Hi all This might expose my ignorance ;-) and I'm not wanting anyone to do in-depth calculations for me..
In the days of ISA cards, the 8255 was quite popular, but now we're onto PCI and PCIe So, if one looks at the Mesa 5i25, it can read encoders because presumably because the FPGA is doing the counting. Now, if I used one pci-bridge 8255 type card and used all the I/O (A,B,C) to support 3 encoders, could I use, say a Pic processor to read the encoder and convert to 8bit data, and then; These 8bits are presented to the 8255 ports so Lcnc can do a snapshot read of the encoder values to close a servo loop. With 8bit counters on the encoders, would Lcnc read the encoders fast enough to run a servo based machine comparable to an open loop stepper system? Obviously it has to read before roll-over or all is lost So, lets say the encoder provides 5um linear resolution on an axis, moving at 10m/min (32ft/min or 0.05Furlong/min ;-) = 10 000 000um/5um /min = 2 000 000 counts/min = 33 333Hz counter rate With a /256 pic counter, roll-over will be at 130Hz or every 7.7ms Could Lcnc cope with that? Roland _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
