Host Engineering Forum
General Category => CTRIO and CTRIO2 => Topic started by: rgweber on September 15, 2008, 10:19:54 PM
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H2-CTRIO loses counts. Baldor servo outputing DLD quadrature signals to BEI, DLD to single ended 24V output converter, then to CTRIO. Baldor is following
pulse and direction out of CTRIO. Encoder feedback used to monitor the move. Servo follows pulse string (under the 25KHz max) however, BEI (w/ 1MHz rating) and the CTRIO w/ 100KHz rating, misses/adds counts. Slowing down the pulse rate improves reliability, but it doesn't seem that I should be anywhere near the limitations of the system, and I am not getting the performance I should. Looking for suggestions.
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There is a bit of a caveat in the counter performance, and this may be what you are seeing. The quad direction changes have a small window of software processing, and if another direct change occurs before that processing, we can miss stuff. It has only been a problem in very rare cases, usually involving simulated encoder inputs that have a high degree of jitter. If the servo is sitting almost still and is walking a few counts...logically, if not physically...up and down, and the servo's potential freq output is high, it may be causing back to back direction changes that we are missing.
I don't remember the exact number off the top of my head, but in general, we don't want to see a 2nd direction change any quicker than about 50 us.
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have you scoped out the logic levels?