Decode audio from a credit card reader

Question

I got a credit card reader that plugs into the microphone jack from my bank, and they provide apps for android and MacOS to receive payments this way. I don’t have any of these systems nor the need to accept payments, but I am curious about the device. I can record the sound on my laptop. So: Is there a Linux program that can decode this signal?

Found a C library here, but did not get it to read the Data I have: https://github.com/ieatlint/mslib — Joachim Breitner, Nov 22 '12 at 18:40

score 4 · Accepted Answer · answered Nov 22 '12 at 19:25

Thanks to the other answers I found the right words to search for and found mslib via the authors blog and, after some adjustments, got it to read data from my reader.

The library comes with a small test program that can read files created by:

arecord  -c 1 -N -r48000 -f S16_LE -i -v

score 2 · Answer 2 · answered Nov 20 '12 at 23:32

2

This is probably doing the same thing as the Square audio-input based card readers; using the equivalent of a tape head to read the information as audio. Someone has written some code that's available on GitHub for decoding this data.

answered Nov 20 '12 at 23:32

Brian Campbell

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Thanks for the link. I’ll have a look, but it might not be easy to get it to run outside an android environment. – Joachim Breitner Nov 21 '12 at 20:29

Decode audio from a credit card reader

2 Answers2