Read Data from headset jack

[mrjaw]

Hi!
I have bought a credit card reader for my nexus one. This is a device that plugs into headset jack and you swipe the credit card for this or any card with magnetic striper.
I wanna know if there is a way to read the information it sent by headset jack?

This is some new for me but I need this device to read identification ID.
Tthere is any API that can be connected to headeset jack ?

Any ideas?

Thks

 

[Erel]

Can you post the link to its documentation?

 

[mrjaw]

This device doesnt have any documentation because it just a device. I am trying to use any API to read the data

 

[hackhack]

What's the model and make of the device?

 

[mrjaw]

This device is pluged into headset jack , check it here, https://squareup.com/,

I need to read the data that read this device. The problem is this device doesnt have any information just the device.

 

[hackhack]

Well you can download their app from the market - but I doubt they will provide you with information - you may well need to get a normal cardreader.

 

[thedesolatesoul]

This is a long shot but...
you can try recording the sound while you swipe the card. Open the sound file in a sound analysis program (or even audacity).
Probably you can view the data as a digital waveform, or maybe a modulated signal.
...I mean its not going to hurt to try...

 

[mrjaw]

I know it is so difficult but I need to tray. At least, I have one idea,recording the swipe and analyze the sound.

 

[rbsoft]

Many, many years ago I had written an application in VB6 that would send and receive data over a regular radio channel. This was before GPRS etc. had appeared on the scene and that used to a standard in data communication between a home base and vehicles (taxi, ambulance, etc.) Since your card reader operate via the phone jack I think it uses a similar protocol.

Basically it means you are dealing with a sort of serial communication. Your card reader will send its data (probably) as bits, in other words as 0 and 1. 0 (zero) and 1 would differ by the frequency used.

In those old days of data communication a typical standard was this:

0 = 800 Hz
1 = 2100 Hz
Baudrate: 1200

Frequencies and Baudrate might of course differ for your device, but a commonly used Motorola chip back then used these data.

Fax and old modems used the same technology. And of course them beautiful old acoustic couplers. (See link)
Acoustic coupler - Wikipedia, the free encyclopedia

There will be of course a certain prtocol involved. The software of the device will probably send some signal to initiate the transmission. The datastream received will contain some header bytes with info like length of the message etc. There might be delimiters and checksum too.

Hope this gives you a little of an idea.

Rolf

 

[ZJP]

Yes. An Fsk modem.
Need a fft library or a spectrum analyzer. Here a Java source for Android. SpecAnalyzer.java - android-spec-analyzer - Spectrum Analyzer for android - Google Project Hosting

http://code.google.com/p/moonblink/wiki/Audalyzer

JP

 

[rbsoft]

And if now someone with Java knowledge could make a library out of that...

 

[klaus]

The FFT library does exist, agraham has written one.

Best regards.

 

[Smee]

yes it uses sound alright

see here

Black Hat: Square Credit-Card Reader Hacked! - Yahoo! News

 

[Zeev Goldstein]

I know it is so difficult but I need to tray. At least, I have one idea,recording the swipe and analyze the sound.

hi,

have you managed to solve the problem ?
can you read a magnetic card from the earphone jack using this kind of reader ?
i will appreciate your help as i need an urgent help on this topic

thank you

 

[Smee]

You might find this useful

ACS Android Library - Free Downloads of Smart Card Reader Mobile Applications

 

[Zeev Goldstein]

I know it is so difficult but I need to tray. At least, I have one idea,recording the swipe and analyze the sound.

You might find this useful

ACS Android Library - Free Downloads of Smart Card Reader Mobile Applications

thanks for this.
do you have any idea on how to use this library ?
i am using b4a so not really an expert on other environments
thanks you

 

[jjcc]

There's a project using audio signal for communication
https://code.google.com/p/androino/wiki/AndroinoTerminal