UAP-AC-LITE serial mod – debricking

I tend to push things too far and lock me out from my Hardware from time to time.

This time i set some wrong interface settings on my new Access Point running LEDE/OpenWRT. Sadly there is no working failsave mode available to repair the network settings.

But that’s not a problem, the board is provided with a serial port.

First it’s necessary to remove the front plate which is held by 5 tabs.

This port has the pinout +3,3V – RxD – TxD – GND.I have soldered pins on it to have it easy accessible.

I use as a Serial Port on my Laptop a CP2102 UART Bridge.

root@laptop:/home/cave# dmesg | tail
[19840.798867] usbcore: registered new interface driver usbserial
[19840.798904] usbcore: registered new interface driver usbserial_generic
[19840.798932] usbserial: USB Serial support registered for generic
[19840.800388] usbcore: registered new interface driver cp210x
[19840.800404] usbserial: USB Serial support registered for cp210x
[19840.800447] cp210x 2-2:1.0: cp210x converter detected
[19840.912702] usb 2-2: reset full-speed USB device number 2 using xhci_hcd
[19841.050680] xhci_hcd 0000:03:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff88009ea91388
[19841.050690] xhci_hcd 0000:03:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff88009ea91340
[19841.053055] usb 2-2: cp210x converter now attached to ttyUSB0

In Linux minicom is the terminal emulation program to go. Settings are 115200 Baud, 8N1, no flow control.

The Boot Log from LEDE looks as following:

U-Boot unifi-v1.6.2.235-g1aad87ce (Jun 30 2015 - 21:30:38)

DRAM: 
sri
ath_ddr_initial_config(278): (ddr2 init)
ath_sys_frequency: cpu 775 ddr 650 ahb 258
Tap values = (0xf, 0xf, 0xf, 0xf)
128 MB
Top of RAM usable for U-Boot at: 88000000
Reserving 231k for U-Boot at: 87fc4000
Reserving 192k for malloc() at: 87f94000
Reserving 44 Bytes for Board Info at: 87f93fd4
Reserving 36 Bytes for Global Data at: 87f93fb0
Reserving 128k for boot params() at: 87f73fb0
Stack Pointer at: 87f73f98
Now running in RAM - U-Boot at: 87fc4000
Flash: 16 MB
In: serial
Out: serial
Err: serial
Net: ath_gmac_enet_initialize...
No valid address in Flash. Using fixed address
ath_gmac_enet_initialize: reset mask:c02200 
athr_mgmt_init ::done
Dragonfly ----> S17 PHY *
 ath_gmac_enet_initialize: is_s17()=0, is_ar8033()=1, phy id1=4d phy_id2=d074 
WAN AR8033 PHY init 
athrs_ar8033_reg_init: Done 111 
Max resets limit reached exiting...
athr_gmac_sgmii_setup SGMII done
: cfg1 0x80000000 cfg2 0x7114
eth0: 00:03:7f:09:0b:ad
eth0 up
eth0
Setting 0x181162c0 to 0x20402100
Board: Copyright Ubiquiti Networks Inc. 2014
Hit any key to stop autoboot: 0 
## Starting application at 0x80200020 ...
Board: Ubiquiti Networks AR956X board (e517-33.1150.0030.0040)
 0. Name = u-boot, offset = 0, start_addr=9f000000, size=393216,start_sector=0, end_sector=5 
 1. Name = u-boot-env, offset = 60000, start_addr=9f060000, size=65536,start_sector=6, end_sector=6 
 2. Name = kernel0, offset = 70000, start_addr=9f070000, size=7929856,start_sector=7, end_sector=127 
 3. Name = kernel1, offset = 800000, start_addr=9f800000, size=7929856,start_sector=128, end_sector=248 
 4. Name = bs, offset = f90000, start_addr=9ff90000, size=131072,start_sector=249, end_sector=250 
 5. Name = cfg, offset = fb0000, start_addr=9ffb0000, size=262144,start_sector=251, end_sector=254 
 6. Name = EEPROM, offset = ff0000, start_addr=9fff0000, size=65536,start_sector=255, end_sector=255 
get_mtd_params: name=bs
ubnt_flash_read: addr=8023b480, sa=9ff90000, sz=131072 
ubnt_bootsel_init: bootsel magic=a34de82b, bootsel = 1 
UBNT application initialized 
## Application terminated, rc = 0x0
## Starting application at 0x80200020 ...
keep cfg partition. 
## Application terminated, rc = 0x0
## Starting application at 0x80200020 ...
ubnt_uwrite: Nothing to flash, exiting 
## Application terminated, rc = 0x0
## Starting application at 0x80200020 ...
Number of boot partitions = 2 
get_mtd_params: name=bs
ubnt_flash_read: addr=8023b480, sa=9ff90000, sz=131072 
ubnt_get_bootsel: Boot partition selected = 1 
Loading Kernel Image @ 81000000, size = 7929856 
Verifying 'kernel1' parition:OK
## Application terminated, rc = 0x0
## Booting image at 9f800000 ...
 Image Name: MIPS LEDE Linux-4.4.92
 Created: 2017-10-17 17:46:20 UTC
 Image Type: MIPS Linux Kernel Image (lzma compressed)
 Data Size: 1258164 Bytes = 1.2 MB
 Load Address: 80060000
 Entry Point: 80060000
 Verifying Checksum at 0x9f800040 ...OK
 Uncompressing Kernel Image ... OK
No initrd
## Transferring control to Linux (at address 80060000) ...
## Giving linux memsize in bytes, 134217728

