EP06-A, EM06-A, SMS PDU mode, and AT+CMGL

In the process of sorting a completely unrelated issue, I believe we have stumbled across what may be an error in the firmware implementation of AT+CMGL in PDU mode. We have reproduced the problem on multiple modems of these two models, running on different LTE service providers (so, provider MBN files less likely to be implemented).

With no SMS currently stored in memory, in PDU mode (AT+CMGF? verified returns 0), we expect:

AT+CMGL=4
OK

Observed behavior:

AT+CMGF?
+CMGF: 0
OK
AT+CMGL=4
+CMS ERROR: 303

Additional behaviors we can see around this behavior:

AT+CMGF=0
OK
AT+CMGL=?
+CMGL: (“REC UNREAD”,“REC READ”,“STO UNSENT”,“STO SENT”,“ALL”)
OK
AT+CMGF=1
OK
AT+CMGL=?
+CMGL: (“REC UNREAD”,“REC READ”,“STO UNSENT”,“STO SENT”,“ALL”)
OK

Instead, we expected to see (from an EP06-E):

AT+CMGF?
+CMGF: 0
OK
AT+CMGL=?
+CMGL: (0-4)
OK
AT+CMGF=1
OK
AT+CMGL=?
+CMGL: (“REC UNREAD”,“REC READ”,“STO UNSENT”,“STO SENT”,“ALL”)
OK

Essentially, when SMS format is text mode, the command works normally (and we can send and receive texts using text mode). We can bulk read messages from memory using AT+CMGL=“ALL” and get the expected results. However, if we switch to PDU mode, the behavior of AT+CMGL does not appear to switch modes properly, and our attempts to perform a bulk read in the same way fail with the error message shown above.

So far, the following firmwares we have in our possession are confirmed affected:

EP06ALAR02A07M4G
EM06ALAR03A05M4G

Is this a known issue? We thought we might be crazy for the last few days, when we stumbled upon this while working on this unrelated issue. We waited to inquire until we were able to have several other people with EP06-A or EM06-A on other networks (without Verizon MBN active) confirm.

Thank you!

Hi,
Thanks for your query in Quectel forums.
May I ask which module and version you have the problem with PDU? It is possible for me to test EM06ALAR03A05M4G locally. there is no problem,The test content is as follows:
[2021-02-20_09:24:32:275]AT+CMGF?

[2021-02-20_09:24:32:275]+CMGF: 1

[2021-02-20_09:24:32:275]OK
[2021-02-20_09:24:39:568]AT+CMGL=?

[2021-02-20_09:24:39:570]+CMGL: (“REC UNREAD”,“REC READ”,“STO UNSENT”,“STO SENT”,“ALL”)

[2021-02-20_09:24:39:570]OK
[2021-02-20_09:24:50:892]ATI

[2021-02-20_09:24:50:892]Quectel
[2021-02-20_09:24:50:892]EM06
[2021-02-20_09:24:50:892]Revision: EM06ALAR03A05M4G

[2021-02-20_09:24:50:892]OK
[2021-02-20_09:25:08:036]AT+CMGF=?

[2021-02-20_09:25:08:036]+CMGF: (0,1)

[2021-02-20_09:25:08:036]OK
[2021-02-20_09:25:11:008]AT+CMGF=0

[2021-02-20_09:25:11:008]OK
[2021-02-20_09:25:18:847]AT+CMGL=?

[2021-02-20_09:25:18:847]+CMGL: (0-4)

[2021-02-20_09:25:18:847]OK
[2021-02-20_09:25:50:615]AT+CMGF?

[2021-02-20_09:25:50:615]+CMGF: 0

[2021-02-20_09:25:50:615]OK
[2021-02-20_09:25:57:186]AT+CMGL=4

[2021-02-20_09:25:57:190]OK

thanks.

From above, we’ve found this so far on the following firmwares:

However, we’ve found new information since yesterday. We have one modem with EP06ALAR02A07M4G that is working normally, example:

AT+CMGL=4
+CMGL: 0,1,55
07914150740250F62006C942444400001220912283244A2CD9775D0E6A96E7F3B2FB5C9683EC6579DA9C1E87E9E9B71B347E93CBA0F41C746CDD7234DC8C06
+CMGL: 1,1,55
07914150740250F62406C942444400001220912283344A2CD9775D0E6A96E7F3B2FB5C9683EC6579DA9C1E87E9E9B71B347E93CBA0F41C746CC566305B2C07
AT+GMR
EP06ALAR02A07M4G

So far the only difference we have found is that the three modems which produce the original error (AT+CMGL=4 not working in PDU mode) have SIMs with no on-board message memory. The working line sim shown here does have on-board memory. For what it’s worth, the modems producing the error do have CPMS set to ME, and we are working with ME storage and not attempting to work with the non-existant SM storage on those units.

We have also seen this error yesterday on firmware EP06ALAR02A04M4G, but are still trying to determine if it fits the pattern, as checking for on board sim slots is also returning an error on that specific modem:

AT+GMR
EP06ALAR02A04M4G
OK
AT+CPMS?
+CMS ERROR: 350
TIMEOUT ERROR

However, I would not consider that report reliable yet, as we are still working to verify that everything else on that modem seems normal.

Hi,
Thanks for your query in Quectel forums.
Your current version is too old, hope you can verify on the latest version, thank you.

[2021-02-22_16:32:11:343]
[2021-02-22_16:32:11:343]+CFUN: 1

[2021-02-22_16:32:11:343]+CPIN: READY

[2021-02-22_16:32:11:343]+QUSIM: 1

[2021-02-22_16:32:11:343]+QIND: SMS DONE

[2021-02-22_16:32:11:343]+QIND: PB DONE
[2021-02-22_16:32:11:343]ati

[2021-02-22_16:32:11:343]Quectel
[2021-02-22_16:32:11:343]EP06
[2021-02-22_16:32:11:343]Revision: EP06ALAR02A08M4G

[2021-02-22_16:32:11:343]OK
[2021-02-22_16:32:27:019]at+cpms?

[2021-02-22_16:32:27:023]+CPMS: “ME”,0,255,“ME”,0,255,“ME”,0,255

[2021-02-22_16:32:27:023]OK