Asus RT-N12 serial mod

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NiHaoMike
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Joined: 29 Dec 2010
Posts: 17
Location: Texas

PostPosted: Wed Dec 29, 2010 6:24    Post subject: Asus RT-N12 serial mod Reply with quote
Recently, I got a new Asus RT-N12. As an electrical engineer, I like to modify electronic devices for fun.

For a little background info, I started playing with electronic kits when I was in first grade, started working with OpenWRT in 11th grade, and I'm currently a senior at Texas A&M University. Therefore, I'm very familiar with how to design and modify circuits.

On the routers I have worked on before, I installed a serial console port since it is extremely useful for debugging. On the previous ones I have worked on (two F5D7230-4s and a WRT54G), there was more than enough room on the back for a proper serial console port. But not on the RT-N12. And the case was just too beautiful for me to just cut a hole for the port elsewhere.

After a little thinking, I realized that only 4 wires are used in a standard 10/100 Ethernet port. That leaves 4 wires that I can use for a serial interface. Therefore, I can add a serial port to one of the Ethernet ports without losing any functions. I found an adapter to convert the 9 pin serial connector to RJ-45, originally intended for the console port on Cisco equipment. The pinout would interfere with the Ethernet pinout, so I made an adapter to solve that problem.

Here it is:

That's how to have your cake and eat it too. It would work on any router without Gigabit. (And yes, there are a few other "toys" I work with in that picture. I'm on winter break and the temporary "lab" I set up at home is a little crowded.)

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I want my router to perform well and look attractive. My best friend Tiffany Yep is a model and a digital communications engineer. Inspiration from nature?
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NiHaoMike
DD-WRT Novice


Joined: 29 Dec 2010
Posts: 17
Location: Texas

PostPosted: Wed Dec 29, 2010 17:57    Post subject: Reply with quote
I just finished drawing the schematic:

Note that TX, RX, and DTR on the RJ-45 is from the device perspective. They would be wired to RX, TX, and DSR/CD on the serial port. Serial settings are the common 115,200bps 8N1.

I just wired it up freehand. After testing to make sure it works, I covered it in sealant to protect it from vibrations.

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I want my router to perform well and look attractive. My best friend Tiffany Yep is a model and a digital communications engineer. Inspiration from nature?
sturesur
DD-WRT Novice


Joined: 07 Aug 2010
Posts: 17

PostPosted: Thu Dec 30, 2010 19:05    Post subject: Only in Texas! Reply with quote
Hey - this is a simple but ingenious solution!

Thanks for sharing!!!!




Joined: 01 Jan 1970
Posts:

PostPosted: Thu Jan 06, 2011 6:53    Post subject: pinout? Reply with quote
Great work! I'm curious about the pinout. How does the N12 serial header compare to the pinout of the 520ug? My RT-N12 seems to have gnd on the left and 3.3 on the far right. Whats the pin J1? is that Tx? I connected a ftdi 3v3 and couldn't get the serial port to come up. It did cause the router to repeatedly reboot and wipe the flash. Maybe one of those pins is reset? Maybe I just got it too hot when I desoldered it.
NiHaoMike
DD-WRT Novice


Joined: 29 Dec 2010
Posts: 17
Location: Texas

PostPosted: Fri Jan 07, 2011 4:24    Post subject: Re: pinout? Reply with quote
onlyme wrote:
Great work! I'm curious about the pinout. How does the N12 serial header compare to the pinout of the 520ug? My RT-N12 seems to have gnd on the left and 3.3 on the far right. Whats the pin J1? is that Tx? I connected a ftdi 3v3 and couldn't get the serial port to come up. It did cause the router to repeatedly reboot and wipe the flash. Maybe one of those pins is reset? Maybe I just got it too hot when I desoldered it.

On mine, looking at the top of the board with the front facing you, it's GND, TX, RX, and 3.3v from left to right on header J1.

_________________
I want my router to perform well and look attractive. My best friend Tiffany Yep is a model and a digital communications engineer. Inspiration from nature?




Joined: 01 Jan 1970
Posts:

PostPosted: Wed Jan 12, 2011 17:03    Post subject: pinout Reply with quote
I soldered male header pins on another N12. I guess I didn't overheat it this time b/c it worked! Thanks.
donphillipe
DD-WRT User


Joined: 18 Jun 2008
Posts: 79

PostPosted: Tue Nov 01, 2011 3:44    Post subject: Great work Reply with quote
Any plans for a USB addition?
shayanafz
DD-WRT Novice


Joined: 12 Sep 2013
Posts: 1

PostPosted: Thu Sep 12, 2013 13:30    Post subject: Re: Only in Texas! Reply with quote
Hi
can you help me?I want make a device for converting ethernet to rs485.may I do that?
thank's a lot.
Shayan
shayanafz@yahoo.com
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