[javax-usb-devel] Fw: A question from a young researcher

[Vasilios Anagnostopoulos]

----- Original Message ----- From: Vasilios Anagnostopoulos To: [EMAIL PROTECTED] Sent: Thursday, April 22, 2004 12:37 PM Subject: Fw: A question from a young researcher I have installed the javax.usb package and I try to write a simple program for printing to the notorious HP1000 Laserjet . But I have a problem . According to the class specification , a printer class must have at least a DATA interface with one Bulk OUT or one BULK IN and one BULK OUT endpoint (plus the standard bi-directional default control endpoint ) . When I issue a getDescriptor IRP+getConfiguration descriptor I get the correct answer (according to the standard) , I am very happy . When I issue a getDescriptor IRP+getInterface ,  the device hangs . I use almost the same IRP as in getDescriptor+getConfiguration with the modifications (according to the standard)   "getDescriptor+getInterface"   bmRequestType 10000000B bRequest  GET_DESCRIPTOR wvalue 0x0400 /*Interface*/ windex 0 wvalue  9 bytes     "getDescriptor+getConfiguration"   bmRequestType 10000000B bRequest  GET_DESCRIPTOR wvalue 0x0200 /*Configuration*/ windex 0 wvalue  9 bytes   the first did not work , the second was fine . I used for wvalue (for the interface) the possible value 0x0401 because in the usbspec it says that wValue must have Descriptor type and descriptor index . No luck :-(   The most curious feature is that when I used the code from http://www-106.ibm.com/developerworks/java/library/j-usb.html   with the method testIO and called interf.getClass (which means it reads the inetrface descriptor) and so on , the answers I got were the same as in the class specification for printer devices , they were correct . The printer supports protocol 0x02 (a bidirectional endpoint in the interface) .  When I try to interf.claim() (logged as root) , the try block throws an exception .   What is the problem : Does this means that the printer has no other endpoints except the control endpoints ? Is this a violation of the specification ? Do I make something wrong ?   I use Fedora Core 1 (at home).