Help choosing modem firmware for WP7702 (ULPM problems too?)

I’m confused about which modem firmware I should be using with the WP7702 (R12). I’m using Hologram SIM cards. In my area in the United States, these Hologram cards typically connect to AT&T on LTE or T-Mobile on 2G.

Hologram isn’t a carrier – so which carrier firmware should I pick? I’m using the modem firmware SPK files on this page: https://source.sierrawireless.com/resources/airprime/software/wp77xx/wp77xx-firmware-latest-release-components/#sthash.74J2zVN6.dpbs

Sierra firmware

  • Connects fine to AT&T LTE and T-Mobile 2G
  • On LTE, pmtool shutdown prints “Initiated shutdown of MDM” and does nothing, looks like it’s enabling PSM so I have to do AT+CPSMS=0 afterward, then it will shut down. On 2G it works without the CPSMS stuff.
  • AT!POWERMODE=3 works and bypasses the CPSMS problem on LTE

AT&T firmware

  • Connects fine to AT&T LTE and T-Mobile 2G
  • On LTE, pmtool shutdown prints “Initiated shutdown of MDM” and does nothing, looks like it’s enabling PSM so I have to do AT+CPSMS=0 afterward, then it will shut down. On 2G it works without the CPSMS stuff.
  • AT!POWERMODE=3 returns ERROR.

Verizon firmware

  • Connects fine to T-Mobile 2G. Doesn’t seem to work with LTE, not even Verizon’s network. This might be Hologram’s fault.
  • pmtool shutdown seems to work, even without needing to disable PSM. Probably because it’s not connected on LTE.
  • AT!POWERMODE=3 returns ERROR.

Generic PTCRB firmware

  • Doesn’t connect to any networks. Neither LTE nor GSM.
  • pmtool shutdown seems to work, even without needing to disable PSM. Probably because it’s not connected on LTE.
  • AT!POWERMODE=3 returns ERROR.

Generic GCF firmware

  • Doesn’t connect to any networks. Neither LTE nor GSM.
  • pmtool shutdown seems to work, even without needing to disable PSM. Probably because it’s not connected on LTE.
  • AT!POWERMODE=3 works.

In general, it looks like I’m not allowed to use AT!POWERMODE at all on most firmwares, with the exception of Sierra’s firmware and the GCF firmware. In the firmwares where I’m not allowed to use it, even AT!POWERMODE? returns ERROR. It looks like the “auto PSM enabling” preventing ULPM until I do AT+CPSMS=0 is dependent on whether I’m connected on an LTE network or not. On GSM it doesn’t happen but on LTE it does.

Logically based on these results, it seems like I have to pick either the Sierra firmware or the AT&T firmware. Is the Sierra firmware only meant for Sierra SIMs? Is it even okay for me to use that firmware with a Hologram SIM? It works…but am I technically doing something wrong by using it? What about shipping internationally? Would I need to switch to GCF firmware for international units? Is it normal that I can’t seem to use the generic firmware (GCF/PTCRB) properly in the USA?

Any insight would be much appreciated. My head feels like it’s spinning after doing all these tests.

Hi @doug,
Which is error code showed when the module fails to connect LTE and GSM when it runs on Generic GCF and PTCRB firmwares. Could you please help to check creg and cereg status by command
at+creg?
at+cereg?
The response code will show the reason and help understand the situation
Thanks

Hi @Vianney,

Thanks for your reply. It never seems to register with a network on the PTCRB or GCF firmwares. Here is the output with the GCF firmware:

AT+CREG?
+CREG: 2,2

OK
AT+CEREG?
+CEREG: 2,2

OK

Here is the output of cm radio:

root@swi-mdm9x28-wp:~# cm radio
Power:                         ON
Current Network Operator:      
Current RAT:                   Module not registered on network, RAT not available
Status:                        Not registered and not currently searching for new operator (LE_MRC_REG_NONE)
Signal:                        No signal strength (0)
PS:                            Packet Switched Not registered (LE_MRC_REG_NONE)

While writing this reply, I tried to do AT+COPS=? to get a list of operators, and that seemed to hang for a really long time. I didn’t time it, but it was probably about 5 minutes. It finally returned:

+COPS: (1,"T-Mobile","T-Mobile","310260",0),,(0,1,2,3,4),(0,1,2)

…and then I noticed it had finally connected to AT&T’s LTE network:

root@swi-mdm9x28-wp:~# cm radio
Power:                         ON
Current Network Operator:      AT&T
Current RAT:                   LTE network (LE_MRC_RAT_LTE)
Status:                        Registered to a roaming network (LE_MRC_REG_ROAMING)
Signal:                        Weak signal strength (2)
PS:                            Packet Switched Registered to a roaming network (LE_MRC_REG_ROAMING)

