Dave Caroline wrote: > The amount of data one could put in a USB microframe, may allow for > more loops per frame so make it easier > I can see some ways that one could export the software step generation to a USB parallel port. Both the FTDI2232 and the Cypress 7C68013 (EZ-USB FX2 chip) can take a USB frame and crank it out byte by byte to an 8-bit output. I think the FTDI would need an external "pacer", the Cypress chip could be made to pump out bytes at a programmable rate. If EMC2 could be set up to schedule the base thread at some rate to keep in sync with the frames sent to the USB peripheral, it would pretty much solve the disappearing parallel port problem. If we could come up with a scheme to emulate several hundred dispatches of the base thread to send one big packet of parallel port data writes to the USB device, it would probably reduce CPU overhead and even allow increased step pulse rates, while solving the par port crisis.
The FTDI chip is a pretty fixed-purpose device, but it can pump data to/from a FIFO at high rates. The Cypress chip has an 8051 on it, but that is used primarily to set up the hundreds of control registers on it. It can autonomously pump out data as 8- or 16-bit words, and can do a lot of flow-control, handshaking, or just fixed-rate throttling of the data. I am going to be doing some work at "work" with the Cypress chip, I just got in a little board with it. A complete set of open-source tools is available for it. I will be learning how to use it under NON-RT Linux, and I don't know how much trouble there'd be in communicating with it from the real-time side. Obviously, sharing the system's USB controller between RT and non-RT is non-trivial. Jon ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
