why the data length of iso transfer is always 0?

QNX Newsgroups (Archives) qdn.public.ddk.usb
1

hi,everyone
I am writing a driver for a camera ov511+.It seems all right before it
begins to transfer iso data.I called
usbd_io(urb, cam->IsoPipe, iso_cbf, cam,USBD_TIME_INFINITY);
and in the callback function iso_cbf,
usbd_urb_status( urb, &fst, &flen ) is called .but every time ,the fst is
USBD_STATUS_CMP yet the flen equals to 0. the USBD_STATUS_CMP means the
operation has completed but why the data length is 0?
Could anyone give me some tips? thanks very much

2

Is this always or only when the frame ends ?
May this is the indicator to the end of frame ?
cheers, peter

Meg Dai wrote:

hi,everyone
I am writing a driver for a camera ov511+.It seems all right before it
begins to transfer iso data.I called
usbd_io(urb, cam->IsoPipe, iso_cbf, cam,USBD_TIME_INFINITY);
and in the callback function iso_cbf,
usbd_urb_status( urb, &fst, &flen ) is called .but every time ,the fst is
USBD_STATUS_CMP yet the flen equals to 0. the USBD_STATUS_CMP means the
operation has completed but why the data length is 0?
Could anyone give me some tips? thanks very much

3

It always acts that way. I setup another iso transfer at the end of
iso_cbf so that the function will be called continually, but the result is
always the same: the status is1000000 and the length of data transferred is
0 .

“peter” <pidderw@hotmail.com> ??? news:3F830B34.4030601@hotmail.com…

Is this always or only when the frame ends ?
May this is the indicator to the end of frame ?
cheers, peter

Meg Dai wrote:
hi,everyone
I am writing a driver for a camera ov511+.It seems all right before it
begins to transfer iso data.I called
usbd_io(urb, cam->IsoPipe, iso_cbf, cam,USBD_TIME_INFINITY);
and in the callback function iso_cbf,
usbd_urb_status( urb, &fst, &flen ) is called .but every time ,the fst
is
USBD_STATUS_CMP yet the flen equals to 0. the USBD_STATUS_CMP means the
operation has completed but why the data length is 0?
Could anyone give me some tips? thanks very much

\

4

I saw this, when doing a usbd_pipe_reset or usbd_pipe_abort and then
changing the alternate/interface and restarting isochron transfers.
All transfers are USBD_URB_CMP but with 0 bytes length.
May try avoid to use usbd_abort_pipe().
cheers, peter

Meg Dai wrote:

It always acts that way. I setup another iso transfer at the end of
iso_cbf so that the function will be called continually, but the result is
always the same: the status is1000000 and the length of data transferred is
0 .

“peter” <> pidderw@hotmail.com> > ??? news:> 3F830B34.4030601@hotmail.com> …

Is this always or only when the frame ends ?
May this is the indicator to the end of frame ?
cheers, peter

Meg Dai wrote:

hi,everyone
I am writing a driver for a camera ov511+.It seems all right before it
begins to transfer iso data.I called
usbd_io(urb, cam->IsoPipe, iso_cbf, cam,USBD_TIME_INFINITY);
and in the callback function iso_cbf,
usbd_urb_status( urb, &fst, &flen ) is called .but every time ,the fst

is

USBD_STATUS_CMP yet the flen equals to 0. the USBD_STATUS_CMP means the
operation has completed but why the data length is 0?
Could anyone give me some tips? thanks very much



\

5

Hi, Peter, thanks for your help.
But in my case,it is different. In fact, after i called usbd_abort_pipe,the
return status would be 20409fa,which is not defined at all, and i have
disabled all usbd_abort_pipe, the result is still the same.Could there be
any other causes for this?
Best regards
“peter” <pidderw@hotmail.com> ??? news:3F8747A1.2010301@hotmail.com…

I saw this, when doing a usbd_pipe_reset or usbd_pipe_abort and then
changing the alternate/interface and restarting isochron transfers.
All transfers are USBD_URB_CMP but with 0 bytes length.
May try avoid to use usbd_abort_pipe().
cheers, peter

Meg Dai wrote:
It always acts that way. I setup another iso transfer at the end of
iso_cbf so that the function will be called continually, but the result
is
always the same: the status is1000000 and the length of data transferred
is
0 .

