Did wifi configuration change between 3.8 and 4.08? Need help

I have had wireless working on a 3.8 BBB for quite some time and I wanted to move to a v4 kernel in the hope that the “lagginess” of the wifi connection would be reduced. I loaded another board with the LTS RT v4 kernel, did apt-get install wireless-tools wireless-regdb crda, and put my ssid and passphrase in /etc/network/interfaces. The results are:

root@beaglebone:~# ifup -vv wlan0

Configuring interface wlan0=wlan0 (inet)

run-parts --exit-on-error --verbose /etc/network/if-pre-up.d

run-parts: executing /etc/network/if-pre-up.d/wireless-tools

dhclient -v -pf /run/dhclient.wlan0.pid -lf /var/lib/dhcp/dhclient.wlan0.leases wlan0

Internet Systems Consortium DHCP Client 4.3.1

Copyright 2004-2014 Internet Systems Consortium.

All rights reserved.

For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/wlan0/c4:6e:1f:10:0e:70

Sending on LPF/wlan0/c4:6e:1f:10:0e:70

Sending on Socket/fallback

DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 5

DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 7

DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 16

DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 9

DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 19

DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 5

No DHCPOFFERS received.

No working leases in persistent database - sleeping.

I must have missed something. I even copied the interfaces file over from the 3.8 machine, but no joy. Of course, I also went from Wheezy to Jessie.

The hardware is a TP-Link WN722N (Atheros) that I haven’t had any problems with - in fact it does an “iwlist wlan0 scan” just fine in the new machine. This seems to a software problem.

It is interesting that even after installing crda and wireless-regdb, dmesg shows:

[ 10.512066] ath: EEPROM indicates we should expect a country code

[ 10.512073] ath: doing EEPROM country->regdmn map search

[ 10.512079] ath: country maps to regdmn code: 0x52

[ 10.512085] ath: Country alpha2 being used: CN

[ 10.512090] ath: Regpair used: 0x52

[ 10.552110] ieee80211 phy0: Atheros AR9271 Rev:1

[ 10.638305] cfg80211: Regulatory domain changed to country: CN

To be complete, ifconfig shows:

wlan0 Link encap:Ethernet HWaddr c4:6e:1f:10:0e:70

UP BROADCAST MULTICAST MTU:1500 Metric:1

RX packets:0 errors:0 dropped:0 overruns:0 frame:0

TX packets:0 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

and iwconfig wlan0 shows:

wlan0 IEEE 802.11bgn ESSID:off/any

Mode:Managed Access Point: Not-Associated Tx-Power=20 dBm

Retry short limit:7 RTS thr:off Fragment thr:off

Encryption key:off

Power Management:off

and this is the interfaces file:

auto wlan0

iface wlan0 inet dhcp

wpa-ssid “my_ssid”

wpa-psk “my_passphrase”

I would appreciate any help that you can provide,
Tim