> Note that practically all the calculations in EMC2 are done in floating > point. That may complicated your task of moving this to an FPGA.
a potential solution to this is using fixed point arithmetic. I recently worked on a project which was able to do a 4 level wavelet decomposition and reconstruction of a 2048 x 12-bit vector in something like 56ns (IIRC) on an FPGA. All of this without loss of arithmetic precision (one of the members did a formal proof of the fact). This allowed real-time streaming processing of the sensor. So I think it is doable. Some rough calculations imply that you will need to configure the logic for a minimum of 20 bits (including guard bits), but 24 is more reasonable. Figure that a general high precision setup will be able to read .0001" to .00005" and have a good 100" of overall travel. You will likely need at least one extra bit on the end as a guard bit. Also, you can play games when implementing the logic by changing the number of significant digits to keep from loosing information in round-off. > What > is the need for such a project? Most modest machine tools don't need > really fast servo loop rates, 1 KHz is usually adequate. It is possible > with a fast PCI parallel port card and a decent (2 GHz or so) CPU to do > 10 KHz update rates with my PPMC boards. (I haven't actually done this, > but I am pretty sure that it would not be a problem, based on timing > tests with slower processors.) I suspect Mesa's boards can do even better. Jon, I would love to see the results for such a test, and I would be surprised if I were alone in that; ie. knowing the upper limits to your boards. > EMC2 is already considered "hard" real time by most people, if you > choose your motherboard and set up the computer properly. > > If you are not aware of the Pico Systems and Mesa products, and think > all EMC2 users are using software generated step pulses through the > parallel port, you need to check out what has been done. I (Pico > Systems) have been making servo interfaces for EMC since 2001. true, but the FPGA could be standalone and more easy to harden than a commodity off-the-shelf PC in an industrial shop context, and might well be a lot cheaper. EBo -- ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
