I'm hoping someone can steer me in the right direction. I'm not
exactly a USB development neophyte, but I am new to USB development
on OS X. And while I've read all of the documentation and looked
through all of the examples I can find, I'm running into a problem.
First off, here's what I'm trying to do. I'm the lead developer
of the jSyncManager (http://www.jsyncmanager.org), a pure Java, Open
Source API and toolset for synchronizing PalmOS-based handhelds. The
project has been around for a long time, and has supported USB
synchronization for quite a while, but typically requires either the
Open Source jUSB API (http://jusb.sf.net), or the newer (and more
standard) javax.usb API (http://www.javax-usb.org). The protocol
stack is pure Java code.
As neither of these APIs currently exist on the Mac, I've
decided to take it upon myself to write a JNI module to access USB on
the Mac. Fortunately, the jSyncManager has always sported a plug-in
interface for accessing the underlying data transports, so this sort
of addition is pretty trivial, and doesn't require any modification
to the protocol stack. I have lots of JNI experience, USB experience
using the two Java USB APIs previously mentioned, and next to none
with IOKit.
Here's my problem: I've written a preliminary version of my
transport. It compiles fine, and appears to run fine. But for some
reason, I'm losing the very first packet of the transfer.
Here's what is supposed to be going on in the USB layer: upon
detecting the connection of a PalmOS-based device, we need to
configure the device and find the two bulk transport pipes for the
synchronization process (all of which is working very nicely BTW).
Once we're initialized the interface (creating the pipes), we need to
read a 6-byte packet, which is the header for the packet data to
follow. The problem is, on the very first packet that 6-byte packet
isn't being retrieved: I'm getting 22 bytes of packet data, without
the header.
Currently I'm using the synchronous read calls, but I've also
created a version of my code that uses the asynchronous system with
the same results. I'm priming my buffer by reading a packet of data
as soon as the pipes are initialized, so I can't imagine there being
a timing problem.
Here are the bytes I'm retrieving for the first packet:
As you can see, I'm getting the second 22 byte packet , but for
some reason I'm not getting the first 6 byte packet containing the
packet header.
Now I suppose I might be missing some control call to tell the
interface to start sending data, which javax.usb is doing for me
automatically, but this isn't apparent from the javax.usb sources.
My other thought is that there is some sort of timing issue, and that
the first packet is being lost and overwritten by the second packet
before I have a chance to read it.
Does anyone have any advice? Other than this, the library
appears to work correctly. I'm hoping to get this working soon, so
if anyone has any helpful advice, please let me know!
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Usb mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/usb/email@hidden
This email sent to email@hidden
