Hi,
I'm trying to add an usb port but without success, this is my first time with openwrt so please be patient.
Long story short two days ago my TL-WA730RE (I'm new so I can't post links, it's in the wiki) running stock firmware stopped working (boot loop). With tftp I was able to install openwrt 15.05.1 (openwrt-15.05.1-ar71xx-generic-tl-wa730rev1-squashfs-factory.bin) and I discovered there is an hardware problem with the onboard wifi (Data bus error, epc == 80e838a8, ra == 80e838a8).
Obviously why bother to go to the hardware store and get a new device if I can spend 2 days to add an usb wifi dongle to use instead of the onboard module? 
I didn't found instructions to mod this particular model but there are informations for the TL-WA701ND v1 (also in the wiki) that is almost identical.
With opkg I installed kmod-usb-ohci and kmod-usb-core and rebooted.
After a reboot I see those messages:
[ 12.850000] usbcore: registered new interface driver usbfs
[ 12.850000] usbcore: registered new interface driver hub
[ 12.860000] usbcore: registered new device driver usb
[ 12.890000] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
[ 12.900000] ohci-platform: OHCI generic platform driver
I proceeded to solder D+ and D- from the SoC (AR7240, pin 73 (D-) and 74 (D+) ) to a female usb port, i also soldered the usb ground and added an external power supply to provide the 5V (the ground of the external power supply is in common).
I checked twice with a multimeter to see if the solder joint was ok and I found as expected 0ohm from the D+ and D- of the usb port to the SoC pin.
I powered on and the board booted correctly but no matter what usb device I plugin it's not recognized.
I tested with two pulldown resistors between D+ and D- (are the values critical? I didn't have 15k at hand, I had to use 20k instead) but without success. The mod on the TL-WA701ND works without additional components.
Am I missing something software side?
Here is the full kernel log. Please don't mind the crash of the ath9k module, that's due to the hardware fault. I'll remove that module later with a custom firmware image.
[ 0.000000] Linux version 3.18.23 (buildbot@builder1) (gcc version 4.8.3 (OpenWrt/Linaro GCC 4.8-2014.04 r47269) ) #1 Sun Jan 31 18:39:35 CET 2016
[ 0.000000] MyLoader: sysp=ffee7ee7, boardp=ffffffff, parts=f2e072e0
[ 0.000000] bootconsole [early0] enabled
[ 0.000000] CPU0 revision is: 00019374 (MIPS 24Kc)
[ 0.000000] SoC: Atheros AR7240 rev 2
[ 0.000000] Determined physical RAM map:
[ 0.000000] memory: 02000000 @ 00000000 (usable)
[ 0.000000] Initrd not found or empty - disabling initrd
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x00000000-0x01ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x00000000-0x01ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x00000000-0x01ffffff]
[ 0.000000] On node 0 totalpages: 8192
[ 0.000000] free_area_init_node: node 0, pgdat 803762b0, node_mem_map 81000000
[ 0.000000] Normal zone: 64 pages used for memmap
[ 0.000000] Normal zone: 0 pages reserved
[ 0.000000] Normal zone: 8192 pages, LIFO batch:0
[ 0.000000] Primary instruction cache 64kB, VIPT, 4-way, linesize 32 bytes.
