Cat M1 connection fails on Linux

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fhunleth's picture
fhunleth
Junior(0)

I'm working through the Raspberry Pi 3 getting started guide, but on a Linux PC and having trouble. This is for the AT&T Starter Kit with the WNC M14A2A module. The Ethernet interface has a 10.0.0.x address, so my understanding is that it's not connected:

$ ifconfig enx001122334456
enx001122334456 Link encap:Ethernet HWaddr 00:11:22:33:44:56
inet addr:10.0.0.10 Bcast:10.0.0.255 Mask:255.255.255.0
inet6 addr: fe80::1217:6946:1d9a:c6a2/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:34 errors:0 dropped:0 overruns:0 frame:0
TX packets:370 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2659 (2.6 KB) TX bytes:89238 (89.2 KB)

I then looked at the troubleshooting section (appendix D) to try to debug. Here's a log:

$ picocom /dev/ttyACM0
ATE1
OK
AT%PDNSET?
%PDNSET: 1,m2m.com.attz,IP,,,,,0,0,0
AT+CSQ
+CSQ: 99,99
OK
AT+CPIN?
+CPIN: READY
OK
AT+CREG?
+CREG: 0,2
OK
ATI
Manufacturer: WNC
Model: IMA3
Revision: MPSS: IMA3_v10.58.174043 APSS: IMA3_v10.52.174043

I've registered the SIM card, but I don't think that it's even connecting to the AT&T network. I've also tried a few antennas. I'm in a major metro area on the east coast, so I should have a pretty good signal.

Does anyone have other ideas to try?

Thanks,
Frank

LightCollector's picture
LightCollector
Moderator(20)

Hi,

 

The LTE Add-On kit for the Pi definately works with the LTE Cat1 firmware.  You indicate you are using the LTE-M firmware with a Pi or a Linux PC?  In either case it looks like your USB ethernet interface is working.  I'm assuming the 14A2A shield has never been used and connected before...

 

Is your SIM card activated? After registering the card and entering various info you have to take an additional step and activate the card.  You can verify and debug the connectivity through the ATT control center account.  It shows the activated state of the SIM and whether your device is connected or not.

 

Best regards

fhunleth's picture
fhunleth
Junior(0)

Thanks for the quick response.

I'm currently trying everything on with a Linux PC rather than a Pi, but I really don't think there's anything Pi-specific in the instructions so far. You're right that the 14A2A shield hasn't been used or connected before. The USB ethernet interface is working fine: DHCP always returns 10.0.0.10 and I can ping 10.0.0.1 reliably. I can't ping 8.8.8.8.

The SIM card is activated. I went to the ATT control center and it reports that the device isn't in session. However, apparently the device was in session last night and that 600KB was transferred. I have no clue how that happened, but I certainly haven't been able to reproduce today. It must have connected when I was trying it out, but I certainly didn't notice.

I think that I'm at the same place I was earlier in not knowing how to debug. I've double checked that the ICCID was entered correctly, and run through the steps in the guide like I've done before. As far as I can tell, the AT&T control center diagnostics are just telling me that the device isn't connected to the network.

Any other ideas?

Thanks again,
Frank

fhunleth's picture
fhunleth
Junior(0)

Update:
If I move the SIM card to another manufacturer's CAT M1 board, I'm able to connect. It takes between 10-15 minutes to connect, but it seems to work consistently. I can't seem to get it to connect again with the 14A2A shield, though.

I'm wondering if it's just that I have a very low signal even though I'm in a fairly dense urban area. I had thought that the technology was such that if Cat 1 worked well that Cat M1 would be fine. Could anyone confirm this?

Unless I see suggestions, I think that my next step is to update the firmware on the shield to switch it to a Cat 1 device and retry my experiments.

LightCollector's picture
LightCollector
Moderator(20)

Sounds like you're making some good progress debugging it.  The fact that you saw some traffic from the 14A2A confuses things but if it saw some, it does mean it's working at least somewhat.

 

What you say about the signal level... Well it is theoretically true that the M1 waveform should work with a smaller signal.  The M1 waveform only uses 1 antenna (the primary), Cat 1 works much better with 2.   However it's not clear if the M1 towers and the 14A2A are working optimally.  This is ATT's first rollout of M1 it is not really proven yet if it works the way the whitepapers and marketing say they should ;-)  The other factor is that just because they have full LTE signal doesn't mean they have good M1 support where you are.  I am unaware of any maps to back that up or refute that I do know from what ATT said that M1 is not yet everywhere.

 

You could still try to return the 14A2A for another or just order a 2nd one and try it too.  Which other modem does the ATT sim work with?

 

Best regards

fhunleth's picture
fhunleth
Junior(0)

We have a second 14A2A that we'll try in a different city to see if that makes a difference. I'll report back on that experiment.

As for the other modem, it's a Quectel BG96MA. Here's the info I got when I connected:

AT+QNWINFO
+QNWINFO: "CAT-M1","310410","LTE BAND 12",5110 

I was hoping that there'd be a way to find the latitude/longitude for the tower so that I could get an idea how far away it was. I didn't see a command to do that though.

 

Thanks again for you help,
Frank

LightCollector's picture
LightCollector
Moderator(20)

Hi Frank,  Sorry I can't help more yet.  I hope it works for you, let me know.

 

I know Avnet distributes the other module.  Who makes the dev board you are using, the Quectel one?

 

One additional thought, you may be able to use AT+CSQ to get an RSSI/BER type reading on that other module.  I'm not sure, I haven't looked at its AT command guide.  There are other ways to get LTE signal quailty (RSSI is not very telling) measurements but I do know that some of that seems broken on the 14A2A.  The AT+CSQ cmd on the 14A2A "should" work still though.  The Quectel module's variant of that may tell you something.

 

Best regards