Fuzziness In Isochronous Transfer

NTDEV
1

Hello,

I have few fuzziness over Isochronous Transfer.

For Isochronous In transfer, from device side I would send the 512 bytes(Endpoint Max. Packet size = 512), whenever In tokens reaches the Device.From driver side I specified the Packet size equal to 64 bytes, i.e for every frame it is supposed to receive the data size equal to 64.

1).During Isochronous In transfer, my driver is receiving only first 64 bytes, I am unable to receive the remaining bytes i.e(512-64).I would like to know the who has the responsibility of splitting the 512 bytes of Endpoint Max.Packet size into Packet size (i.e Specified in my driver equals to 64).

2). I would like to know the Significance of bInterval in Isochronous transfer from Driver Perspective. Since In Isochronous transfer, I am specifying the Packet size which is less than or equal to End Point Max. Packet Size that has to Transmitted in every frame.

I am using Philips Full Speed Controller…,

Thanx in Advance,
Gobinath Krishna

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2

Gobinath Krishna wrote:

Hello,

I have few fuzziness over Isochronous Transfer.

No surprise there! The DDK documentation doesn’t have a great deal of
information on this topic.

For Isochronous In transfer, from device side I would send the 512
bytes(Endpoint Max. Packet size = 512), whenever In tokens reaches the
Device.From driver side I specified the Packet size equal to 64 bytes,
i.e for every frame it is supposed to receive the data size equal to 64.

1).During Isochronous In transfer, my driver is receiving only first 64
bytes, I am unable to receive the remaining bytes i.e(512-64).I would
like to know the who has the responsibility of splitting the 512 bytes
of Endpoint Max.Packet size into Packet size (i.e Specified in my driver
equals to 64).

Your driver. That is, your driver should specify a packet size that
will accomodate the packet size from the device.

2). I would like to know the Significance of bInterval in Isochronous
transfer from Driver Perspective. Since In Isochronous transfer, I am
specifying the Packet size which is less than or equal to End Point Max.
Packet Size that has to Transmitted in every frame.

OK… We’re talking about FULL speed here, right?? Then bInterval means
nothing more than the guaranteed number of milliseconds between polls of
the device by the host bus driver. It has no impact at all on the USB
client driver.

Peter
OSR