hardware alternative to parallel port
02 Feb 2010 23:58 #1727
by pcengines
hardware alternative to parallel port was created by pcengines
My suggestion: use the AC97 digital interface included "free" in virtually every PC chipset. Also available in individual form (e.g. by NXP, PCI to AC97 bridge).
AC97 interface is time synchronous, PCI bus mastering, and has plenty of bandwidth. 48 channels at 48 kHz pulse rate should be sufficient for most applications. The bus mastering means that the host CPU does NOT have to deal with the hardware every 25 or 50 microseconds. Audio bus mastering is not overly complex, should be manageable at the RTAI level.
The interface from AC97 to 8 channel step/dir, 16 channel digital input + 16 channel digital output can fit in a $3 CPLD.
For higher performance applications, phase angles or step counts could be transmitted instead of pulse sequences.
Please see www.pcengines.ch/ac97mot.htm for detailed design idea. I don't have time to implement this myself (not in the CNC business), but can provide support. Anyone interested ?
AC97 interface is time synchronous, PCI bus mastering, and has plenty of bandwidth. 48 channels at 48 kHz pulse rate should be sufficient for most applications. The bus mastering means that the host CPU does NOT have to deal with the hardware every 25 or 50 microseconds. Audio bus mastering is not overly complex, should be manageable at the RTAI level.
The interface from AC97 to 8 channel step/dir, 16 channel digital input + 16 channel digital output can fit in a $3 CPLD.
For higher performance applications, phase angles or step counts could be transmitted instead of pulse sequences.
Please see www.pcengines.ch/ac97mot.htm for detailed design idea. I don't have time to implement this myself (not in the CNC business), but can provide support. Anyone interested ?
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