usb to breakout box

[smarbaga]

does anyone here redirect there software to the usb port to control there stepper, servo drives.
- i am asking because i considering making an interface to do so.
- if there is one out there i would like to see the spects and find out how well it works.
- also anyone using ethernet to printer port interface with a breakout box on the end of it.
- same .... if there is questions.
thank all

[DieGuy]

I think realtime response with any of those methods are the issue.

[ger21]

If your talking about software like TurboCNC or Mach2/3 it MUST be run using a parallel port. There will be a version of MachX, however that will control the new Gecko G100 pulse generator via usb or ethernet.

[smarbaga]

the computers os will redirect the output/input to/from the usb or ethernet port.
the users software will think it is going to the printer port.
at the far end the data will be disassembled or assembled into the data, and control bits

[ger21]

What software do you plan on using this with?

[smarbaga]

if the computers opperating system (be it - xp, me, 98 ,dos, linx) redirects the printer ports outputs or gets the printer ports inputs from somewhere somewhere else, it doesn't matter what software one is using.
the user's software only for example sends and recieves data to and from the ports handlers, the opperating system sets up the 8255 control register and moves data to and from ram to the ppc programable periferal controller.. etc etc.
i use acrobat distiller which (if i tell it to) makes all printer outputs into a pdf file.

[DieGuy]

Thsi may be true but the interupt handler is directly connected to the hardware. With a printer port converter or usb the change in line state needs to be protocol converted then transmitted where it is buffered and then delivered to the device. This is acceptable for printers and like devices.

Somebody correct me if I am wrong but with most PC CNC software, a direct handler is written to talk to the hardware to keep the speed up and the service rates high. In the case of MACH 2/3 I believe it is a dll that interface via the HAL to the printer port taking it over and providing near realtime access. In the case of turbocnc I suspect it is a piece of assembly language placed in line in the pascal code. You need to remember that the line pluse train in these software generators operate at least 25 - 40 Khz in a controlled fashion across multiple axis of motion. Time is everything here.

An interesting development is the new Gecko product which in effect is it's own single purpose computer that just takes commands via ethernet/usb and then generates it's own pulse train directly driving the motor driver. The command structure is something simplistic like move in an arc from point A to point B at X feed rate. this intermediate computer then just generated the correct pulse train to feed the drives but at a whooping rate of 2Mhz or some silly fast number like that. I can't wait to see one in action.

[jerber]

I think it's possible with some sort of external clock source. You must have a way to
read the frequency of the step pulses generated by the software and set the external clock to the same frequency.

I believe Mach3 uses the modbus protocol (wich I think DieGuy refers to) and this is
perfect for such an interface. You can find lot's of info on www.modbus.org .
I'm playing with the idea of intergrating this in a atmega16 or another atmel cpu.
Maybe anonther cnczone opensource project ?

[smarbaga]

some newer laptops have no printer ports, and newer printer are usb.
- i think the day is not far off when we will see the centronics printer port disapear altogether.
- i know there are cables out there, with micro's in them that are usb on one end and the 50 pin centronics connector on the other.
used for machines without printer ports.
- i suspect within 12 months the printer port will disapear from newer machines, just like the cassette port did, years ago, the rs232 port will go the way of the dodo as well. ( where's the pc104 bus, and scsi port )
- the theory is , why use 18-25 wires and a bulky 25 pin connector when you get away with 4, sometimes 6, also they call it a UNIVERSAL serial bus, and has a bit of smarts.
usb mice (not rs232), usb keyboards, ... goodbye printer port

[ger21]

Originally Posted by smarbaga - the theory is , why use 18-25 wires and a bulky 25 pin connector when you get away with 4, sometimes 6, also they call it a UNIVERSAL serial bus, and has a bit of smarts. usb mice (not rs232), usb keyboards, ... goodbye printer port

Because it just won't work. But you're welcome to try. Sure the parallel port will go away. But by then, there will be low priced external pulse generators like the Gecko G100, or DeskCNC,which are already available that will give far better performance and are already usb or ethernet. I suspect that there will be cheaper and faster ones as time progresses, and noone will need the parallel port anyway.

[fyffe555]

Originally Posted by smarbaga if the computers opperating system (be it - xp, me, 98 ,dos, linx) redirects the printer ports outputs or gets the printer ports inputs from somewhere somewhere else, it doesn't matter what software one is using. the user's software only for example sends and recieves data to and from the ports handlers, the opperating system sets up the 8255 control register and moves data to and from ram to the ppc programable periferal controller.. etc etc. i use acrobat distiller which (if i tell it to) makes all printer outputs into a pdf file.

No, not entirely true. Step direction management of CNC machines required a timed synchronous datastream. Printers do not.

Dos based turbocnc has direct unshared access to the hardware printer port and takes its timing from the PP hardware. Thats why , in part , it does that max speed check on startup. Its not the processor its testing and using for timing, it's the PP hardware.

Windows applications do not have direct hardware access, it's through a windows driver and that's fine for time independant apps like printer drivers where there's handshaking or driver supported protocols ( usually time independant) going on. It doesn't work for any apps that require *application* synched time events. That's why Turbocnc doesn't run well in a windows box - its using windows managed PP instead of dedicated direct access.

Mach2/3 entirely *replaces* the windows PP driver with a driver that allows the MACH2 app direct control of the port - and to take it's timing from.

USB is a serial conection. just two wires do the work and the ends manage a serial link. entirely different to a parallel port operation. And theres no reasonable means to maintain the timing (interupt handler) across usb to parallel to whatever while using the available software.

thats why Gecko have spent a year of so developing the USB or ethernet connected G100 which manages the timing off the PC.

[Al_The_Man]

There seems to be a general move by most of the automation manuf. in the direction of the Industrial Ethernet Protocol such as earlier mentiond ModBus and others like Galil and drives like AMC are using Canopen http://www.a-m-c.com/canopen/default.htm
BTW for anyone developing a Pic setup using a Modbus setup there is this program that I have found usefull for testing.
http://www.oceancontrols.com.au/modbus/modview.htm
Al.