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

[Michael Balzer]

Craig, Mark,

I just stumbled upon a misreading from my side:

I had accidentally taken the v3.0 schematics of the main board for reference, that only had pull-ups on ports 1 & 2. There was a change in v3.1 adding pull-up
resistors on ports 0 & 3 as well.

So with a 3.1/3.2 module, there actually is a 10K pullup on both MDM_EN and MDM_DTR, before the transistor.

With that 10K, we have this transistor control:



That should result in ~1.5V at the base on MDM_EN high, enough for the transistor to switch, so I don't know what's going wrong here.

You can access both pullups from the side, they are located left of the S2 switch on the main board. R8 is on MDM_EN, R9 on MDM_DTR. R8 shows that very short
rise in voltage on transition to high, while R9 shows the expected behaviour of a constant +3.3 when the port is high.

Regards,
Michael


Am 18.11.19 um 02:47 schrieb Mark Webb-Johnson:
> I don’t think that circuit has changed since the very first v1 of OVMS. Maybe we have been lucky in the past with the timing?
>
> I will discuss it with the manufacturer, as that part of the circuit is his design and he should know the thinking behind it the best.
>
> Our intention it have EGPIO #0 able to control the PWRKEY of the modem - so as to be able to power it up/down under program control. We are not really controlling the power to the modem - more telling the modem to control itself.
>
> Regards, Mark.
>
>> On 17 Nov 2019, at 8:11 PM, Michael Balzer <dexter at expeedo.de> wrote:
>>
>> 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?
>>
>> Regards,
>> Michael
>>
>>
>> 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
>>> _______________________________________________
>>> OvmsDev mailing list
>>> OvmsDev at lists.openvehicles.com
>>> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
>> -- 
>> Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
>> Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
>>
>>
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-- 
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26

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