[ 0.000000] Primary data cache 32kB, 4-way, VIPT, cache aliases, linesize 32 bytes
[ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 8128
[ 0.000000] Kernel command line: board=TL-WA901ND console=ttyS0,115200 rootfstype=squashfs,jffs2 noinitrd
[ 0.000000] PID hash table entries: 128 (order: -3, 512 bytes)
[ 0.000000] Dentry cache hash table entries: 4096 (order: 2, 16384 bytes)
[ 0.000000] Inode-cache hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.000000] Writing ErrCtl register=00000000
[ 0.000000] Readback ErrCtl register=00000000
[ 0.000000] Memory: 28324K/32768K available (2586K kernel code, 128K rwdata, 540K rodata, 256K init, 193K bss, 4444K reserved)
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS:51
[ 0.000000] Clocks: CPU:350.000MHz, DDR:350.000MHz, AHB:175.000MHz, Ref:5.000MHz
[ 0.000000] Calibrating delay loop... 232.24 BogoMIPS (lpj=1161216)
[ 0.080000] pid_max: default: 32768 minimum: 301
[ 0.080000] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.090000] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.100000] NET: Registered protocol family 16
[ 0.100000] MIPS: machine is TP-LINK TL-WA901ND
[ 0.330000] registering PCI controller with io_map_base unset
[ 0.350000] PCI host bridge to bus 0000:00
[ 0.350000] pci_bus 0000:00: root bus resource [mem 0x10000000-0x13ffffff]
[ 0.360000] pci_bus 0000:00: root bus resource [io 0x0000]
[ 0.360000] pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
[ 0.370000] pci 0000:00:00.0: [168c:002b] type 00 class 0x028000
[ 0.370000] pci 0000:00:00.0: fixup device configuration
[ 0.370000] pci 0000:00:00.0: reg 0x10: [mem 0x00000000-0x0000ffff 64bit]
[ 0.370000] pci 0000:00:00.0: supports D1
[ 0.370000] pci 0000:00:00.0: PME# supported from D0 D1 D3hot
[ 0.370000] pci_bus 0000:00: busn_res: [bus 00-ff] end is updated to 00
[ 0.370000] pci 0000:00:00.0: BAR 0: assigned [mem 0x10000000-0x1000ffff 64bit]
[ 0.380000] pci 0000:00:00.0: using irq 40 for pin 1
[ 0.380000] Switched to clocksource MIPS
[ 0.390000] NET: Registered protocol family 2
[ 0.390000] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.390000] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.400000] TCP: Hash tables configured (established 1024 bind 1024)
[ 0.410000] TCP: reno registered
[ 0.410000] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.420000] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.420000] NET: Registered protocol family 1
[ 0.430000] PCI: CLS 0 bytes, default 32
[ 0.430000] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.450000] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.450000] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[ 0.460000] msgmni has been set to 55
[ 0.470000] io scheduler noop registered
[ 0.470000] io scheduler deadline registered (default)
[ 0.480000] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[ 0.490000] console [ttyS0] disabled
[ 0.510000] serial8250.0: ttyS0 at MMIO 0x18020000 (irq = 11, base_baud = 10937500) is a 16550A
[ 0.520000] console [ttyS0] enabled
[ 0.530000] bootconsole [early0] disabled
[ 0.540000] m25p80 spi0.0: found s25sl032p, expected m25p80
[ 0.540000] m25p80 spi0.0: s25sl032p (4096 Kbytes)
[ 0.550000] 5 tp-link partitions found on MTD device spi0.0
[ 0.550000] Creating 5 MTD partitions on "spi0.0":
[ 0.560000] 0x000000000000-0x000000020000 : "u-boot"
[ 0.570000] 0x000000020000-0x000000141600 : "kernel"
[ 0.570000] 0x000000141600-0x0000003f0000 : "rootfs"
[ 0.580000] mtd: device 2 (rootfs) set to be root filesystem
[ 0.580000] 1 squashfs-split partitions found on MTD device rootfs
[ 0.590000] 0x000000360000-0x0000003f0000 : "rootfs_data"
[ 0.600000] 0x0000003f0000-0x000000400000 : "art"
[ 0.600000] 0x000000020000-0x0000003f0000 : "firmware"
[ 0.650000] libphy: ag71xx_mdio: probed
[ 1.240000] ag71xx-mdio.0: Found an AR7240/AR9330 built-in switch
[ 1.280000] eth0: Atheros AG71xx at 0xba000000, irq 5, mode:GMII
[ 1.290000] TCP: cubic registered
[ 1.290000] NET: Registered protocol family 17
[ 1.290000] bridge: automatic filtering via arp/ip/ip6tables has been deprecated. Update your scripts to load br_netfilter if you need this.