Hmm…any idea why it takes so much longer to make an initial connection with the GCF firmware? It takes forever, whereas the AT&T or Sierra firmwares basically immediately connect. And why didn’t the +COPS response return any LTE networks even though it connected to AT&T? I tried the command again and Verizon showed up…but still no AT&T even though I’m connected to it:

+COPS: (1,"T-Mobile","T-Mobile","310260",0),(3,"Verizon","Verizon","311480",9),,(0,1,2,3,4),(0,1,2)

Weird…now, even after a reboot, everything seems fine and it connects very quickly. But right after flashing the GCF firmware, it took a really long time. Also, if I restrict it to only connect to 2G, it connects to T-Mobile fast, but then if I restrict it back to LTE, it takes forever again. As I’m writing this message, it hasn’t found AT&T’s LTE network again yet, and it’s been searching for about 10 minutes. This kind of a delay for finding an LTE network to connect to seems like it could be problematic for us in the field…

Edit: 20 minutes later, it still hasn’t discovered AT&T’s LTE network. I’m starting to wonder if my initial AT+COPS=? command might have kickstarted something that doesn’t automatically happen otherwise.

Hi @doug,
Why it takes so much longer to make an initial connection with the GCF firmware.

  • As you know Generic firmware includes information of supported operators (AT&T, Verizon,Sierra, T-Mobile). It wastes time to go through that data, get properly AT&T operator then attach network. It is the reason it takes longer than AT&T firmware which just has its info. In other hands, WP7702 supports a lot of bands (14 bands) so the module takes time to check each band. I have a workaround for this case. You can force band which your operator (AT&T) is using. At that time, it will return faster. Please follow:

Check supported bands:

at!band?

Index, Name, GW Band Mask L Band Mask 1 TDS Band Mask L Band Mask 2
00, All bands, 0000000000280180 000000000A0F189F 0000000000000000 0000000000000000

OK
This value shows the module is setting all bands.

Check operating bands

at*psrdbs=?

*PSRDBS: (0-1),(1,2,8,16,131072,262144,524288,1048576,2097152,16777216,268435456,536870912,8589934592,17179869184,34359738368,68719476736,4398046511104,17592186044416)

OK

It will show Operating bands. Let select the band which your operator is using
Ex: Set my module to LTE Band 5

at*psrdbs=1,2097152

OK

Then check band again. At this time, our module use band 5 only

at!band?
Index, Name, GW Band Mask L Band Mask 1 TDS Band Mask L Band Mask 2
01, User bands, 0000000000000000 0000000000000010 0000000000000000 0000000000000000

OK

Then, check at+cops=?. Module will return faster
Note, when you set all bands, at+cops=? command will not return to the operator which your module is connecting to. That is reason you don’t see AT&T in list
Let feel free share me any concern and tick “Solution” if your question is answered
Thanks

Hi @Vianney,

I appreciate your response and your explanation. I’m sorry for taking so long to write back. I’m simultaneously dealing with several issues. Is it really normal for the WP7702 to take about an hour to find AT&T for the first time though? I actually timed it today – it took somewhere between 40 to 70 minutes to find AT&T. That seems excessive even for checking all the bands. Am I wrong?

I’m concerned about sending these out in the field. The workaround you described above sounds like it could help us find AT&T’s network here initially for testing, but after that point, this device could go anywhere in the USA, and any country eventually. I won’t have any idea which bands will be in use in those areas. I wouldn’t want to restrict the bands in that case.

I also kind of feel like my original question wasn’t answered…which firmware should I be using for a connection through Hologram? Are the PTCRB/GCF firmwares more appropriate? Is the Sierra firmware exclusively for Sierra’s own data plan? Also, why doesn’t AT!POWERMODE work on every firmware?

Thanks!
Doug

Hi @doug,
So to answer your questions first:

  • Is it really normal for the WP7702 to take about an hour to find AT&T for the first time though?
    It is NOT normal. I tried using a non-Hologram SIM to attach the network. It takes about 1-2 mins (in case all bands are set) to attach the network. Have you tried to use an AT&T SIM to attach the network while using CGF firmware? How is the result? Is it faster? If yes, the issue may be caused by Hologram site
  • For the issue AT!POWERMODE doesn’t work on some FWs. That is a bug I have raised a ticket to Sierra. They will resolve and deliver fixed in further.
  • In the current situation, I just say that you can use Sierra FW. It will be NOT locked network registration and AT!POWER
    Please feel free if you have any concern and help us tick Solution if your question is answered
    Thanks

Hi @Vianney,

Thanks. The Sierra FW definitely works faster, so I may end up using it. With the GCF firmware, it looks like one thing that really helps with registration time is disabling NB-IoT. I will also also look into restricting the bands to North America bands using the commands you suggested above.

Thanks for the explanation of the other issues. I’m assuming they are also aware of the issue I raised in this post where pmtool shutdown doesn’t work until I do AT+CPSMS=0 afterward?