SIMCom SIM7906 LTE modem disconnecting/detaching on SG-3100

Filemon

I'm unclear; so without a ppp connection configured to use the modem it still shows as the USB device disconnecting regularly?

If the PPP interface was disabled before changing the "kmem_size_max" (about two months ago), the modem's USB device was disconnecting constantly.
I disabled the PPP interface again today and the modem wasn't disconnecting. I presume, it's because the "kmem_size_max" was modified.

stephenw10

Ok, well with the ppp connection disabled you should be able to connect to the at interface and query the modem and see the uptime.
Potentially you might be able to see and logs there if it is rebooting.

Filemon

@stephenw10
Only now I have some time to get back to this.
I upgraded to 23.09 and the situation is even worse.
If the ppp interface is enabled, the modem disconnects 10-15 times daily.
If I disable the ppp interface, it disconnects constantly.

Some sample output:

# cu -l /dev/cuaU0.1
Connected
$GNGNS,,,,,,NNN,,,,,,*1D
$GPVTG,,T,,M,,N,,K,N*2C
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GNGSA,A,1,,,,,,,,,,,,,,,*00
$BDGSA,A,1,,,,,,,,,,,,,,,*0F
$GPGGA,,,,,,0,,,,,,,,*66
$PQXFI,,,,,,,,,,*56
$GPRMC,,V,,,,,,,,,,N*53
$GNGNS,,,,,,NNN,,,,,,*1D
$GPVTG,,T,,M,,N,,K,N*2C
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GNGSA,A,1,,,,,,,,,,,,,,,*00
$BDGSA,A,1,,,,,,,,,,,,,,,*0F
$GPGGA,,,,,,0,,,,,,,,*66
$PQXFI,,,,,,,,,,*56
$GPRMC,,V,,,,,,,,,,N*53
$GNGNS,,,,,,NNN,,,,,,*1D
$GPVTG,,T,,M,,N,,K,N*2C
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GNGSA,A,1,,,,,,,,,,,,,,,*00
$BDGSA,A,1,,,,,,,,,,,,,,,*0F
$GPGGA,,,,,,0,,,,,,,,*66
$PQXFI,,,,,,,,,,*56
$GPRMC,,V,,,,,,,,,,N*53
$GNGNS,,,,,,NNN,,,,,,*1D
$GPVTG,,T,,M,,N,,K,N*2C
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GNGSA,A,1,,,,,,,,,,,,,,,*00
$BDGSA,A,1,,,,,,,,,,,,,,,*0F
$GPGGA,,,,,,0,,,,,,,,*66
$PQXFI,,,,,,,,,,*56
$GPRMC,,V,,,,,,,,,,N*53
<disconnect here>
#

# cu -l /dev/cuaU0.2
Connected

+CPIN: READY

PB DONE
<disconnect here>

# cu -l /dev/cuaU0.3
Connected

+CPIN: READY

PB DONE
<disconnect here>

I've been trying to find that uptime, but with no luck.
This is a manual for SIMCom 7000 series - https://cdn.geekfactory.mx/sim7000g/SIM7000%20Series_AT%20Command%20Manual_V1.06.pdf.
Any ideas, what AT commands to use?

stephenw10

Are you entering anything at those interfaces to get that output?
cuaU0.1 is a GPS interface so not that.
Both the other look like AT though. If you enter at it should return OK.

Filemon

@stephenw10
That is a response from the modem.
But I can enter AT commands.
For instance

**AT+CBC**
+CBC: 3.302V

**AT+CPMUTEMP**
+CPMUTEMP: 46

But there is only 3-5 seconds to enter a command before the modem detaches and the cu connection is lost.

Plus, there are hundreds of commands and I don't know what to look for there.

stephenw10

If the modem detaches from the USB subsystem even when PPP is not running it's hard to see how that could be anything other than the modem rebooting.

One of the status commands probably shows uptime. I don't have that modem to test though.

How long does it take before you can reconnect to it after it detaches?

Filemon

@stephenw10
It's exactly six seconds between "kernel: u3g0: detached" and "kernel: u3g0: Found 6 ports."

stephenw10

Can you connect right away though? If the modem is rebooting I'd expect it to not respond for a time.

Filemon

@stephenw10

# cu -l /dev/cuaU0.3
Connected    (<- this message is shown immediately)

+CPIN: READY

PB DONE
(but it takes about 17-18 seconds to get to here, where AT commands can be enetered)

stephenw10

A Sierra modem in a 2100 here will show the time since boot in seconds in the modem status output:

at!gstatus?
!GSTATUS: 
Current Time:  1093247		Temperature: 39
Bootup Time:   0		Mode:        ONLINE         
System mode:   LTE        	PS state:    Attached     
LTE band:      B3     		LTE bw:      15 MHz  
LTE Rx chan:   1392		LTE Tx chan: 19392
EMM state:     Registered     	Normal Service 
RRC state:     RRC Idle       
IMS reg state: No Srv  		

RSSI (dBm):    -59		Tx Power:    0
RSRP (dBm):    -88		TAC:         048C (1164)
RSRQ (dB):     -11		Cell ID:     000E0F02 (921346)
SINR (dB):      5.2


OK

Can you test the modem in something else?

Filemon

@stephenw10 said in SIMCom SIM7906 LTE modem disconnecting/detaching on SG-3100:

Can you test the modem in something else?

I'll do it, when I get back to the office after the weekend.