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Topic: Debrick - TP-LINK WR841ND 7.2 via serial console - only garbage

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Hi,
one of my router TP-LINK WR841ND 7.2 do not boot after remote firmware upgrade (OpenWRT trunk) - it react to connected LAN port, but I'm not able to enter failsafe, so I'm trying serial console for the 1st time. The system LED is even all the time off - never blink or similar. Following http://wiki.openwrt.org/toh/tp-link/tl- … l.console.

The problem which I have, I'm trying to get it boot via console, but I'm just seeing garbage (somehow I see it's probably booting). I have tried to add also 10kOhm (actually 10.11 kOhm, not sure whether this is a problem) between TX and VCC
Is it due to the used DELOCK USB-RS232 (61018) ? Seeing that everyone is using Nokia DKU-5 TTL or CA-42...

Thank you for your help.

Putty
Garbage

(Last edited by sharkys on 10 Mar 2015, 20:42)

you cannot use an RS232 adapter, it uses +/- 12V and can easilly fry your board.

use only TTL (3.3v) adapters.

never connect the VCC pin to anything wink

So if I got you correctly, the only solution is to get  Nokia DKU-5 TTL or CA-42 ?

VCC - I have never connected it to anything yet.

Any USB to serial adapter with a 3.3 volt "TTL" interface will work.  Or you can build a circuit to convert from RS-232 to TTL, but that is unnecessarily complicated compared to just getting TTL from the adapter to begin with.

try other speeds as:  75, 110, 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200 bit/s
http://en.wikipedia.org/wiki/Serial_port
also ttl-serial(3.3v) 8N1 no flow control

(Last edited by makarel on 11 Mar 2015, 15:46)

OK, thank you for all your comments, so it was finally successful with Nokia DKU-5 TTL . But now I have got another problem. Following the guide on https://forum.openwrt.org/viewtopic.php?id=33906, I uploaded the firmware, everything is fine, router boot first - but the second reboot get stuck always and I can again bring it to life only via serial and only first boot is fine.

Anyone get any idea what is wrong please ?

U-Boot 1.1.4 (Sep  3 2010 - 12:35:51)

AP99 (ar7241 - Virian) U-boot
DRAM:
sri
ar7240_ddr_initial_config(133): virian ddr1 init
#### TAP VALUE 1 = 0xf, 2 = 0x10 [0x0: 0x1f]
32 MB
id read 0x100000ff
sector count = 64
Flash:  4 MB
Using default environment

In:    serial
Out:   serial
Err:   serial
Net:   ag7240_enet_initialize...
No valid address in Flash. Using fixed address
No valid address in Flash. Using fixed address
Virian MDC CFG Value ==> 4
: cfg1 0xf cfg2 0x7014
eth0: 00:03:7f:09:0b:ad
eth0 up
Virian MDC CFG Value ==> 4
: cfg1 0xf cfg2 0x7214
eth1: 00:03:7f:09:0b:ad
ATHRS26: resetting s26
ATHRS26: s26 reset done
eth1 up
eth0, eth1
Autobooting in 1 seconds
## Booting image at 9f020000 ...
   Uncompressing Kernel Image ... OK

Starting kernel ...
[    0.000000] Linux version 3.18.8 (someone@debian) (gcc version 4.8.3 (OpenWrt/Linaro GCC 4.8-2014.04 r44597) ) #3 Thu Mar 5 13:21:11 CST 2015
[    0.000000] bootconsole [early0] enabled
[    0.000000] CPU0 revision is: 00019374 (MIPS 24Kc)
[    0.000000] SoC: Atheros AR7241 rev 1
[    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] 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: 8128
[    0.000000] Kernel command line:  board=TL-WR841N-v7 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: 28456K/32768K available (2480K kernel code, 120K rwdata, 528K rodata, 252K init, 188K bss, 4312K reserved)
[    0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[    0.000000] NR_IRQS:51
[    0.000000] Clocks: CPU:400.000MHz, DDR:400.000MHz, AHB:200.000MHz, Ref:5.000MHz
[    0.000000] Calibrating delay loop... 265.42 BogoMIPS (lpj=1327104)
[    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-WR841N/ND v7
[    0.550000] registering PCI controller with io_map_base unset
[    0.560000] PCI host bridge to bus 0000:00
[    0.570000] pci_bus 0000:00: root bus resource [mem 0x10000000-0x13ffffff]
[    0.570000] pci_bus 0000:00: root bus resource [io  0x0000]
[    0.580000] pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
[    0.580000] pci 0000:00:00.0: fixup device configuration
[    0.590000] pci 0000:00:00.0: BAR 0: assigned [mem 0x10000000-0x1000ffff 64bit]
[    0.590000] pci 0000:00:00.0: using irq 40 for pin 1
[    0.600000] Switched to clocksource MIPS
[    0.600000] NET: Registered protocol family 2
[    0.610000] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[    0.610000] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[    0.620000] TCP: Hash tables configured (established 1024 bind 1024)
[    0.630000] TCP: reno registered
[    0.630000] UDP hash table entries: 256 (order: 0, 4096 bytes)
[    0.640000] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[    0.640000] NET: Registered protocol family 1
[    0.650000] futex hash table entries: 256 (order: -1, 3072 bytes)
[    0.660000] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[    0.670000] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[    0.680000] msgmni has been set to 55
[    0.700000] io scheduler noop registered
[    0.700000] io scheduler deadline registered (default)
[    0.710000] Serial: 8250/16550 driver, 1 ports, IRQ sharing disabled
[    0.710000] console [ttyS0] disabled

(Last edited by sharkys on 13 Mar 2015, 20:29)

OK, so I replaced my own compiled firmware (OpenWrt Chaos Calmer r44597 ) with the latest trunk one... http://downloads.openwrt.org/snapshots/ … actory.bin

What I don't get, I'm using currently the same version (r44597) on several other routers - TP-Link TL-WR841N/ND v8, TP-Link TL-WA850RE v1, TP-Link TL-WR841N/ND v8,TP-Link TL-WR842N/ND v1 but only on TL-WR841ND v7 it's not booting ?

I don't get it, all of them got the same size, I'm building it using "env switch"... is it possible that just r44597  got broken for TL-WR841ND v7 ?

(Last edited by sharkys on 13 Mar 2015, 20:53)

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