“peter” <> pidderw@hotmail.com> > ??? news:> 3F830B34.4030601@hotmail.com> …

Is this always or only when the frame ends ?
May this is the indicator to the end of frame ?
cheers, peter

Meg Dai wrote:

hi,everyone
I am writing a driver for a camera ov511+.It seems all right before it
begins to transfer iso data.I called
usbd_io(urb, cam->IsoPipe, iso_cbf, cam,USBD_TIME_INFINITY);
and in the callback function iso_cbf,
usbd_urb_status( urb, &fst, &flen ) is called .but every time ,the fst

is

USBD_STATUS_CMP yet the flen equals to 0. the USBD_STATUS_CMP means the
operation has completed but why the data length is 0?
Could anyone give me some tips? thanks very much





\

6

You are sure, that all previous transfers are terminated/completed
before you start a new transfer (usbd_io) with the same urb buffer.
e.g. if you change the alternate?
The iso_cbf is called by a separate thread wich runs in parallel
to your code. What kind of protection/synchronisation you use in
your iso_cbf to protect your urb-frame?
In my drivers, I use a single flag in the device attribute to mark
the usage of all urb buffers. If I detect this flag in my iso_cb,
I don’t restart the usbd_io() and wait until all frames are drained.
cheers, peter
Meg Dai wrote:

Hi, Peter, thanks for your help.
But in my case,it is different. In fact, after i called usbd_abort_pipe,the
return status would be 20409fa,which is not defined at all, and i have
disabled all usbd_abort_pipe, the result is still the same.Could there be
any other causes for this?
Best regards


I saw this, when doing a usbd_pipe_reset or usbd_pipe_abort and then
changing the alternate/interface and restarting isochron transfers.
All transfers are USBD_URB_CMP but with 0 bytes length.
May try avoid to use usbd_abort_pipe().
cheers, peter

Meg Dai wrote:

It always acts that way. I setup another iso transfer at the end of
iso_cbf so that the function will be called continually, but the result

is

always the same: the status is1000000 and the length of data transferred

is

0 .

“peter” <> pidderw@hotmail.com> > ??? news:> 3F830B34.4030601@hotmail.com> …


Is this always or only when the frame ends ?
May this is the indicator to the end of frame ?
cheers, peter

Meg Dai wrote:


hi,everyone
I am writing a driver for a camera ov511+.It seems all right before it
begins to transfer iso data.I called
usbd_io(urb, cam->IsoPipe, iso_cbf, cam,USBD_TIME_INFINITY);
and in the callback function iso_cbf,
usbd_urb_status( urb, &fst, &flen ) is called .but every time ,the fst


is


USBD_STATUS_CMP yet the flen equals to 0. the USBD_STATUS_CMP means the
operation has completed but why the data length is 0?
Could anyone give me some tips? thanks very much





\

7

Hi,peter.
I can get data now! I update the rtos to 6.2.0 and the result is different!
thank you very much .
I have not considered the problem of is protection for i use only one urb
one time.
“peter” <pidderw@hotmail.com> ??? news:3F89848A.9040004@hotmail.com…

You are sure, that all previous transfers are terminated/completed
before you start a new transfer (usbd_io) with the same urb buffer.
e.g. if you change the alternate?
The iso_cbf is called by a separate thread wich runs in parallel
to your code. What kind of protection/synchronisation you use in
your iso_cbf to protect your urb-frame?
In my drivers, I use a single flag in the device attribute to mark
the usage of all urb buffers. If I detect this flag in my iso_cb,
I don’t restart the usbd_io() and wait until all frames are drained.
cheers, peter
Meg Dai wrote:
Hi, Peter, thanks for your help.
But in my case,it is different. In fact, after i called
usbd_abort_pipe,the
return status would be 20409fa,which is not defined at all, and i have
disabled all usbd_abort_pipe, the result is still the same.Could there
be
any other causes for this?
Best regards


I saw this, when doing a usbd_pipe_reset or usbd_pipe_abort and then
changing the alternate/interface and restarting isochron transfers.
All transfers are USBD_URB_CMP but with 0 bytes length.
May try avoid to use usbd_abort_pipe().
cheers, peter

Meg Dai wrote:

It always acts that way. I setup another iso transfer at the end of
iso_cbf so that the function will be called continually, but the
result

is

always the same: the status is1000000 and the length of data
transferred

is

0 .

“peter” <> pidderw@hotmail.com> > ??? news:> 3F830B34.4030601@hotmail.com> …


Is this always or only when the frame ends ?
May this is the indicator to the end of frame ?
cheers, peter

Meg Dai wrote:


hi,everyone
I am writing a driver for a camera ov511+.It seems all right before
it
begins to transfer iso data.I called
usbd_io(urb, cam->IsoPipe, iso_cbf, cam,USBD_TIME_INFINITY);
and in the callback function iso_cbf,
usbd_urb_status( urb, &fst, &flen ) is called .but every time ,the
fst


is


USBD_STATUS_CMP yet the flen equals to 0. the USBD_STATUS_CMP means
the
operation has completed but why the data length is 0?
Could anyone give me some tips? thanks very much







\