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Topic: Using a cell phone cable as a cheap ($3) USB TTL (Read 7853 times) previous topic - next topic


Long story short, I used a cheap ($3 on ebay delivered) Nokia CA-42 cable knockoff as a USB to serial adapter for another project (adding a serial port to a Buffalo Linkstation Live Network attached storage LINK BELOW).

Would it be possible to do something similar for use with a boarduino?  Most of the cheap cables are based on a Prolific PL2303 (datasheet LINK BELOW) chipset which is supported under Windows and Linux.  

Seems like a great way to get a cheap USB to 3.3V TTL...


This sounds like a good idea. I bet the prices (on ebay) will jump very soon.


It should be possible, although it looks like those are strictly 3-wire serial implementations.  That means that the auto-reset feature won't work, and you'll have to push the button just like in the good old days.

Matt Elias

Apr 10, 2009, 03:45 am Last Edit: Apr 10, 2009, 04:33 am by m_elias Reason: 1
If anyone is interested, I cut the end off of a CA-42 cable and discovered the following pinout:
yellow -> common
blue -> arduino TX
green -> arduino RX
red -> unknown

I downloaded the driver from Prolific's site mentioned earlier (2nd post). Version worked for me in Vista x64. I was able to program my BBB freeduino and monitor returning serial data for debugging.

There are a couple disadvantages, the first being no 5V power to run the 'duino off of and second, you have to manually press the reset button. The second is actually a non-issue for myself as I don't like the auto-reset feature resetting my 'duino every time I start the Serial Monitor or plug in the USB cable or start the Arduino compiler. Then, there is the advantage of price, I paid just shy of $5 USD per cable shipped.

note: my cable runs at 0-3.3V on the TX line


Nice - Just ordered one from Hong Kong - $3.24 shipped.

Matt Elias

Update: I found out that the usb end of my cable is not an injection molded plug, but with some prying I could pop it open. I then proceeded to solder the red wire to a +5V contact and behold, it now powers my Arduino too!! Now if only I could get the Arduino to bake me a cake....


For those that want the 5V power or auto-reset, you may want to look into hacking one of these: http://www.dealextreme.com/details.dx/sku.2537
$6.68 shipped


I apologize, again, for my newness.  I just read this thread (thanks westfw) and the linking pages: Does that mean I would just solder the appropriate ends of this cable to... a board...somewhere? I'm confused.

Backstory: I have an arduino project, that takes Pushbutton triggers, and sends data over the USB connection.  I'd like to make more, without buying separate arduinos for each ($30) or using boardino/BBB solutions with breakout USB ($20-$25)... if I can cut my Serial connectivity cost from $12-$15 to just $3, that's a big enough deal for me to do it, I just don't understand exactly what I would be connecting where...

Thanks guys,

Matt Elias

I soldered on an end that was compatible with most of the Arduino clones out there, a BBB in my case, also compatible with the FTDI cable pinouts. See the photos, the first one is the CA-42 stock, and the second is after I have modified it.



when you say you soldered it to your BBB, where did you solder? I am a little lost there...

Matt Elias

I soldered on an end that was compatible...
See the photos, I did not solder the cable directly to my BBB, I soldered on a connector that plugs into the 6 pin header that most people would plug their FTDI USB to TTL cable or a USB BUB into.

example of FTDI cable: http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMtf8aSAtgR7DpPMdam/we00
USB BUB: http://moderndevice.com/connect.shtml



I want to clarify something....

These USB-to-Serial cables, even if they have the PL2303 chip, are they TTL compatible?

I asked because I always thought serial port specifications are not TTL compatible...
so if it is a USB-to-Serial cable, can you just connect the serial side to the Arduino? Don't we need some form of level conversion like using MAX323?


May 27, 2009, 01:01 pm Last Edit: May 27, 2009, 01:01 pm by mem Reason: 1
LiveRock, most of these cables (for example the one I linked in post #7) use the PL-2303 for USB , and a Maxim chip for the RS232 level conversion. The PL-2303 operates at logic levels that are compatible with the arduino pins. There is a datasheet here: http://user.chollian.net/~mines/pl2303.pdf

Yardley Dobon

Oct 05, 2009, 07:22 am Last Edit: Oct 05, 2009, 07:24 am by yardleydobon Reason: 1
I wrote an article for uC Hobby with step by step instructions on how to
use one of the cables with an Arduino breadboard setup. I modified the
cable to provide USB power and auto-reset. Here's a link:

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