On Mon, 2012-02-06 at 12:29 -0500, Erik Friesen wrote: > I am not so sure about the parallel port and encoder idea though, the > encoders I see are up to 1000 per rev, that requires a pretty fast base > period to handle that, not? <2us ?
In reference to my reply, I suggested that using the parallel port for encoders, but only if the encoder pulse rate is similar to the step rate. An FPGA PCI or parallel port board would be needed for decent encoder rates. > I also am not very clear on emc2 capability to manage analog inputs, it > seems easier to offload the deciding to an external mcu of some sort. > Also, how would emc2 handle encoders with steppers? In the normal stepper configuration file, the position command and the position feedback are software "shorted" together. core_stepper.hal ~~~~~~~~~~~~~~~~~~~~~~~ ... 25 # connect position feedback from step generators 26 # to motion module 27 net Xpos-fb stepgen.0.position-fb => axis.0.motor-pos-fb 28 net Ypos-fb stepgen.1.position-fb => axis.1.motor-pos-fb 29 net Zpos-fb stepgen.2.position-fb => axis.2.motor-pos-fb ... ~~~~~~~~~~~~~~~~~~~~~~~ This is because when a step is sent out, it is assumed that the step completes properly, and besides, a normal stepper system has no way of providing feedback. I haven't worked on a stepper system with encoders, but I think one replaces the above stepgen feedback with the encoder output. This link indicates there is are example files somewhere?: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Steppers_With_Encoders For the cost, this may be a good analog trip indicator: http://www.sparkfun.com/products/9147 The biggest problem might be in conditioning the analog signal to a 0 - 5 Volt range. One could use the USB connection as is, or change the program to just send out a one bit or watchdog signal. Being a microprocessor, the trip conditions could be quite sophisticated. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
