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Originally Posted by scitobor 617
Due to the fact that I am using Linux I think it will be easier just to use a printer port to control the Victors, as the USB kits do not seem to offer Linux drivers(no surprise there). From what I have read a parrallel port should allow me to control 5-8 servos or Victors, is this correct?
-Scitobor
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A lot depends on if you are willing to use extra glue chips to make this work. With a serial in, parallel out latch, you could essentially shift in as many bits as you like and controll a TON of servos. But... ...if you are trying to more or less plumb a DB-25 connector to a printer port, you've got 6 control lines and 8 data lines.
The control lines are STROBE, AUTOFD, SLCTIN,PE & SLCT, but looking at the data sheet, PE, SLCT & ACK are inputs. SO...
I think you are limited to 11 Servos max just based on hardware. With a stable OS and some flexibility to set priorities of tasks you should be in good shape controlling 11 servos. The timing is really not that critical compared to other tasks.
Oh yeah, I would not be so sure about the lack of a Linux driver. See the quote below from
here:
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These chips have proven their abilities under multiple operating systems with FTDI’s free, top-notch virtual COM port drivers for PCs, Macs, Linux and CE operating systems. The virtual COM port drivers interface just like a serial port with extended data rates. FTDI chips are state-machine based and require no firmware. They can access an optional external EEPROM upon power-up which contains your own USB vendor and product ID should you require this feature.
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It seems to me that the FTDI chip that, based on the picture of the board, is used on the Parallax USB servo controller is THE thing that turns a standard Parallax Serial controller into a USB Serial controller.
If I am right, then the FTDI just makes the USB port generate a virtual COM port. AND FTDI claims (above) that they have FREE (as in "free beer" for you Open Source folks reading this) drivers for "multiple operating systems" including Linux.
Look at these two boards:
The only difference really is that the one on the right (the USB one) has the FDTI chip on it. I am pretty sure the the differnence is that one gets it's serial data directly an the other gets it from the FDTI chip. In that case, a Linux driver that gets you a "virtual COM" essentially IS a Linux driver for the whole kit and kaboodle.
But... ...as usual, I could be wrong.
Wrong or no, Good luck. Let us know how it turns out.
Joe J.