Starting kernel ...

[ 0.000000] Linux version 4.4.92 (buildbot@builds-02.infra.lede-project.org) (gcc version 5.4.0 (LEDE GCC 5.4.0 r3101-bce140e) ) #0 Tue Oct 17 14:59:45 2017
[ 0.000000] bootconsole [early0] enabled
[ 0.000000] CPU0 revision is: 00019750 (MIPS 74Kc)
[ 0.000000] SoC: Qualcomm Atheros QCA956X ver 1 rev 0
[ 0.000000] Determined physical RAM map:
[ 0.000000] memory: 08000000 @ 00000000 (usable)
[ 0.000000] Initrd not found or empty - disabling initrd
[ 0.000000] No valid device tree found, continuing without
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000000000000-0x0000000007ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x0000000007ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x0000000007ffffff]
[ 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] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 32512
[ 0.000000] Kernel command line: board=UBNT-UF-AC-LITE mtdparts=spi0.0:384k(u-boot)ro,64k(u-boot-env)ro,7744k(firmware),7744k(ubnt-airos)ro,128k(bs)ro,256k(cfg)ro,64k(EEPROM)ro console=ttyS0,11d
[ 0.000000] PID hash table entries: 512 (order: -1, 2048 bytes)
[ 0.000000] Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Writing ErrCtl register=00000000
[ 0.000000] Readback ErrCtl register=00000000
[ 0.000000] Memory: 125328K/131072K available (3076K kernel code, 160K rwdata, 412K rodata, 312K init, 205K bss, 5744K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS:51
[ 0.000000] Clocks: CPU:775.000MHz, DDR:650.000MHz, AHB:258.333MHz, Ref:25.000MHz
[ 0.000000] clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 4932285024 ns
[ 0.000006] sched_clock: 32 bits at 387MHz, resolution 2ns, wraps every 5541893118ns
[ 0.008207] Calibrating delay loop... 385.84 BogoMIPS (lpj=1929216)
[ 0.071016] pid_max: default: 32768 minimum: 301
[ 0.075981] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.082957] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.092341] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[ 0.102742] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.110072] NET: Registered protocol family 16
[ 0.115891] MIPS: machine is Ubiquiti UniFi-AC-LITE
[ 0.339426] registering PCI controller with io_map_base unset
[ 0.345661] Can't analyze schedule() prologue at 800670fc
[ 0.358984] PCI host bridge to bus 0000:00
[ 0.363307] pci_bus 0000:00: root bus resource [mem 0x12000000-0x13ffffff]
[ 0.370588] pci_bus 0000:00: root bus resource [io 0x0001]
[ 0.376452] pci_bus 0000:00: root bus resource [??? 0x00000000 flags 0x0]
[ 0.383608] pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
[ 0.392012] pci 0000:00:00.0: invalid calibration data
[ 0.397797] pci 0000:00:00.0: BAR 0: assigned [mem 0x12000000-0x121fffff 64bit]
[ 0.405512] pci 0000:00:00.0: BAR 6: assigned [mem 0x12200000-0x1220ffff pref]
[ 0.413156] pci 0000:00:00.0: using irq 40 for pin 1
[ 0.418979] clocksource: Switched to clocksource MIPS
[ 0.425232] NET: Registered protocol family 2
[ 0.430583] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.437935] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.444682] TCP: Hash tables configured (established 1024 bind 1024)
[ 0.451462] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.457625] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.464480] NET: Registered protocol family 1
[ 0.472711] Crashlog allocated RAM at address 0x3f00000
[ 0.490033] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.496181] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[ 0.508521] io scheduler noop registered
[ 0.512696] io scheduler deadline registered (default)
[ 0.518282] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[ 0.527170] console [ttyS0] disabled
