Everything you Ever Wanted to know about Serial - TTL

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Murrkf
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PostPosted: Wed Aug 19, 2009 3:11    Post subject: Reply with quote
Don't have a router connected yet. Will likely have to wait until one of my test units arrive.....or I'll be a dead man.

IF everything is connected properly....what irreparable harm will I be capable of?

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PostPosted: Wed Aug 19, 2009 3:47    Post subject: Reply with quote
Murrkf wrote:
IF everything is connected properly....what irreparable harm will I be capable of?


It's all good.. Don't be scared Razz ... If everything is shorted properly, you can do no harm till you power up.

If you are conected properly, you can do no harm, unless you have everything shorted properly and then power up.

JK.. It'll be fine. My advantage is: I fix routers for free... If I f$ck it up, I'm not scared because..

A). Not my router

B). I didn't brick it in the 1st place

C). I can return it in the same box just as bricked as when I got it

D). Never failed (yet)

BTW... See my pics? That is a V8.. Notice the flashchip? It is not an Eon.. It is a samsung.. How did that happen Wink

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fggs
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PostPosted: Wed Aug 19, 2009 3:49    Post subject: Reply with quote
If everything is connected properly I don't see how can you cause irreparable harm, but if you connect something wrong you can fry your max3232 and lose your adapter.
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PostPosted: Wed Aug 19, 2009 4:02    Post subject: Reply with quote
fggs wrote:
but if you connect something wrong you can fry your max3232 and lose your adapter.


That's the spirit Razz

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barryware
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PostPosted: Wed Aug 19, 2009 4:11    Post subject: Reply with quote
Murrkf... Really, don't worry.. I'm having fun...

When I was trying to figure out why the console wasn't working on a V8 when I was assured by a dev that the v8 does have a working console, when I was switching wires, the worst thing that happened was the router re-booted.

Of course, these were temporary (touch & watch for sparks) connections... When the leds went off and the router rebooted, I figured that I had something not connected right Shocked

Don't be scared... And don't experiment with an expensive router. Wink

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Murrkf
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PostPosted: Wed Aug 19, 2009 4:14    Post subject: Reply with quote
KeithB wrote:
I was gonna mention it, and BW's pictures show it clearly: old 3.5" floppy drive power cables fit very well on those 4-pin connectors. Smile


Yup. This worked well. I now have a usb to serial adapter, connected to my device, with a 3.5 floppy drive power cable clipped in to those four connections. Now I need to get some ends, and based on the fact that they aren't standard, I think I need some alligator clips.

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Murrkf
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PostPosted: Wed Aug 19, 2009 17:48    Post subject: Reply with quote
Do any routers come with serial headers installed? What do people use for serial headers?
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DHC_DarkShadow
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PostPosted: Wed Aug 19, 2009 17:59    Post subject: Reply with quote
Murrkf wrote:
Do any routers come with serial headers installed? What do people use for serial headers?


Header pins similar to the JTAG header. Some dual row some single row. They have to be soldered in. And it all really depends on were the proper pinouts are for serial. All the ones on my linky's have bare wholes for the pins to be soldered in.

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Murrkf
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PostPosted: Wed Aug 19, 2009 19:29    Post subject: Reply with quote
This is a wonderful post by Redhawk in Pock's post about debricking a WL500W by serial:

redhawk0 wrote:
Serial cable is required to possibly debrick units without JTAG port.

Serial cable can be either USB or DB9 connection type.
It must be capable of doing voltage level shift to +3.3V not just +5V.

There are 4 connections that are required for Serial to function properly. +3.3V, GND, Tx and Rx.

Some boards are NOT marked with pin designation. You must ohm out your power and GND in this case so things don't get connected backwards and blow out your cable chip. Then you can guess at the last 2 Rx and Tx lines.

The cable has Rx and Tx but these are relative to the cable...so Rx line needs to be connected to the routers Tx line....because the router's designator's are relative to the router.

So Tx and Rx get crossed for proper connection.

