restart wlan9

[PaddyB]

generally, ifconfig wlan9 up works, but not in my special case:

I use the onboard wifi both to connect to the internet ( wlan0, 192.168.0.0/24 at least here at home) and to provide an AP ( wlan9, 10.10.10.0/24), where for example the wind sensor (10.10.10.72)  is connected.

after some time, wlan0 still works fine, but wlan9 is gone, and i cannot restart it.  I booted the Pi last evening, and it was recording wind data via wlan9 for ~ 10h, but then it stopped around 0605 this morning. 

The windsensor (yachta) is just fine, and switched back to internal AP mode, when it lost the connection to the PI.

Code:

root@openplotter:~# ping -c 3 10.10.10.72
PING 10.10.10.72 (10.10.10.72) 56(84) bytes of data.
^C
--- 10.10.10.72 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2055ms

root@openplotter:~# ifconfig wlan9
wlan9: error fetching interface information: Device not found
root@openplotter:~# ifconfig wlan9 up
wlan9: ERROR while getting interface flags: No such device
root@openplotter:~# ping -c 3 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_seq=1 ttl=64 time=5.31 ms
64 bytes from 192.168.0.1: icmp_seq=2 ttl=64 time=3.93 ms
64 bytes from 192.168.0.1: icmp_seq=3 ttl=64 time=7.35 ms

--- 192.168.0.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 3.925/5.529/7.354/1.408 ms
root@openplotter:~# ifconfig wlan0
wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
       inet 192.168.0.234  netmask 255.255.255.0  broadcast 192.168.0.255
       inet6 2a02:8070:4280:b620:dea6:32ff:fef6:2b71  prefixlen 64  scopeid 0x0<global>
       inet6 fe80::dea6:32ff:fef6:2b71  prefixlen 64  scopeid 0x20<link>
       ether dc:a6:32:f6:2b:71  txqueuelen 1000  (Ethernet)
       RX packets 16528  bytes 1502361 (1.4 MiB)
       RX errors 0  dropped 0  overruns 0  frame 0
       TX packets 9004  bytes 2029363 (1.9 MiB)
       TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

root@openplotter:~#

Using the internal WiFi adaptor for both connecting to network and create ap wasn't stable enough I found, usb/WiFi adaptor solved this.