libftdi Archives

Subject: Re: _ftdi_determine_max_packet_size reports wrong value in some cases

From: Xiaofan Chen <xiaofanc@xxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Sun, 26 Jun 2011 19:58:06 +0800
On Sun, Jun 26, 2011 at 7:55 PM, Xiaofan Chen <xiaofanc@xxxxxxxxx> wrote:
> On Sun, Jun 26, 2011 at 7:49 PM, Алексей Косилин <kosilin75@xxxxxxxxx> wrote:
>> Thank you for the prompt reply!
>>
>> Output of the lsusb is attached to this mail.
>
> From your lsusb output you can see the following. You can see that
> the wMaxPacketSize is 64 for both EP1 IN and EP2 OUT. There is
> no alternative setting to have zero bandwitdh (zero endpoint or
> wMaxPacketSize=0, typically for ISOC device) in this case
>
>      Endpoint Descriptor:
>        bLength                 7
>        bDescriptorType         5
>        bEndpointAddress     0x81  EP 1 IN
>        bmAttributes            2
>          Transfer Type            Bulk
>          Synch Type               None
>          Usage Type               Data
>        wMaxPacketSize     0x0000  1x 0 bytes
>        bInterval               0
>      Endpoint Descriptor:
>        bLength                 7
>        bDescriptorType         5
>        bEndpointAddress     0x02  EP 2 OUT
>        bmAttributes            2
>          Transfer Type            Bulk
>          Synch Type               None
>          Usage Type               Data
>        wMaxPacketSize     0x0040  1x 64 bytes
>        bInterval               0
>
> So you should probably fix the problem in your system and not
> to change the libftdi codes.
>
> What is your system?
>

Oops, my bad, something is wrong with your device that
wMaxPacketSize for EP1 IN is zero. In that case, how
can it send data to the host?

What is your system?


-- 
Xiaofan


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