[ 0.551022] serial8250.0: ttyS0 at MMIO 0x18020000 (irq = 11, base_baud = 1562500) is a 16550A
[ 0.560121] console [ttyS0] enabled
[ 0.560121] console [ttyS0] enabled
[ 0.567662] bootconsole [early0] disabled
[ 0.567662] bootconsole [early0] disabled
[ 0.580366] m25p80 spi0.0: mx25l12805d (16384 Kbytes)
[ 0.585606] 7 cmdlinepart partitions found on MTD device spi0.0
[ 0.591759] Creating 7 MTD partitions on "spi0.0":
[ 0.596707] 0x000000000000-0x000000060000 : "u-boot"
[ 0.603635] 0x000000060000-0x000000070000 : "u-boot-env"
[ 0.610446] 0x000000070000-0x000000800000 : "firmware"
[ 0.629799] 2 uimage-fw partitions found on MTD device firmware
[ 0.635927] 0x000000070000-0x0000001b0000 : "kernel"
[ 0.642182] 0x0000001b0000-0x000000800000 : "rootfs"
[ 0.648580] mtd: device 4 (rootfs) set to be root filesystem
[ 0.654512] 1 squashfs-split partitions found on MTD device rootfs
[ 0.660909] 0x000000420000-0x000000800000 : "rootfs_data"
[ 0.667848] 0x000000800000-0x000000f90000 : "ubnt-airos"
[ 0.674680] 0x000000f90000-0x000000fb0000 : "bs"
[ 0.680842] 0x000000fb0000-0x000000ff0000 : "cfg"
[ 0.686988] 0x000000ff0000-0x000001000000 : "EEPROM"
[ 0.699934] libphy: ag71xx_mdio: probed
[ 1.370523] ag71xx ag71xx.0: connected to PHY at ag71xx-mdio.0:04 [uid=004dd074, driver=Atheros 8031/8033 ethernet]
[ 1.381861] eth0: Atheros AG71xx at 0xb9000000, irq 4, mode:SGMII
[ 1.389623] NET: Registered protocol family 10
[ 1.396970] NET: Registered protocol family 17
[ 1.401669] bridge: automatic filtering via arp/ip/ip6tables has been deprecated. Update your scripts to load br_netfilter if you need this.
[ 1.414787] 8021q: 802.1Q VLAN Support v1.8
[ 1.425064] VFS: Mounted root (squashfs filesystem) readonly on device 31:4.
[ 1.434102] Freeing unused kernel memory: 312K
[ 2.242449] init: Console is alive
[ 2.246134] init: - watchdog -
[ 3.083296] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[ 3.104439] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[ 3.113279] init: - preinit -
[ 3.913129] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 3.935766] random: procd: uninitialized urandom read (4 bytes read, 6 bits of entropy available)
Press the [f] key and hit [enter] to enter failsafe mode
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
[ 6.521268] eth0: link up (100Mbps/Full duplex)
[ 6.525976] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 7.213159] jffs2: notice: (362) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[ 7.230901] mount_root: switching to jffs2 overlay
[ 7.243259] urandom-seed: Seeding with /etc/urandom.seed
[ 7.340310] eth0: link down
[ 7.352452] procd: - early -
[ 7.355510] procd: - watchdog -
[ 7.966201] procd: - watchdog -
[ 7.970066] procd: - ubus -
[ 8.067457] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.078176] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.088227] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.097567] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.107182] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.116514] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.125980] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.135784] random: ubusd: uninitialized urandom read (4 bytes read, 13 bits of entropy available)
[ 8.145437] procd: - init -
Please press Enter to activate this console.
[ 8.483520] kmodloader: loading kernel modules from /etc/modules.d/*
[ 8.506009] ip6_tables: (C) 2000-2006 Netfilter Core Team
[ 8.519402] Loading modules backported from Linux version wt-2017-01-31-0-ge882dff19e7f
[ 8.527672] Backport generated by backports.git backports-20160324-13-g24da7d3c
[ 8.587506] PCI: Enabling device 0000:00:00.0 (0000 -> 0002)
[ 8.593567] ath10k_pci 0000:00:00.0: pci irq legacy oper_irq_mode 1 irq_mode 0 reset_mode 0
