EHS6 Modem: TCP PAD Configuration Fails - PDP Context Problem | Telit Cinterion IoT Developer Community
April 14, 2017 - 7:58pm, 8604 views
Dear Group:
What I am trying to do is configure the Gemalto EHS6 wireless modem as a
TCP PAD and Internet client, such that only TCP payload data flows across the
modem serial port once a TCP connection is established. So far I have failed.
A description of the modem configuration and AT commands used follows. (i.e.
Please note that configuration is being done with Hyperterminal on a PC and that
the modem is connected to the PC via its serial port.)
The problem appears to be related to PDP context configuration. Please
advise me of the correct way to configure the modem as a TCP PAD.
I have confirmed that the modem has UMTS network connectivity and the SIM
being used is functional. In addition, the modem is able to receive SMS messages
via the network, and perform basic PDP context operations. The APN used to verify
that is telargo.t-mobile.com and the following AT command was used to configure
the PDP context and APN.
AT+CGDCONT=1,"IP","telargo.t-mobile.com",,0,0
Also, I verified that the Internet server is functional and does not require
authentication.
The AT commands I am using to configure the modem as a TCP PAD and a description of
their use follows.
* Reset the modem to factory settings.
AT&F
* Configure operation on a UMTS network with a GPRS core and the APN.
AT^SICS=0,conType,GPRS0
AT^SICS=0,apn,telargo.t-mobile.com
* Configure transparent service for a UMTS network with UTRAN RAN.
(i.e. Service profile 2.) Note, that substituting "Socket" for "Transparent"
as in the tutorial makes no difference, and I believe that Transparent is
correct. Please advise me if this is wrong.
AT^SISS=2,srvType,"Transparent"
AT^SISS=2,conID,0
* Configure the Internet server address and Port and set 26=Ctrl-Z as the
escape character. I have hard coded the IP address because the modem
doesn't appear to have DNS resolution capability. Is there a way to
configure the modem to perform DNS resolution.
AT^SISS=2,address,"socktcp://10.224.141.12:634;etx=26;timer=300"
* Open Transparent Service. Initially the response is OK but if you
wait for a short period the response is ^SIS: 2,0,94, "PDP: connection failed".
If the command is successful, a TCP connection with the Internet server should
be established at this point.
AT^SISO=2
* Enable Transparent Service. This always fails. If the command is successful,
it should be possible to send and receive TCP payload data via the modem
serial port at this point.
AT^SIST=2
Hello,
So the "PDP: connection failed" is back. And it seems that if PDP cannot be established the network access credentials may not work. Could you explain more about this SMS - is is any special SMS, what does it contain? If PDP cannot be established after receiving it maybe it's some special configuration message from the network which you should apply first. On the other hand does your subscription allow sending and receiving short messages? Maybe not and that could be the reason why the network denies data connection. Generally it seems that you should also ask your network operator about that. It looks like your problem could be operator specific.
What country are you in? Could you also check AT+CGSMS?, ATI1, AT+COPS? commands?
Regards,
Bartłomiej
Hi Bartiomiej:
I discovered why outgoing TCP connections and incoming SMS message reception
are not working at the same time. The problem is that when an SMS message
arrives, it is processed via the default PDP context--number 0, and causes a
PDP context state transition. I believe, but don't know that this occurs locally
rather than in the network and is a Gemalto modem software problem. In any case,
there is an easy way to get around the problem. Basically, just prior to performing
the rest of the SMS configuration, configure a PDP context whose number is
greater than 2 to insure it does not collide with any default PDP contexts.
The following sequence of configuration commands works for me.
* SMS Configuration--Use PDP Context 3
AT+CGDCONT=3,"IP","<APN>",,0,0
AT+CSMS=1
AT+CSMP=17,169,0,0
AT+CNMI=2,1,0,0,0
* TCP Configuration--Use PDP Context 0
AT^SICS=0,conType,GPRS0
AT^SICS=0,apn,<APN>
AT^SISS=2,srvType,"Transparent"
AT^SISS=2,conId,0
AT^SISS=2,address,"socktcp://<IP_ADDRESS>:<TCP_PORT_NO>;etx=26;timer=300"
Best Regards,
Paul R.
Hello,
It is really interesting. But it's good that it's working now.
And what CGSMS settings are you using? Are you using packet domain or circuit switched setting?
Setting of CGDCONT should not be necessary for receiving SMS messages. Could you write what are these SMS'es? Is it just some data for your application or are they sent by the network?
I was not able to reproduce your problem. Could you check ATI1 reply for a firmware version?
Best regards,
Bartłomiej
Hi Bartiomiej:
The modem is using the Packet Domain SMS settings which seems sensible
to me. However, AT+CGSMS reports MO SMS message settings and we are only using
MT SMS messages. If the documentation is correct, these setting are irrelevant.
Please note that the modem is only used to send data via an outgoing TCP
connection, and to receive SMS messages.
The SMS messages are MT and thus definitely sent by the network to our
embedded device--via the modem serial port. Using SMS messages to send small amounts
of data is extremely risky from a security viewpoint. The only real advantage
to using SMS messages is to allow testing from a mobile.
These are the settings you requested.
Cinturion EH6S Version (ATI1)
-----------------------
REVISION 03.001
A-REVISION 00.000.14
Service Type (AT+CGSMS?)
-----------------------
2: Packet Domain Preferred
Best Regards,
Paul R.
Hello,
Thank you for the information.
You are right that AT+CGSMS commands is for mobile originated messages so it should not affect mobile terminated ones. I was not able to test PS messages because my networks don't support this.
The firmware version is at the moment still the latest official release.
Regards,
Bartłomiej