getting binary output from a magnetic writer

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did you try libmsr?
are you trying to write an iso formatted card?

I tried libmsr but I actually can't get it to work at all -- my MSR505C doesn't show up as a physical USB device; may I ask what kernel module/option and what device (under /dev ) you used in conjunction with libmsr?

Yes, my card is an ISO card, but I would still like to be able to read and write raw arbitrary binary data.