transfer characters from parallel DB25 to USB 2.0 Type B

chutterb · Post by **chutterb** » Thu Nov 30, 2006 5:30 pm

We have an insturment that currently sends reports directly to a printer(HP for example). The connection/cable is a DB25 parallel port on our instrument to Centronix port on the printer.
More and more printers these days only support USB 2.0 Type B. We need to build an adapter that can plug into our DB25 parallel port and transfer characters to the printers usb port. It seems as though the AVR-USB would support this.
I have found no commercial products that can do this.
Any thoughts or ideas would be appreciated,
Aloha

Post by **christian** » Thu Nov 30, 2006 8:01 pm

Sorry, but this is not easily possible. What you want is a USB Host, not a Device. Hosts are much more complex than Devices and can therefore not be implemented in firmware. At least not on the AVR.

Look for a microcontroller with "USB To Go" hardware on chip, or combine a USB Host controller with any ordinary microcontroller.

chutterb · Post by **chutterb** » Thu Nov 30, 2006 8:30 pm

From my review of USB-OTG, there is no hub. The best analogy I know of is a digital camera that connects directly to a printer. I know there is a distinct protocol for cameras to transfer data to the printer. I know the printer has a different protocol.
Still puzzled....

Post by **christian** » Thu Nov 30, 2006 9:39 pm

What do you mean with "there is no hub"? The firmware on the USB-OTG [yes, "On The Go" is the correct term] is usually limited in the support of devices. Maybe it's usual that these OTG devices don't support hubs.

The low level protocol between cameras and printers is definitely USB. The camera takes the role of the USB host. It is possible that the printer implements a simplified device class for cameras so that the camera does not need printer drivers for all available printers. But that's the application layer.