FSK and mag stripe reading

[Le Atatateur]

Not directly related to arduino, but I saw several topics in this group describing iOS FSK modem working with arduino devices.

I'm currently working on iOS program to read magnetic stripe cards with a simple device, consisting of magnetic head, connected directly to audio jack.

I wonder if you guys can help me with this.

I already have a working prototype, but percent of good reads is very small (less than 30%, I think). And for iPhone 5, for some reason, I cannot get a single good reading.