[ 1.310000] Bridge firewalling registered
[ 1.310000] 8021q: 802.1Q VLAN Support v1.8
[ 1.330000] VFS: Mounted root (squashfs filesystem) readonly on device 31:2.
[ 1.340000] Freeing unused kernel memory: 256K (80390000 - 803d0000)
[ 2.880000] init: Console is alive
[ 2.880000] init: - watchdog -
[ 4.960000] init: - preinit -
[ 5.850000] random: procd urandom read with 9 bits of entropy available
[ 9.300000] jffs2: notice: (339) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[ 9.330000] mount_root: switching to jffs2 overlay
[ 9.400000] procd: - early -
[ 9.400000] procd: - watchdog -
[ 10.350000] procd: - ubus -
[ 11.370000] procd: - init -
[ 12.790000] NET: Registered protocol family 10
[ 12.850000] usbcore: registered new interface driver usbfs
[ 12.850000] usbcore: registered new interface driver hub
[ 12.860000] usbcore: registered new device driver usb
[ 12.870000] ip6_tables: (C) 2000-2006 Netfilter Core Team
[ 12.890000] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
[ 12.900000] ohci-platform: OHCI generic platform driver
[ 12.910000] Loading modules backported from Linux version master-2015-03-09-0-g141f155
[ 12.920000] Backport generated by backports.git backports-20150129-0-gdd4a670
[ 12.930000] ip_tables: (C) 2000-2006 Netfilter Core Team
[ 12.950000] nf_conntrack version 0.5.0 (446 buckets, 1784 max)
[ 13.010000] xt_time: kernel timezone is -0000
[ 13.050000] cfg80211: Calling CRDA to update world regulatory domain
[ 13.080000] cfg80211: World regulatory domain updated:
[ 13.080000] cfg80211: DFS Master region: unset
[ 13.090000] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp), (dfs_cac_time)
[ 13.100000] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
[ 13.100000] cfg80211: (2457000 KHz - 2482000 KHz @ 20000 KHz, 92000 KHz AUTO), (N/A, 2000 mBm), (N/A)
[ 13.110000] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (N/A, 2000 mBm), (N/A)
[ 13.120000] cfg80211: (5170000 KHz - 5250000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (N/A)
[ 13.130000] cfg80211: (5250000 KHz - 5330000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (0 s)
[ 13.140000] cfg80211: (5490000 KHz - 5730000 KHz @ 160000 KHz), (N/A, 2000 mBm), (0 s)
[ 13.150000] cfg80211: (5735000 KHz - 5835000 KHz @ 80000 KHz), (N/A, 2000 mBm), (N/A)
[ 13.160000] cfg80211: (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 0 mBm), (N/A)
[ 13.240000] PPP generic driver version 2.4.2
[ 13.250000] NET: Registered protocol family 24
[ 13.350000] usbcore: registered new interface driver rtl8192cu
[ 13.370000] PCI: Enabling device 0000:00:00.0 (0000 -> 0002)
[ 13.380000] ath: phy0: Enable LNA combining
[ 13.380000] ath: EEPROM regdomain: 0x0
[ 13.380000] ath: EEPROM indicates default country code should be used
[ 13.380000] ath: doing EEPROM country->regdmn map search
[ 13.380000] ath: country maps to regdmn code: 0x3a
[ 13.380000] ath: Country alpha2 being used: US
