcom stuck in PoweringOn state without removing module power

Michael Balzer dexter at expeedo.de
Sun Nov 17 20:11:36 HKT 2019

I also saw this & can also reproduce this on my workbench.

Mark, it seems we've got a hardware flaw here: EGPIO output port 0 (MDM_EN) is connected to transistor Q2 base via R16 without any pull-up. As the EGPIO ports
are open drain, that can only work by chance. Maybe R16 was meant to be the pull-up, i.e. be connected to +3.3V, and MDM_EN should be connected directly to the
transistor base?

I've verified this by checking the voltage level at MDM_EN & PWRKEY. When setting the port to 1, MDM_EN only rises for a very short time (too short for my
multimeter to tell), and PWRKEY only drops very briefly. The modem needs PWRKEY low for at least 180ms to power up and at least 500ms to power down.

Manually pushing S1 reliably switches the modem on/off.

Maybe a fix for existing boards could be adding a pullup resistor at the transistor base?


Am 17.11.19 um 02:39 schrieb Craig Leres:
> Maybe this has been discussed and I missed it but occasionally I'll get a module with the modem/simcom stuck in the PoweringOn state. Rebooting does not fix
> this.
> I thought I saw that you could reset the simcom with:
>     power simcom off
>     [wait a minute]
>     power simcom on
> but that doesn't work. I turned up some logging:
>     log monitor
>     log level verbose simcom
> and I see this happen about every 30 seconds:
>     I (2204129) simcom: State timeout, transition to 2
>     I (2204129) simcom: State: Enter PoweringOn state
>     I (2204129) simcom: Power Cycle
> I thought this level of logging would let me see the results of command like:
>     simcom muxtx 3 at+csq
> (signal quality) but I don't see anything after sending it.
> Is there a way to hardware reset the simcom? (Is there any reason this doesn't happen when the ovms module reboots?)
>         Craig
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