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hkplus

Contributor

Registered: 2015-01-07

Posts: 127

HID 37 Bit on AT5577 w/ 3 data blocks

Can anyone clarify how to create a 37 bit format on AT5577 using just three datablocks + the radio block?  I know that you have up to 37 bits of data available in the 3 data block HID formats, but usually there is a bit marker in the upper blocks that tells the reader where the first data bit starts.  If you need to represent 37 bits, you have no where to put the start bit.  I was reading in the sticky post for HID in this forum, that you can change the preamble or customer code to use all of the 37 bits just for data...anyone have experience with generating this HID 37 bit format?  I have done it in 6 block extended formats, but not with 3 data block format.

Thanks, HKPLUS!

hkplus

Contributor

Registered: 2015-01-07

Posts: 127

Re: HID 37 Bit on AT5577 w/ 3 data blocks

On second thought, I just got a ProxMark in today... There should be commands to demod an HID 37 bit card and look at it's Manchester encoding correct?

iceman

Administrator

Registered: 2013-04-25

Posts: 9,538

Website

Re: HID 37 Bit on AT5577 w/ 3 data blocks

try the "lf search"

hkplus

Contributor

Registered: 2015-01-07

Posts: 127

Re: HID 37 Bit on AT5577 w/ 3 data blocks

try the "lf search"

LF search finds this:

Reading 30000 bytes from device memory
Data fetched         
Samples @ 8 bits/smpl, decimation 1:1           
NOTE: some demods output possible binary
  if it finds something that looks like a tag         
False Positives ARE possible
Checking for known tags:
HID Prox TAG ID: 0390094ca (19045) - Format Len: 37bit - FC: 912 - Card: 19045         
Valid HID Prox ID Found! 

How do I get the Manchester encoding?

Last edited by hkplus (2015-07-23 16:08:28)

hkplus

Contributor

Registered: 2015-01-07

Posts: 127

Re: HID 37 Bit on AT5577 w/ 3 data blocks

I found exactly what I needed...

lf search
data printdemodbuffer x

Nice tool!