# Serial port device name for USB port



## balanga (Jan 22, 2018)

If I connect a device to a USB port, how do I know how to address it via `cu`?

A couple of my USB modems can be accessed using /dev/cuaU0.0 but a Huawei E3372 (LTE modem) complains about this assignment.


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## aragats (Jan 22, 2018)

Just list them all (`ls -l /dev/cuaU*`) before and after physical connection and compare the output.
In other words, notice the new device name which appears in /dev.
Or maybe I misunderstood your problem?..


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## balanga (Jan 22, 2018)

balanga said:


> If I connect a device to a USB port, how do I know how to address it via `cu`?
> 
> A couple of my USB modems can be accessed using /dev/cuaU0.0 but a Huawei E3372 (LTE modem) complains about this assignment.



On TrueOS I get (/var/log/ppp/log) :-

```
Jan 22 21:25:28  ppp[3016]: Phase: Using interface: tun0
Jan 22 21:25:28  ppp[3016]: Phase: deflink: Created in closed state
Jan 22 21:25:28  ppp[3020]: Phase: PPP Started (ddial mode).
Jan 22 21:25:28  ppp[3020]: Phase: bundle: Establish
Jan 22 21:25:28  ppp[3020]: Phase: deflink: closed -> opening
Jan 22 21:25:28  ppp[3020]: Warning: deflink: /dev/cuaU0.0: Bad file descriptor
Jan 22 21:25:28  ppp[3020]: Phase: deflink: Enter pause (30) for redialing.
Jan 22 21:25:58  ppp[3020]: Warning: deflink: /dev/cuaU0.0: Bad file descriptor
```


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## balanga (Jan 22, 2018)

aragats said:


> Just list them all (`ls -l /dev/cuaU*`) before and after physical connection and compare the output.
> In other words, notice the new device name which appears in /dev.
> Or maybe I misunderstood your problem?..



After booting...
`ls -l /dev/cuaU*`

```
crw-rw----  1 uucp  dialer  0x2d Jan 22 23:09 /dev/cuau2
crw-rw----  1 uucp  dialer  0x2e Jan 22 23:09 /dev/cuau2.init
crw-rw----  1 uucp  dialer  0x2f Jan 22 23:09 /dev/cuau2.lock
```

After inserting Huawei E3372 USB 4G Modem...
`ls -l /dev/cuaU*`

```
crw-rw----  1 uucp  dialer  0xa7 Jan 22 23:11 /dev/cuaU0.0
crw-rw----  1 uucp  dialer  0xa8 Jan 22 23:11 /dev/cuaU0.0.init
crw-rw----  1 uucp  dialer  0xa9 Jan 22 23:11 /dev/cuaU0.0.lock
crw-rw----  1 uucp  dialer  0xad Jan 22 23:11 /dev/cuaU0.1
crw-rw----  1 uucp  dialer  0xae Jan 22 23:11 /dev/cuaU0.1.init
crw-rw----  1 uucp  dialer  0xaf Jan 22 23:11 /dev/cuaU0.1.lock
crw-rw----  1 uucp  dialer  0x2d Jan 22 23:09 /dev/cuau2
crw-rw----  1 uucp  dialer  0x2e Jan 22 23:09 /dev/cuau2.init
crw-rw----  1 uucp  dialer  0x2f Jan 22 23:09 /dev/cuau2.lock
```


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## aragats (Jan 22, 2018)

Didn't you manually set that port in /etc/ppp/ppp.conf? How `ppp` knows its name?
You should be able to see the corresponding device node in /dev, there is no magic out there.

EDIT: you posted before me (-:


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## balanga (Jan 23, 2018)

I'm trying to make some sense from output from my Huawei E3372 USB 4G modem. This is whilst connected to a ThinkPad T420 running FreeBSD 11.1-RELEASE
	
	



```
root@Test:~ # cu -l /dev/cuaU0.0
Connected

^RSSI:17

^HCSQ:"LTE",43,39,106,26

Manufacturer: huawei
Model: E3372
Revision: 21.180.01.00.00
IMEI: 866119027727057
+GCAP: +CGSM,+DS,+ES

OK

^RSSI:17

^HCSQ:"LTE",43,39,111,28

^RSSI:17

^HCSQ:"LTE",43,39,111,26

^RSSI:19

^HCSQ:"LTE",46,39,101,22

^RSSI:16

^HCSQ:"LTE",40,35,106,22

^RSSI:18

^HCSQ:"LTE",44,38,101,22

^RSSI:17

^HCSQ:"LTE",43,38,106,24

^RSSI:17

^HCSQ:"LTE",43,38,91,24

^RSSI:17

^HCSQ:"LTE",43,38,106,26
```

I've been struggling to get this modem working with FreeBSD for over a year, following various guides but have yet to find an effective solution. Having got 2 USB 3G modems working with PPP on FreeBSD recently, I tried the same /etc/ppp/ppp.conf file but it doesn't work. It works effortlessly on Debian, and I would copy the configuration file to FreeBSD if I could find it.

On FreeBSD I sometimes get 
	
	



```
Warning: deflink: /dev/cuau1: Bad file descriptor
```
...no idea why...


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