On 19 September 2012 22:28, John Stewart <[email protected]> wrote:
> As I'm putting together my 2nd LinuxCNC machine, I'm putting in 2 parallel > ports in this box. > > *but* I read of pico cards, mesa cards, and other things, like the real time > component of Linux CNC and hardware interrupting giving real time errors. Both Pico and Mesa make parallel-port connected hardware, using the parport as a bus. Those should not be overlooked as they can make for easy wiring, for example, and can be driven my a laptop. However, rather than buy two parport cards, you could have one Mesa 5i25 for not a lot more money ($89). That looks like a p-port, and can act exactly like a p-port, except that it can create step pulses and measure encoders at MHz rather than kHz frequencies. Not that you _need_ MHz, but you do get a lot more speed resolution. If a p-port tops out at 10khz then the next lower speed available is 5kHz. If the 1MHz card is at 10kHz it can do 9.99kHz (motors don't like to be asked to double speed in 50uS) You can plug the 5i25 directly in to a G540. (And it will definitely drive the strange charge-pump). However, it seems a shame to waste so many pins on GND, and with a different firmware, the GND pins can be GPIO too. There is a second header for generic DB25 breakout, with all the same functions. That isn't all it can do though. The onboard FPGA is wasted on GPIO, it can do all sorts of comms. So with a different firmware the same card can drive the 7i76 stepper breakout (5 steppers, 48IO pins, VFD voltage/direction) , or the 7i77 servo breakout (6 +/-10V, 6 10Mhz encoders, 48 IO). Both of those have one port for a serial-connected additional IO board (typically 48IO, but could also be the pennant interface with more encoders, keypad and an LCD driver). Then there is the option to put all the same stuff on the second header. Or possibly just another 8 channels of 48xIO boards (384 IO channels is probably enough?) So, you could treat the 5i25 as an expensive 2-port parallel card (on steroids), but know that if you want more in the future, the potential is there. Parports are cheaper, though. But $89 falls inside my "forgotten in a week" expenditure threshold. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
