2013/1/14 Alan Jhonn Aguiar Schwyn <alan...@hotmail.com>: >> From: wander.lair...@gmail.com >> Date: Mon, 14 Jan 2013 21:37:02 -0200 > >> To: pyusb-users@lists.sourceforge.net >> Subject: Re: [pyusb-users] Overflow in bulkRead >> >> 2013/1/14 Alan Jhonn Aguiar Schwyn <alan...@hotmail.com>: >> > >> > I found the problem: I try to read 2 bytes, and the device was sending >> > 3.. >> > >> > And I test that: if you request 3 (and the device gives 2) no generates >> > any >> > problem.. the size of returned package is 2.. >> > >> > Why in the other case yes? >> > >> >> The device USB controller has already built a packet with 3 bytes, if >> you request less than that, the device cannot breaks the package down, >> so it fails. > > Yes. When I say "2 bytes" i'm saying: 2 bytes + 3 bytes of header) > In my code: > > dev.read(READ_HEADER_SIZE + lenght) > >>If you are not sure about how many bytes you should >> receive, it is often better to try to read "a packet size" bytes. > > Ever read 3 bytes? And check if there are 3 or only 2? >
Every endpoint has a bMaxPacketSize field, which is the size of one packet. Try to read bMaxPacketSize bytes. -- Best Regards, Wander Lairson Costa ------------------------------------------------------------------------------ Master SQL Server Development, Administration, T-SQL, SSAS, SSIS, SSRS and more. Get SQL Server skills now (including 2012) with LearnDevNow - 200+ hours of step-by-step video tutorials by Microsoft MVPs and experts. SALE $99.99 this month only - learn more at: http://p.sf.net/sfu/learnmore_122512 _______________________________________________ pyusb-users mailing list pyusb-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pyusb-users