On routers that have 2 Serial ports (Tx0, Tx1 and Rx0, Rx1) you generally use the zero port for your connections (I've not seen a router yet that you connect up to the "one" side)

Once you make the connection setup your computer Serial terminal display for 115200 8-N-1. Plug in your router and you should see text on the screen. You can monitor the tty output of the CFE as it is booting...or break in using Cntl-C and enter low level commands to try to fix things.

The most useful for our purpose is the

"nvram show" and "nvram erase" commands.

Once the nvram is erased...type "reboot" or power cycle it....now tftp your firmware....or just let it boot up if firmware was previously loaded properly.

So...that's it in a nutshell....any questions/comments....just ask.

But before someone asks....NO you can NOT reload a CFE if it is damaged through the Serial port...a working CFE has to be running in order to get CFE commands....so loading a CFE without a CFE is impossible.

redhawk

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DHC_DarkShadow
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PostPosted: Wed Aug 19, 2009 19:39    Post subject: Reply with quote
Murrkf wrote:
This is a wonderful post by Redhawk in Pock's post about debricking a WL500W by serial:

redhawk0 wrote:
On routers that have 2 Serial ports (Tx0, Tx1 and Rx0, Rx1) you generally use the zero port for your connections (I've not seen a router yet that you connect up to the "one" side)

redhawk


I think the routers with 2 serials, the"one"side is for hooking up serial controlled devices, I may be wrong. I seen somewhere someone put 2 serial ports on 54g. I'll hunt for where I saw that when i get home.

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barryware
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PostPosted: Wed Aug 19, 2009 19:52    Post subject: Reply with quote
DHC_DarkShadow wrote:
Murrkf wrote:
This is a wonderful post by Redhawk in Pock's post about debricking a WL500W by serial:

redhawk0 wrote:
On routers that have 2 Serial ports (Tx0, Tx1 and Rx0, Rx1) you generally use the zero port for your connections (I've not seen a router yet that you connect up to the "one" side)

redhawk


I think the routers with 2 serials, the"one"side is for hooking up serial controlled devices, I may be wrong. I seen somewhere someone put 2 serial ports on 54g. I'll hunt for where I saw that when i get home.


I think what red meant was the data output when the router boots as well as accessing the cfe is always on the zero side.

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Murrkf
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PostPosted: Wed Aug 19, 2009 20:42    Post subject: Reply with quote
Okay...I cracked my Asus wl520gu. Man..you sure don't want to brick one of these....absolutely no jtag port. But the J4 is a serial port... I decide to check out the terminals.
1
2
3
4


So I put my lead to #1...the square one, and check for voltage with 2, not much. With 3, .10..about the same. So I hook it to 4 and see 3.3. AH. I think. Those are vvc and ground. But then I find that if I put my negative to #4, I get 3.3 from 1, 2 AND 3.

Pretty hard to figure out pos and negative if all have voltage!

Posting a picture of the four screws on the bottom to take this apart...two exposed, two under the feet.



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LOM: "If you show that you have not bothered to read the forum announcements or to follow the advices in them then the level of help available for you will drop substantially, also known as Murrkf's law.."
barryware
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PostPosted: Wed Aug 19, 2009 21:18    Post subject: Reply with quote
Pin 1 is usually vcc.. to check, volt meter positive lead to pin 1, negitive lead to a different ground spot. Say the metal shield on the switch port.

Now with no power, use an ohm meter from pin 4 to a ground point. You should have zero ohms if pin four is indeed ground.

So once you get vcc and ground figured out, the other two are tx & rx.. you got a 50/50 chance of hitting it right 1st time.

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Murrkf
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PostPosted: Wed Aug 19, 2009 21:23    Post subject: Reply with quote
I've been told that "Google is my friend". (Well, at least that's ONE that I have)

http://mightyohm.com/blog/2008/10/building-a-wifi-radio-part-3-hacking-the-asus-wl-520gu/

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LOM: "If you show that you have not bothered to read the forum announcements or to follow the advices in them then the level of help available for you will drop substantially, also known as Murrkf's law.."
barryware
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PostPosted: Wed Aug 19, 2009 21:27    Post subject: Reply with quote
you got it right..

If you mix up tx & rx it can't hurt anything.. You just won't get any output.

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