Author Topic: Possible to connect Arduino to TTL serial?  (Read 11301 times)

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Offline Stonent

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Possible to connect Arduino to TTL serial?
« on: August 12, 2013, 07:50:05 am »
I'm having trouble googling what I'm looking for, and this may not exist or I may be just completely stupid.

What I'd like to know is if there are any libs or examples of using an Arduino Uno to connect to a TTL serial connector on a board.

Basically avoiding buying an FTDI cable or building something with a MAX232 to level shift the port.

I've got an old no-name Airlink AR315W wireless router from 7 or 8 years ago that I bricked that I just found in storage and I thought hey I know a bit more about electronics now, maybe I could revive this thing. I remember it used to lock up all the time so I found the OEM of the board inside and attempted to load their firmware on it and killed it.  Turns out these things had overheat problems because the 12V psu generated too much heat internally and they would send you a lower powered supply if you had the issues. Too bad I took matters into my own hands and voided the warranty (before I knew about the power issue)

I've got two connections on this board, an unpopulated 2x10 header and an unpopulated 4 pin header near the main chip. From this I'm guessing an ARM JTAG port and a TTL serial port. I want to probe the unpopulated 4 pin header and see if there are any signs of life visible.

Sadly I had an FTDI cable about 10 years ago. It allowed me to use a Motorola "TDMA" phone as a 9.6Kbps internet connection. I think it got thrown out with the phone a long time ago. I remember specifically loading the FTDI driver and grumbling about how it didn't just recognize as a standard serial port.

As far as internal power regulation there's a DC to DC converter that drops the voltage from +12 to +5, and next to it a regulator that turns +5 into +3.3, and two more regulators in other places that turn 3.3 into 2.5.  It really seems silly to do all that power shifting and having two identical regulators in different locations seems odd as well.

So back to the main issue, I'd like to probe the 4 pin header to see if it is a TTL serial port maybe using an Arduino if possible.
« Last Edit: August 16, 2013, 01:47:23 am by Stonent »
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Offline Stonent

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Re: Possible to connect Arduino to TTL serial?
« Reply #1 on: August 12, 2013, 07:52:55 am »
I guess googling "arduino as ttl level converter" was what I needed to do... What do you think?

http://forum.arduino.cc/index.php/topic,18243.0.html

Sound promising?
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Offline westfw

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Re: Possible to connect Arduino to TTL serial?
« Reply #2 on: August 12, 2013, 07:41:47 pm »
Are you trying to get the arduino to talk to your router, or are you trying to get your desktop to talk to the router using the arduino as a replacement for an FTDI cable?   The link you referenced talks about the latter.
 

Offline Stonent

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Re: Possible to connect Arduino to TTL serial?
« Reply #3 on: August 12, 2013, 10:13:49 pm »
Are you trying to get the arduino to talk to your router, or are you trying to get your desktop to talk to the router using the arduino as a replacement for an FTDI cable?   The link you referenced talks about the latter.

Open a serial console on the PC and talk to the router.
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Offline olsenn

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Re: Possible to connect Arduino to TTL serial?
« Reply #4 on: August 12, 2013, 10:26:53 pm »
The Arduino will work with TTL protocols, yes; however, don't try to connect it to an RS232 port! Those devices require +-12V instead of 0v-5v (TTL)
 

Offline westfw

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Re: Possible to connect Arduino to TTL serial?
« Reply #5 on: August 13, 2013, 12:31:39 am »
The port on your router is likely to be "logic level" rather than "rs232 level."
However, it's also likely to have logic levels lower than the 5V "TTL" levels the Arduino will generate, so it may not be usable...
 

Offline Stonent

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Re: Possible to connect Arduino to TTL serial?
« Reply #6 on: August 13, 2013, 01:02:41 am »
The Arduino will work with TTL protocols, yes; however, don't try to connect it to an RS232 port! Those devices require +-12V instead of 0v-5v (TTL)

Yes I know that, that's why I was doing it this way.
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Offline MrAureliusR

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Re: Possible to connect Arduino to TTL serial?
« Reply #7 on: August 15, 2013, 04:08:54 pm »
Why's it such a problem to use a MAX232? You can get lots of 10 for like $5 on eBay, 5 1.0uF caps later and bang it works like a charm. Simple, easy solution. Other options are way too complex and there's no point -- just take a bit of vero or protoboard, solder on the MAX232 and the caps, feed it 5V and attach the Tx and Rx pins to the respective inputs and outputs, and you can keep this little module around whenever you need to connect TTL to Serial. They come in handy a LOT, trust me.


