I have done a lot of investigation in to this today and I think I'm
getting somewhere. To start with, here is the log of the AT transactions
by modemmanager:
** Message: (ttyUSB0) opening serial device...
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'ATZ E0 V1 X4 &C1 +CMEE=1<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'ATE0 +CMEE=1<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'AT+CREG=0<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'AT+CFUN=1<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'AT+CPIN?<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>+CPIN:
READY<CR><LF><CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'AT+COPS=0,,<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'AT+CREG?<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>+CREG:
0,5<CR><LF><CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'AT+CGDCONT?<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>+CGDCONT:
1,"IP","telstra.internet","0.0.0.0",0,0<CR><LF><CR><LF>OK<CR><LF>'
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'ATD*99***1#<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>NO CARRIER<CR><LF>'
** (modem-manager:2685): DEBUG: Got failure code 3: No carrier
** (modem-manager:2685): DEBUG: (ttyUSB0): --> 'AT+CEER<CR>'
** (modem-manager:2685): DEBUG: (ttyUSB0): <-- '<CR><LF>+CEER: No cause
information available<CR><LF><CR><LF>OK<CR><LF>'
** Message: (ttyUSB0) closing serial device...
The above consistently fails to connect every time.
I translated the command used above in to a pppd/chat command line:
sudo pppd ttyUSB0 460800 nodetach defaultroute noipdefault noauth lock
usepeerdns connect \
'chat -vs "" "AT" "" \
"ATZ E0 V1 X4 &C1 +CMEE=1" "OK" "ATE0 +CMEE=1" "OK" "AT+CREG=0"
"OK" \
"AT+CFUN=1" "OK" "AT+CPIN?" "OK" "AT+COPS=0,," "OK" "AT+CREG?"
"OK" \
"AT+CGDCONT?" "OK" "ATD*99***1#" \
CONNECT'
The above command fails every time just the same as modemmanager.
I then tried what feels like 1001 variations. I finally found that the
command "AT+COPS=0,," is the problem.
Editing the above command to remove that part works correctly every
time, ie:
sudo pppd ttyUSB0 460800 nodetach defaultroute noipdefault noauth lock
usepeerdns connect \
'chat -vs "" "AT" "" \
"ATZ E0 V1 X4 &C1 +CMEE=1" "OK" "ATE0 +CMEE=1" "OK" "AT+CREG=0"
"OK" \
"AT+CFUN=1" "OK" "AT+CPIN?" "OK" "AT+CREG?" "OK" \
"AT+CGDCONT?" "OK" "ATD*99***1#" \
CONNECT'
>From what I read "AT+COPS=0,," should set the operator selection to automatic.
>You'd think this should be harmless. Unfortunately I think it's this that is
>causing the issue for me and a few others I've seen on forums who seem to have
>the same issue. Also note that the problem is SIM related, as if I put a
>different carriers SIM in the same modem it all works OK.
Is "AT+COPS=0,," necessary? Wouldn't this be the default of a freshly
inserted modem? Can it be commented out of the code?
For completeness, to identify the modem I'm using:
AT+CGMI
huawei
OK
AT+CGMM
K3520
OK
AT+CGMR
11.314.21.31.00
OK
--
Broadband modem fails to connect, no carrier.
https://bugs.launchpad.net/bugs/496834
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