how to latch encoder value on an index with a PCI-6602

[gpettit]

I am currently using a PCI-6602 to read 6 encoders for a 6-axis positioner.  Because these encoder values are being used in a feedback system, I can not have them jump to zero when the index is crossed.  Instead, I would like to latch the encoder value when crossing the index.  Then, I can stop the positioner and change the encoder value and the command in a controlled way.

If I can't latch the encoder value, is it somehow possible to route (in software not hard wire) the A, B, and Z signals from one counter to a spare counter?  Then I could have one of the counters zero on an index and the other not zero.  After the index is crossed, I could stop the axis in question and read both encoders to determine how far I was from the index.  During the homing routine, I could repeat this for all 6 axes. 

I also have a PCI-6220 and a PCI-6733 in the system, if their counters would help.

I am using Linux and DDK

Many Thanks,
Greg

[Steven_C]

Hi Greg,

Thanks for your post! This can be done with DAQmx. However, if you would like to learn more about doing this with the DDK, the best place to ask this question would be through the Driver Development Kit (DDK) forum which may be found at the following link.

Driver Development Kit (DDK) Forum

http://forums.ni.com/ni/board?board.id=90

I hope this helps. Thanks Greg and have a great day!

Best regards,

Steven

[gpettit]

Hi Steven,

Thanks for the fast reply.  I have a post in the DDK group at the following link:

http://forums.ni.com/ni/board/message?board.id=90&thread.id=1085

If you get a chance could you take a look and see if you have anything to add.

Many Thanks,
Greg

[mattyG]

Hi, I have the same problem.

I am using a 6602 board to read encoder signals in quadrature mode (4x) and I am trying to implement a homing procedure. "Because the encoder values are being used in a feedback system, I can not have them jump to zero when the index is crossed.  Instead, I would like to latch the encoder value when crossing the index.  Then, I can stop the positioner and change the encoder value and the command in a controlled way."

How would you do this with DAQMx?