[ 8.813379] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/pre-cal-pci-0000:00:00.0.bin failed with error -2
[ 8.824471] ath10k_pci 0000:00:00.0: Falling back to user helper
[ 9.019462] firmware ath10k!pre-cal-pci-0000:00:00.0.bin: firmware_loading_store: map pages failed
[ 9.220586] ath10k_pci 0000:00:00.0: qca988x hw2.0 target 0x4100016c chip_id 0x043222ff sub 0000:0000
[ 9.230152] ath10k_pci 0000:00:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 1
[ 9.243146] ath10k_pci 0000:00:00.0: firmware ver 10.2.4-1.0-00016 api 5 features no-p2p,raw-mode,mfp crc32 0c5668f8
[ 9.254134] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/board-2.bin failed with error -2
[ 9.264928] ath10k_pci 0000:00:00.0: Falling back to user helper
[ 9.343343] firmware ath10k!QCA988X!hw2.0!board-2.bin: firmware_loading_store: map pages failed
[ 9.364515] ath10k_pci 0000:00:00.0: board_file api 1 bmi_id N/A crc32 bebc7c08
[ 10.475587] ath10k_pci 0000:00:00.0: htt-ver 2.1 wmi-op 5 htt-op 2 cal file max-sta 128 raw 0 hwcrypto 1
[ 10.695182] ip_tables: (C) 2000-2006 Netfilter Core Team
[ 10.707106] nf_conntrack version 0.5.0 (1963 buckets, 7852 max)
[ 10.740206] xt_time: kernel timezone is -0000
[ 10.765475] PPP generic driver version 2.4.2
[ 10.818507] NET: Registered protocol family 24
[ 10.852803] ieee80211 phy1: Atheros AR9561 Rev:0 mem=0xb8100000, irq=47
[ 10.866164] kmodloader: done loading kernel modules from /etc/modules.d/*
[ 11.743364] random: jshn: uninitialized urandom read (4 bytes read, 19 bits of entropy available)
[ 15.375016] device eth0 entered promiscuous mode
[ 15.390029] IPv6: ADDRCONF(NETDEV_UP): br-lan: link is not ready
[ 17.281331] eth0: link up (100Mbps/Full duplex)
[ 17.418004] IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready
[ 17.459082] br-lan: port 1(eth0) entered forwarding state
[ 17.464711] br-lan: port 1(eth0) entered forwarding state
[ 17.499544] device wlan1 entered promiscuous mode
[ 19.458989] br-lan: port 1(eth0) entered forwarding state
[ 19.646999] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[ 19.660881] IPv6: ADDRCONF(NETDEV_CHANGE): br-lan: link becomes ready
[ 19.689299] device wlan0 entered promiscuous mode
[ 21.179912] IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
[ 21.186686] br-lan: port 2(wlan1) entered forwarding state
[ 21.192431] br-lan: port 2(wlan1) entered forwarding state
[ 23.189012] br-lan: port 2(wlan1) entered forwarding state
[ 39.059895] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 39.066638] br-lan: port 3(wlan0) entered forwarding state
[ 39.072394] br-lan: port 3(wlan0) entered forwarding state
[ 41.068994] br-lan: port 3(wlan0) entered forwarding state
[ 44.663058] random: nonblocking pool is initialized

BusyBox v1.25.1 () built-in shell (ash)

_________
 / /\ _ ___ ___ ___
 / LE / \ | | | __| \| __|
 / DE / \ | |__| _|| |) | _|
 /________/ LE \ |____|___|___/|___| lede-project.org
 \ \ DE /
 \ LE \ / -----------------------------------------------------------
 \ DE \ / Reboot (17.01.4, r3560-79f57e422d)
 \________\/ -----------------------------------------------------------

root@uap-ac-lite:/#

If you have access to the root user, you can reconfigure as much as you want and repair your settings.

If it’s better to do a factory reset, you can also boot into failsafe by pressing [ f ] when asked for it.

[ 3.935766] random: procd: uninitialized urandom read (4 bytes read, 6 bits of entropy available) 
Press the [f] key and hit [enter] to enter failsafe mode 
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level 
[ 6.521268] eth0: link up (100Mbps/Full duplex)

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