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Can't send SMS messages using a GSM/GPRS module

pawelmoll
1: Seeker

Hi! I've just got a V-Sim and activated it to use with a small development board using Quectel MC20 GSM/GPRS module. Generally speaking everything works fine, I can activate GPRS context, open TCP connections etc. One small problem I've got is with sending SMS messages...

 

The module receives messages from the V app (aka "commands") - I can read them all right. But when I try sending a message, I get "CMS ERROR: 21", like this:

 

AT+CMSS=1
+CMS ERROR: 21
AT+CMSS=3
+CMS ERROR: 21

In the above example I've tried sending the message to both my normal (non-Vodafone) UK number, and to the slightly weird "123456" I get the "app commands" from:

 

AT+CMGL="ALL"
+CMGL: 1,"STO UNSENT","07xxxxxxxxx","",,129,20
TestToNormalUKNumber

+CMGL: 2,"REC READ","123456","","2019/10/13 23:52:06+08",128,18
TestCommandFromApp

+CMGL: 3,"STO UNSENT","123456","",,129,12
TestTo123456 OK

Perhaps the plan I've chosen ("Generic Tracker" as that's what the device I'm prototyping is supposed to be) doesn't allow me to send SMS messages at all? If so, which one should I switch to in order to be able to do so? It's not a crucial functionality for that little project, but I simply don't like not understanding what's going on 🙂

 

One thing I've noticed is that the device reports it status as "Registered, roaming":

AT+CREG?
+CREG: 0,5

OK

so perhaps that's why the SMSC number

AT+CSCA?
+CSCA: "+316540967011",145

OK

looks Dutch? Or perhaps I simply somehow got it wrong and that's why my outgoing messages are failed? The CMS error 21 is documented as "Invalid index" which doesn't tell me much... Note that when I changed SMSC to Vodafone UK's (+447785016005), I was getting CMS error 28:

AT+CSCA="+447785016005",145
OK
AT+CMSS=1
+CMS ERROR: 28

which seems to mean "Unidentified subscriber" - that would suggest that indeed V-Sim is not really considered a Vodafone UK subscriber module...

 

So, am I doing something wrong, am I missing something, or is this the "correct behaviour"?

 

Regards and thanks for any help!

4 REPLIES 4

Vtomanov
2: Seeker
2: Seeker

What AON settings you use ?

alexchris
1: Seeker

Thanks for the info, I'm getting same issues with an oldish Arduino GSM Shield SIM900 with a v-sim, i chose to activate as car tracker. Just get "ERROR" when setting the SMS destination number, and have tried setting the message center as you suggested too but made no difference. Seems the SIM has a strange "number", so guess can't be used in the normal way?  Using the V by Vodafone App I attempted to send message to the sim but even these fail!

 

Used some of the code from here https://lastminuteengineers.com/sim900-gsm-shield-arduino-tutorial/ changing serial port speed from 9600 to 19200 for my particular shield for my testing, haven't tried in a phone yet (but that would be my next step). I know there are some reported issues with them blocking some IMEI numbers as some of these devices have generic ones or those they won't allow according to other reports I've seen on Amazon.

 

My GSM shield works fine with a GiffGaff UK Sim by the way, for £2 more a month (£6 on minimum PAYG contract) looks like I'll be using that instead, as you can also make/receive calls etc and it has a UK mobile number.

I should add mine gets

AT+CREG?
CREG: 1,2

So doesn't look like the SIM has actually registered in the SIM900 device.

Just an update, after leaving the SIM in device for a hour or so (card was only activated today via the v by vodafone app) the SIM became registered. I had tinkered with some of the AT commands and got

+COPS: 0,0,"vodafone UK" and a test text message came through from the v by vodafone app. Still further testing to do, not sure if it would be able to send or receive via other than the v by vodafone app though so no good for a tracker if you need to send SMS to it to do stuff.

 

+CREG: 1,5