Here's an annotated photo of one of the ones I've got laying around:



Which is based off of the example circuit from the MAX232 datasheet:



[EDIT] After reading the link you posted, I think I understand better. The problem is, it looks like they were using the Arduino to talk to the hard drive, and then using USB or something different to communicate from the Arduino to the PC... I'm guessing anyway. THAT is perhaps viable, I don't know anything about Arduino's really. Okay, after reading it AGAIN I realize that they were using serial directly. I suppose this is because the hard drive in question created voltage levels high enough, and the arduino just passed them straight through? I'm guessing this means that the serial port on their computer was sensitive enough to pick up the signals, which I wouldn't rely on. The MAX232 or the ST equivalent (ST232 something something) still seems the most reliable way to do this...
« Last Edit: August 15, 2013, 04:26:09 pm by MrAureliusR »
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Offline Crazy Ape

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Re: Possible to connect Arduino to TTL serial?
« Reply #8 on: August 15, 2013, 04:55:34 pm »
This circuit will work fine if you don't have an RS232 level converter. Power it with VCC from the device you're talking to. I've tested this on 3.3v and 5v TTL devices.
http://picprojects.org.uk/projects/simpleSIO/ssio.htm
 

Offline Monkeh

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Re: Possible to connect Arduino to TTL serial?
« Reply #9 on: August 15, 2013, 05:14:10 pm »
You have an Arduino.. it has a TTL serial converter on it already. Unplug the chip and connect the lines to the router..
 

Offline Stonent

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Re: Possible to connect Arduino to TTL serial?
« Reply #10 on: August 16, 2013, 12:42:01 am »
You have an Arduino.. it has a TTL serial converter on it already. Unplug the chip and connect the lines to the router..

Yeah basically what I did. But I got no data on what I thought was the serial lines.

Back to the drawing board.
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Offline fluxcapacitor

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Re: Possible to connect Arduino to TTL serial?
« Reply #11 on: August 16, 2013, 01:12:52 am »
Hi,the AR3135W has a few clones.I had/have a buffalo WYR-G54 clone that died a few years ago, it was the caacitors that needed replacing.I also updated the firmware by following the steps given in a few forums :
 http://www.eutony.net/2009/06/17/buffalo-wyr-g54-firmware/
http://www.dslreports.com/forum/r10883070-Airlink-AR315W-having-some-fun

I settled on the sercomm firmware as it was the most stable,and added wpa (tkip) .You`ll need the sercom tool to upgrade.
http://www.nslu2-linux.org/wiki/Main/SercommFirmwareUpdater

 

Offline Stonent

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Re: Possible to connect Arduino to TTL serial?
« Reply #12 on: August 16, 2013, 01:44:55 am »
Yeah I got it to come up finally by holding down the reset button for a long period of time and then it cycled through a few light patterns.

It says Firmware rev FF.FF in the web console, and seems to be read only, but DHCP works on the 4 ports.

The only firmware that Airlink has on their site are from version X to Z and version Y to Z.

I tried both of those and they both failed the CRC check so I need a way to put a complete firmware on this thing without failing a CRC check.  Trying to enable TFTP won't work, the box just unchecks itself again I think part of it being read only.

But thanks for posting that info! I was unable to find any live links, many of the links for firmware for this series went to websites that no longer existed.
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Offline Stonent

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Re: Possible to connect Arduino to TTL serial?
« Reply #13 on: August 16, 2013, 01:50:13 am »
Why's it such a problem to use a MAX232? You can get lots of 10 for like $5 on eBay, 5 1.0uF caps later and bang it works like a charm. Simple, easy solution. Other options are way too complex and there's no point -- just take a bit of vero or protoboard, solder on the MAX232 and the caps, feed it 5V and attach the Tx and Rx pins to the respective inputs and outputs, and you can keep this little module around whenever you need to connect TTL to Serial. They come in handy a LOT, trust me.

It's not a problem, I just didn't have any, didn't feel like waiting a week to get some, don't have 5 1.0uF caps etc.
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Offline fluxcapacitor

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Re: Possible to connect Arduino to TTL serial?
« Reply #14 on: August 16, 2013, 02:28:36 am »
Hi,read reply #11 ,you`ll need the sercomm utility to upgrade any firmware .

http://byfai.com/content/little-hacking-planex-blw54pm.html

http://www.everbesthk.com/8-download/sercomm_download.htm

you need firmware for model : IP806SM ,and the sercomm firmware upgrade utility.I think the stock firmware should flash without any problems,if not then read reply #11 ,youll need to open the firmware with a hex editor ,the instructions are in those links.
« Last Edit: August 16, 2013, 02:42:27 am by fluxcapacitor »
 

Offline Stonent

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Re: Possible to connect Arduino to TTL serial?
« Reply #15 on: August 16, 2013, 06:51:01 am »
Sorry, I meant until I had seen what you posted I was unable to find any live links to the Sercomm firmware on my own.
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