Topic: Is Drip Feed - Hi Baud w/ USB possible?

By: Guest

Posted on: Sep 1 2009 at 07:57:23 PM

Just got a Mac mini, and am excited about the possibility of replacing my existing windows DNC. I need to be able to drip feed large programs (400mb) at the max baud-rate (115200) that my cnc will allow. Is this possible from a USB port?

I have a USB to RS-232 Cable, and have installed the drivers, I am getting some limited communication, but I have yet to get the settings tweaked to really run in drip feed mode. Any help would be appreciated - Thanks!

By: Guest

Posted on: Sep 2 2009 at 12:25:33 PM

Hi baud rate will need very efficient flow control - if the cnc is able to use RTS/CTS flow control during drip feeding then that is efficient.

However, xOn/xOff flow control is not efficient. The USB has very large transmit buffers which can cause buffer overflow in the CNC.

Try it cutting air to se if it goes. You may find that a lower baud rate actually works better.

By: Another Guest,

Posted on: Jan 24 2010 at 12:47:20 PM

Ok,

This is highly disapointing.. Even with the more modern chipsets such as the serial gear that support 8 simultaneous 921.6Kbps transfer rates? The one I currently have only supports about 230k.. I am trying to migrate to windows 7 because windows XP doesn't support enough ram for the huge files I need to edit. I need the 115.2 k for large files that otherwise take 15 minutes or more to transfer at 38k..The wireless bluetooth works excellent on an older PC, tested 5meg files, flawless both ways, 115.2k but on windows 7 with this older model USB 8 port, I am getting just that, buffer overflow issues.

I am still planning on trying a better model hub to see if by some miracle...??

By: Another Guest,

Posted on: Jan 24 2010 at 01:12:55 PM

oh, also to the original poster, keep in mind 6 feet is the max length supported at 115.2 even with shielded wires according to the haas manual. Wireless is what I am attempting. And like I said, it works great on a pc with a real com port built into the motherboard.. If I can only get a descent usb to serial hub I may be in business..?

By: Another Guest,

Posted on: Jan 24 2010 at 01:13:55 PM

Oh, one more question, can RTS/CTS mode be used for non dnc file transfers?

By: Support,

Posted on: Jan 25 2010 at 09:53:19 PM

..... can RTS/CTS mode be used for non dnc file transfers?

easyDnc is quite happy doing that so check whether the CNC is capable of it. If it has an RTS/CTS option then it should work.

By: Support,

Posted on: Jan 25 2010 at 09:56:54 PM

..... it works great on a pc with a real com port built into the motherboard

The problem is XOnXOff flow control. When the CNC buffer begins to fill the CNC tells the computer to stop sending data. But windows can't stop data that's already in the com port hardware.

In the case of a true com port that's just 16 bytes (and even that can be too much for some CNC)

But USB has 100's of bytes that are beyond the control of XOnXOff flow control and none of those bytes can be stopped - they land in the buffer causing the overflow.

That's why old computers with proper com ports are just better at DNC that new ones.

Topic: Is Drip Feed - Hi Baud w/ USB possible?

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