[Ovmsdev] Car lost GPRS connection notification

Mark Webb-Johnson mark at webb-johnson.net
Tue May 15 13:48:46 HKT 2012


Supporting SMS would mean having to do this from the car, which is much more tricky (particular if you want to control time of day for notifications).

Doing this in the car would mean we could SMS but not PUSH notify. Doing it on the server would mean we could PUSH notify but not SMS.

I didn't really want to do this in the car because what if the car lost network connectivity? We can't issue the SMS.

In theory, we can do SMS from the server, but that means paid plans and the server needing to know contact telephone numbers - which is messy.

Regards, Mark.

On 15 May, 2012, at 1:36 PM, Tom Saxton wrote:

> I think it's a great idea and would like to have it. I generally leave push
> turned off to reduce battery usage, so I'd prefer a text message.
> I'm thinking of being on the road, charging in some rural area with spotty
> coverage, and expecting that if the charge gets interrupted (unplugged, pops
> the breaker, whatever), then I'll get a text message. If the cars loses the
> connection, I'd like to be notified of that promptly so I know I need to
> check on the car.
> I would want to selectively enable, as I don't want a text message in the
> middle of the night if the car loses the connection while in our garage.
>    Tom
> on 5/14/12 10:14 PM, Mark Webb-Johnson wrote:
>> Rafael has suggested that we add a car-lost-gprs-connection notification to
>> the OVMS system. The idea being that when your car loses GPRS connection
>> (cellular coverage, fault, whatever), you get a notification to your app to
>> let you know. And, presumably, another notification should it come back.
>> It is common for a car to lose cellular connection for a minute or so, then
>> re-establish.
>> It is also reasonably common to lose connectivity when the GSM signal is lost.
>> It does seem a nice idea, and not too hard to do.
>> The way it would work would be to have a threshold in the server. A
>> notification time, presumably in seconds.
>> If a car disconnected (or 20 minute timeout was force disconnected), we would
>> put a record in a pending table, timestamped NOW()+thresholdseconds.
>> If the car connected, and the pending table has a record for that car, we
>> would just remove the record.
>> If the car connected, and there was no pending table record for that car, we
>> would send a push notification for all apps on that car to tell them that the
>> car is connected.
>> Periodically, we check the pending table and if any records have timed out, we
>> (a) send a push notification for all the apps on that car to tell them that
>> the car has disconnected, and (b) remove the record.
>> The result of this is that if the car disconnects for a short time, then
>> reconnects, no notification is raised. But, if the car disconnects for a long
>> time, you get a notification both when we find it has disconnected and when we
>> see it reconnect. This can all be done from the server, irrespective of
>> version of firmware in the car/apps.
>> The questions are: (a) what do people think, (b) what should a reasonable
>> timeout be, and (c) could this be _on_ for everyone.
>> Would anyone here _not_ want this?
>> I would suggest a reasonable timeout, to alert after, would be an hour or so.
>> It is easier to code this if it is universally on for everyone - we can just
>> have a single timeout in the server. If we want individual control, we'd have
>> to have a setting per-vehicle and provide the users a mechanism to change that
>> setting. That would be much more work.
>> Regards, Mark.
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