Parallel Port to USB controller and outb()

eteck · 06-04-2009, 01:23 AM

Hi guys,

From what I've tried and read I can't use outb() or inb() to control a parallel port (which connects via usb).

Any body know how to control a parallel port for systems without a physical parallel port connector (and hence have to buy and use a parallel port to usb converter).

Thx in advance.

Matir · 06-04-2009, 07:30 PM

A quick forum search turned up: http://www.linuxquestions.org/questi...r-port-654695/

eteck · 06-04-2009, 09:30 PM

Quote:

Originally Posted by Matir

A quick forum search turned up: http://www.linuxquestions.org/questi...r-port-654695/

Yeah read that before, but doesn't really answer my question.

Matir · 06-04-2009, 09:40 PM

USB to Parallel Port adapters are supported by the usblp.c kernel driver, which provides a /dev/usb/lp* or /dev/usblp* device for each attached USB->PPT converter. You can read/write to these device files to communicate with devices that comply with IEEE 1284. outb() and inb() only work with devices that support direct port-based IO, which USB->PPT devices do not. (In fact, no USB devices that I'm aware of do, largely, I suspect, due to the ability to have up to 256 USB devices)

eteck · 06-04-2009, 09:53 PM

Quote:

Originally Posted by Matir

USB to Parallel Port adapters are supported by the usblp.c kernel driver, which provides a /dev/usb/lp* or /dev/usblp* device for each attached USB->PPT converter. You can read/write to these device files to communicate with devices that comply with IEEE 1284. outb() and inb() only work with devices that support direct port-based IO, which USB->PPT devices do not. (In fact, no USB devices that I'm aware of do, largely, I suspect, due to the ability to have up to 256 USB devices)

So how do I set/read pin values for difference BASE's?

Code:

int fd = fopen("/dev/usblp0", "w");
write(fd, X, 1);

Will that set all pins X (e.g. if X = 20, will set the BASE pins to 0b10100)?

Matir · 06-04-2009, 09:57 PM

You cannot arbitrarily set pins on these devices: they have built-in firmware to speak the IEEE-1284 for them, and speak in whole blocks back to the OS. See http://help.lockergnome.com/linux/se...ict487868.html

eteck · 06-04-2009, 10:15 PM

Quote:

Originally Posted by Matir

You cannot arbitrarily set pins on these devices: they have built-in firmware to speak the IEEE-1284 for them, and speak in whole blocks back to the OS. See http://help.lockergnome.com/linux/se...ict487868.html

So you are saying its not possible to set pins anymore? There must be a way to toggle pin 0 of the BASE. Can someone give me an example.

Marko Hyvärinen · 06-04-2009, 11:42 PM

i use also simple portcontrol software for linux console to drive my GSM modem. A thought came yo my mind that should you try telling that usb<>centronics - device that there is printer after it with ready-pin etc and then send byte-stuff to it ? You can set "pin" with boolean algebra, bit set etc...

Try something like that if you have such converter, i'd like to know also results.

Marko

TimothyEBaldwin · 06-05-2009, 06:35 AM

There are some USB parallel port adapters that can do what is required, Linux has a driver for those based on the Lucent Technologies USS-720. However the latency introduced by USB can result in poor performance.

You should use the Parport API to do any bit fiddling.

Alternatively consider using a micro-controller that has USB support.