I have some magstripe cards that have a 9 digit(base 10) number reduced to 7 digits in base 32 to save space. (Go figure)
I need to output this in binary for use in an access control panel.
I am willing to build a small interface board. Any thoughts about any off the shelf technology before I start from scratch?
Thanks, Danno
How is the 9-digit decimal number 999999999 represented in the 7-digit base-32 format?
Since 999,999,999 fits in 32 bits (actually 30 bits), I presume that there is some advantage to using 7 5-bit groups (35 bits total) due to the physical nature of the card. What I don't understand is why they use 7 digits, when 6 was enough.
,
number
that
due to
they
There is likely an added check-sum for error detection.
just think of Hex. for example. 15 DEc is F (4 bits). so base 16 ( 16 different combo's) in every 4 bits = 2^4 so now do that for a base 32.. that is 5 bits. 32 numbers total. etc..
Yes, those are the same numbers that I got John.
But the result is only 6 digits, and they are already a 30-bit binary representation of 999999999, and no further processing is required to get the OP what he apparently wanted (just Shifts and Adds in a uP).
I was trying to find out what I was missing.
Someone has already suggested that the 7th digit is a checksum. This makes sense, possibly something like a simple XOR of the other 6.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required