Carrier issue (T-Mobile?)


#1

I have a battery powered Dash that I’m using to send trail temperatures, it then goes into deep sleep for 15 minutes before waking to send the temperature again. After seven months of working just fine it started losing connection. What I found was that this coincided with the network the logs showing it was on T-Mobile. Now the odd thing is doing a power cycle it would connect to T-Mobile, send data just like it should, then after waking from the deep sleep it would appear to send, but Dashboard showed “0 bytes data”. No idea why that would be the case, since the same code with AT&T Mobility always worked.

Contacted Hologram support and the suggestion was to just have the Dash hook to AT&T by getting it’s number and issuing: sendAT("AT+COPS=1,2,“310410"”);
I don’t really understand any of the modem commands/ramifications, but it sounded like I could just program the modem once (i.e. separate program) and then from that point on it would just use that network.

Now I’m not so sure about that. I’ll put the Dash out in the trails, it’ll work fine for a week or two, but then at some point (still plenty of battery) it’ll just quit sending messages. I bring the device home and it won’t connect to a network until I run the program that sets the COPS again.

At this point I don’t know what’s going on or how to even start trying to troubleshoot it. Ideally I’d love to put the modem back to its default behavior and figure out why T-Mobile wasn’t working. The biggest challenge is all these behaviors seem to be related to that particular cell area, when I’m at home it never connects to T-Mobile.


#2

The COPS command should be fairly persistent while the module is powered on but may no not persist across reboot. Your best bet is to start getting familiar with the commands and read relevent sections of the AT command manual. See https://www.u-blox.com/sites/default/files/u-blox-CEL_ATCommands_(UBX-13002752).pdf page 85. Also see page 26 on storing and restoring user settings.

I would recommend building this command into your software on the dash and repeat it whenever the dash boots. You may also want to have your code detect loss of network connectivity and try to re-connect. The modem will try some of this on its own but building in your own provisions will help with reliability.


closed #3

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