In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Bongo wrote:

Hi Stef,
 

it would appear that you are uncertain of a few items.  Suggest that you google wiegand, I cannot recall exact timing, but it is slow.  You need to use pullups, suggest 5 to 10 k, to 5 volts.  The reader will pull down on a data bit, and this is what needs to be read.

 

There is considerable difference in output from all the different weigand devices in the market.  The only real simularity is the fact that one of the data lines pulled low =  0, and the other, 1.

 

This is due to the original need to read wiegand cards.  The continued use of the system (as a data transmission medium) long after the demise of the wiegand card is a sad reflection on the (access control) industry.

 

If it was me, the first thing I would do is examine the reader output on a duel channel scope to get the timing and bit sequences.  If no scope, write a program for the SX to log and record a read.  Debug is great for this type of fast and dirty bit v time examination.  Set an interrupt (2 t's) for 100uS, and increment a register every interrupt until a bit pulls a data line low.  As wiegand is so slow, you will need a multi byte setup.

 

Hope this helps,  bongo

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