[ 13.380000] ath: Regpair used: 0x3a
[ 13.390000] Data bus error, epc == 80e838a8, ra == 80e838a8
[ 13.390000] Oops[#1]:
[ 13.390000] CPU: 0 PID: 545 Comm: kmodloader Not tainted 3.18.23 #1
[ 13.390000] task: 81b8c9b0 ti: 81b3c000 task.ti: 81b3c000
[ 13.390000] $ 0 : 00000000 00000000 deadc0de 80ee12c0
[ 13.390000] $ 4 : b0009860 00009860 00000001 00000000
[ 13.390000] $ 8 : 00000000 80064f18 00000002 00000008
[ 13.390000] $12 : 00000001 00000001 0000003f fffffffb
[ 13.390000] $16 : 818d2010 00000003 00009860 00002710
[ 13.390000] $20 : 00000001 00000000 818d2306 00000000
[ 13.390000] $24 : 00000008 80ee1450
[ 13.390000] $28 : 81b3c000 81b3d9a8 00000003 80e838a8
[ 13.390000] Hi : 00000001
[ 13.390000] Lo : 398f4000
[ 13.390000] epc : 80e838a8 ath9k_hw_wait+0x64/0xb0 [ath9k_hw]
[ 13.390000] Not tainted
[ 13.390000] ra : 80e838a8 ath9k_hw_wait+0x64/0xb0 [ath9k_hw]
[ 13.390000] Status: 1000e403 KERNEL EXL IE
[ 13.390000] Cause : 1080001c
[ 13.390000] PrId : 00019374 (MIPS 24Kc)
[ 13.390000] Modules linked in: ath9k(+) rtl8192cu ath9k_common rtl_usb rtl8192c_common pppoe ppp_async iptable_nat ath9k_hw ath rtlwifi pppox ppp_generic nf_nat_ipv4 nf_conntrack_ipv6 nf_conntrack_ipv4 mac80211 ipt_REJECT ipt_MASQUERADE cfg80211 xt_time xt_tcpudp xt_state xt_nat xt_multiport xt_mark xt_mac xt_limit xt_id xt_conntrack xt_comment xt_TCPMSS xt_REDIRECT xt_LOG xt_CT slhc nf_reject_ipv4 nf_nat_masquerade_ipv4 nf_nat_ftp nf_nat nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_rtcache nf_conntrack_ftp nf_conntrack iptable_raw iptable_mangle iptable_filter ip_tables crc_ccitt compat ohci_platform ohci_hcd ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 nf_log_common ip6table_raw ip6table_mangle ip6table_filter ip6_tables x_tables usbcore nls_base usb_common ipv6 arc4 crypto_blkcipher gpio_button_hotplug
[ 13.390000] Process kmodloader (pid: 545, threadinfo=81b3c000, task=81b8c9b0, tls=7715d440)
[ 13.390000] Stack : 00000000 00000000 00000000 00000000 00000000 818d2010 00009860 00009860
[ 13.390000] 00023f60 81800964 00000001 80e8f2c8 00000001 818d2300 08000000 80e920f8
[ 13.390000] 000186a0 818d2010 00000001 818d2010 818d2300 00000000 00023f60 80e8f4c0
[ 13.390000] 00000008 80e84f1c 818d33ac 80e9c9e4 00000000 00000000 818d2010 818d2300
[ 13.390000] 00000000 00023f60 81800964 00000001 00000001 00000000 00000003 80e87278
[ 13.390000] ...
[ 13.390000] Call Trace:
[ 13.390000] [<80e838a8>] ath9k_hw_wait+0x64/0xb0 [ath9k_hw]
[ 13.390000] [<80e8f2c8>] ar5008_hw_attach_phy_ops+0x17e8/0x1e6c [ath9k_hw]
[ 13.390000]
[ 13.390000]
[ 13.390000] Code: 02402821 0060f809 00000000 <00541024> 10550008 24020001 0c067c50 2404000a 083a0e24
[ 13.630000] ---[ end trace 50dd3357cf3b0823 ]---
[ 25.130000] device eth0 entered promiscuous mode
[ 25.160000] IPv6: ADDRCONF(NETDEV_UP): br-lan: link is not ready
[ 61.740000] random: nonblocking pool is initialized(Last edited by just.an.user on 12 Jul 2017, 20:54)