Cannot get MC7455 registered on AT&T network


#1

I have an AT&T M2M SIM card which I have used in multiple other modems successfully, but when I try to put it in my MC7455 and connect to the LTE network, I am unsuccessful.

I can see the SIM as online in the AT&T SIM dashboard they provide, and the ppp0 interface obtains an IP address successfully via wvdial, but it doesn’t seem like I am actually registered / connected to the network.

The APN is set correctly and here is the result of a few diagnostic AT commands sent to the modem:

ATIE
Manufacturer: Sierra Wireless, Incorporated
Model: MC7455
Revision: SWI9X30C_02.24.05.06 r7040 CARMD-EV-FRMWR2 2017/05/19 06:23:09
MEID: 35907206237905
IMEI: 359072062379058
IMEI SV: 12
FSN: LQ823242490210
+GCAP: +CGSM


OK
AT+CSQ
+CSQ: 17,99

OK
AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","m2m.com.attz","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0

OK
AT+CGREG?
+CGREG: 0,1

OK

The AT!USBCOMP is set with the bitmask 50D, not sure if that makes a difference, I tried 100D as well and it had the same behavior.

Let me know if you need any more information, or want me to run any additional AT commands.

I’ve exhausted my troubleshooting methods and have scoured the web already, but no solutions I’ve found have been a help.

Thanks in advance.


#2

First, you need to check if the module attaches to the network: AT!GSTATUS? and AT+COPS? will tell. After the module attaches to the network, then next is to establish data session.
USBCOMP 50d presents 2 network interfaces and 3 USB serial ports (AT, NEMA and debug (DM))


#3

I get the following output:

AT!GSTATUS?
!GSTATUS:
Current Time:  9270             Temperature: 36
Reset Counter: 1                Mode:        ONLINE
System mode:   WCDMA            PS state:    Attached
WCDMA band:    WCDMA 850
WCDMA channel: 4384
GMM (PS) state:REGISTERED       NORMAL SERVICE
MM (CS) state: IDLE             NORMAL SERVICE

WCDMA L1 state:L1M_PCH_SLEEP    LAC:         1F3B (7995)
RRC state:   DISCONNECTED       Cell ID:     097E62C3 (159277763)
RxM RSSI C0:   -78              RxD RSSI C0:  ---
RxM RSSI C1:    ---             RxD RSSI C1:  ---


OK
AT+COPS?
+COPS: 0,0,"AT&T",2

OK

#4

AT!GSTATUS? and AT+COPS? result show the module attaches to the WCDMA/UMTS network. AT+CGREG? shows the module is registered to home network. You also mentioned the ppp0 interface obtained IP address, every thing looks OK. So what’s the concern?


#5

I cannot actually send anything over the interface.

ping -I ppp0 8.8.8.8

The above command just times out.

When I disconnect ethernet interface completely and try to solely use ppp0 interface it doesn’t work either.


#6
  1. did you get network interface (ppp0) configured? (ifconfig)
  2. did you set the routing table for 8.8.8.8? (route)
  3. did you try network interface instead of ppp?

#7

Here is what ifconfig shows:

root@igt20:~# ifconfig
eth0      Link encap:Ethernet  HWaddr 78:d0:04:25:4c:17
          inet addr:192.168.1.13  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::7ad0:4ff:fe25:4c17/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST DYNAMIC  MTU:1500  Metric:1
          RX packets:97 errors:0 dropped:0 overruns:0 frame:0
          TX packets:59 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:20753 (20.2 KiB)  TX bytes:6803 (6.6 KiB)
          Interrupt:174

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

ppp0      Link encap:Point-to-Point Protocol
          inet addr:100.71.218.179  P-t-P:10.64.64.64  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:5 errors:0 dropped:0 overruns:0 frame:0
          TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:62 (62.0 B)  TX bytes:645 (645.0 B)

root@igt20:~#

Here is what both “route” and “ip rou” shows (not sure if both prove helpful, not super familiar with routing on Linux):

root@igt20:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         *               0.0.0.0         U     0      0        0 ppp0
default         FIOS_Quantum_Ga 0.0.0.0         UG    0      0        0 eth0
10.64.64.64     *               255.255.255.255 UH    0      0        0 ppp0
192.168.1.0     *               255.255.255.0   U     0      0        0 eth0
FIOS_Quantum_Ga *               255.255.255.255 UH    0      0        0 eth0
root@igt20:~# ip rou
default dev ppp0  scope link
default via 192.168.1.1 dev eth0
10.64.64.64 dev ppp0  proto kernel  scope link  src 100.71.218.179
192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.13
192.168.1.1 dev eth0  scope link
root@igt20:~#

For your last question, what do you mean trying network interface instead of ppp?

Thanks for your help so far.


#8

By the way, I switched from using the AT&T SIM card I was initially trying to the Sierra Wireless smart SIM card we have to see if it makes any difference.

As far as I can tell, I am getting the exact same behavior though.

This is what wvdial shows (I ran this last night):

root@igt20:~# wvdial
--> WvDial: Internet dialer version 1.61
--> Cannot get information for serial port.
--> Initializing modem.
--> Sending: ATZ
ATZ
OK
--> Sending: ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
OK
--> Sending: AT+CGDCONT=1,"IPV4V6","internet.sierrawireless.com"
AT+CGDCONT=1,"IPV4V6","internet.sierrawireless.com"
OK
--> Modem initialized.
--> Sending: ATDT*99***1#
--> Waiting for carrier.
ATDT*99***1#
CONNECT 150000000
--> Carrier detected.  Starting PPP immediately.
--> Starting pppd at Tue Aug 21 18:58:00 2018
--> Pid of pppd: 1877
--> Using interface ppp0
--> pppd: `X▒
--> pppd: `X▒
--> pppd: `X▒
--> pppd: `X▒
--> pppd: `X▒
--> pppd: `X▒
--> local  IP address 100.71.188.140
--> pppd: `X▒
--> remote IP address 10.64.64.64
--> pppd: `X▒
--> primary   DNS address 8.8.8.8
--> pppd: `X▒
--> secondary DNS address 4.2.2.2
--> pppd: `X▒

I did find this forum post in which someone else mentioned that the MC7455 may not work for some carriers with the generic firmware (which I have): no cellular service for em7455 with window10!


#9

@cpmcc94,

Using PPP with the MC’s is perfectly valid but not generally the way people do it as the interface is a little slow of you want max performance, also integrators want to use Ethernet interfaces. Are you using the Sierra Wireless drivers or the open source ones?

You might want to try using the RMNet interface rather than PPP as per the attached document, it say MC73 but is actually applicable to MC74 (and EM75) as well.

1aec569af75a1ab07c66bf85086071fc482f614b.docx (347.1 KB)

Regards

Matt

Regards

Matt