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Author Topic: Smooth stepper, Great for servos too, Overview and updates.  (Read 32628 times)

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Offline Chaoticone

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Smooth stepper, Great for servos too, Overview and updates.
« on: October 23, 2007, 10:23:40 PM »
Hi All,

Thank you for your interest in the SmoothStepper USB controller for Mach.  The SmoothStepper is a new USB-based controller that is meant to be a replacement for the parallel port.  It was designed to emulate the parallel port (electrically and physically), which allows for a seamless integration into existing setups.  New designs will also benefit from the very precise, fast, and clean step rates that the SmoothStepper produces.  The SmoothStepper plugin uses the same XML data that is used to configure the native parallel port version of Mach.  Except for a few unique parameters (such as maximum step frequency), all of the SmoothStepper's setup parameters come from the same setup dialogs that the parallel port version uses, such as Ports and Pins.  Even oddball setups that use something like pin 17 for the X Step signal are handled with no problem.  The SmoothStepper looks and feels just like the parallel port.  Existing breakout boards should interface with the SmoothStepper without any issues.

The SmoothStepper is powered by a Xilinx FPGA for very high performance.  In the current design, the maximum step rate is 4 MHz , but there is no reason why this couldn't be increased to 8 MHz or more if necessary.  Data is sent from the PC to the SmoothStepper in very fine segments, making it very suitable for "3D" work.  The USB chip is an FTDI FT245R.  FTDI provides a Microsoft WHQL certified driver for all versions of Windows (http://ftdichip.com/Drivers/D2XX.htm).  Driver installation is straightforward.

With the SmoothStepper, there is a single plug-in file that contains both the FPGA firmware and the Mach plug-in software.  Each time you start Mach, the firmware is downloaded to the device in the blink of an eye.  Because it is all contained in one file, there is no chance of a mismatch between the plug-in software and the FPGA firmware.  Upgrades are as simple as selecting a different plugin version.  Upgrades will be free.

The SmoothStepper has two parallel port interfaces on it.  The first port is configured with pins 2 through 9 as outputs.  The second port is a bidirectional port, allowing pins 2 through 9 to be either inputs or outputs.  The connectors are 26-pin low-profile headers, and depending upon the application, may be either male or female (but not both).  With male connectors on the top side of the board (component side), ribbon cables can connect to a breakout board or a DB25 cable.  With female headers on the bottom of the board, the SmoothStepper can plug directly onto a breakout board that has the same connector spacing for a neat cableless connection.  Be on the lookout for breakout boards that will have this capability.  The output drive from the SmoothStepper is suitable for driving opto-isolators directly (for example Geckos), so if you are on a budget, you could connect it directly.  The SmoothStepper is 3.625" x 2.75" (92mm x 70mm) in size, allowing it to fit nicely in space-limited cabinets.  When I get some time in a few days I will post a picture of it.

In addition to the two parallel ports, the SmoothStepper has pluggable screw terminals for two encoder inputs with index.  One of the two inputs is differential, and the other is single-ended.  These inputs could be used as additional discrete inputs if they are not used for encoders/MPGs.  The intended purpose of the differential encoder input is for synchronization to the spindle in threading applications.  I have designed the pieces required for this function, but have not begun integration of them yet.  It will be a priority to complete threading before the SmoothStepper is released.  There is also an expansion connector that will give the SmoothStepper the ability to expand its capabilities in the future.

Art and Brian have been running a prototype version of the SmoothStepper since the Galesburg CNC Workshop.  When Brian first received his board in the mail, he hooked it up to his laptop, and within minutes was running a machine while talking to me on Skype, and running CAM software at the same time.  I think many people will want to upgrade their existing parallel port setup, just so they can use their new laptop that does not have a parallel port.

Unfortunately I do not have a website ready to go yet.  When it is available, I will post something to this forum letting you know that it is ready.  When it is ready, the website will be http://www.Warp9TD.com/, so you can check it every once in a while if you'd like.  But don't bother for a couple weeks.

The SmoothStepper will retail for $155 USD.  I hope to get the beta test boards to the contract manufacturer this week.  Everything always seems to stretch out further than I'd like.

Many thanks to Art and Brian of Artsoft for their support in making this product a reality.  I can't count the number of e-mails and plug-in revisions that have passed back and forth.  This product won't have everything that everyone wants, but there will be expansion boards and other products in the future.  There were a lot of other people that have offered advice along the way.  The list of people to thank is actually quite long.  I'll post a big thank you someday soon.

I will do my best to answer your questions.  Hopefully this is a good start.

Greg Cary
Warp9 Tech Design, Inc.
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