Topic: open loop communication

By: bernie

Posted on: Jul 28 2008 at 02:18:32 AM

Hello everyone, I am a CNC operator using a Matcam 3000, 2007 model 3 axis flat bed router and I`m also a hobbyist and am building a very small 3 axis cnc router at home, also building my own stepper motor electronic boards from descrete parts only, based loosely on circuit designs scattered around the WWW. Its been great fun so far and am learning all the time.
I have not used easy dnc before but wish to do so.
Question 1: Can Easy dnc drip feed the 1/0 stream open looped :?: IE: without getting any feedback from the cnc machine.
I want to break out of the PC using a store bought USB to DB9 adapter. I believe it might contain a UART type FIFO chip within it, but haven`t pulled it apart yet.
Question 2: Would I also have to set up a simple logic chip on a board to feed back a " I AM HERE " logic pulse on a return communication line to the PC :?:
Any advice, suggestions would be appreciated .

By: Support

Posted on: Jul 28 2008 at 12:32:48 PM

You mentioned CNC so I assume your machine will contains a processor/controller. In that case easyDnc would simply transmit programs (G and M codes etc) to the CNC.

There would need to be `some` feedback from the cnc otherwise how would easyDnc know when to stop or when to send the next block of data. This would usually be handled by RS232 flow control (XonXoff or RTS/CTS) You didn`t mention what the CNC was but I imagine that it`s supplied with an on-board serial port and the software built in to control the port is already there in which case you probably just need to select the correct flow control option.

By: bernie

Posted on: Jul 30 2008 at 04:14:49 AM

Thanks for the Tip. Hopefully to make this a little clearer, when I mentioned that I was building my own electronic driver boards, this also inludes the input to the machine itself. My entire 3 axis machine is home built. So the arrangement of logic gate entry to my home built driver board decoders that handle step, dir and halt for each axis will be designed and constructed by myself to handle the 1/0 stream sent down the communication line based on the logic output from EASY DNC. I see what you mean about Xon Xoff, so a fifo will be the way to go. I am hoping that my breakout USB to DB9 has such a fifo inbuilt as this would simplify things a great deal.

By: Support

Posted on: Jul 30 2008 at 01:11:11 PM

OK, so you`re building the logic as well.

What kind of `input` are you expecting through the RS232 port ? All that RS232 can send/receive is ASCII data. Are you going to write your own CNC software that converts the ASCII into motion control signals to the motors ?

Topic: open loop communication

Reply to this topic