Hi

Is there any difference if we send 18 bytes of data instead of 8 bytes
when host requests for device
descriptors after reset.

Can anybody explain what exactly is happening here

host - > reset
host -> request for device descriptors
device -> responding with 18 bytes of device descriptor
host -> reset
device -> set address to 4
host -> reset

Please note that acks are present but not mentioned. There is no nack
either from device or host.

Instead of another request form host for device descriptors its issuing
reset.

After set_address there is 549.673 ms silence and then host is sending
reset.

Please help

Thanks in advance.

regards

Everything mentioned in your mail seems fine other than the 500 ms pause. The host first requests the device descriptor, it requires at least 8 bytes. You can send 18 but all the host is after is the control endpoint size held within the first 8 bytes. It might be best now if you post the 18 bytes of information that you return as im sure this is why the host is waiting so long. Thanks Steve Sponsor me online for the Flora London Marathon http://www.justgiving.com/gosteve

Steve

18 bytes as device descriptor,

0x12, // bLength
0x01, // Device Descr
0x00, // bcdUSB(lo)
0x02, // bcdUSB(hi)
0x00, // bDeviceClass
0x00, // bDeviceSubClass
0x00, // bDeviceProtocol
0x40, // bMaxPacketSize0
0x3f, // idVendor(lo)
0x05, // idVendor(hi)
0x55, // idProduct(lo)
0x00, // idProduct(hi)
0x00, // bcdDevice(lo)
0x01, // bcdDevice(hi)
0x01, // iManufacturer
0x02, // iProduct
0x03, // iSerialNumber
0x01 // bNumConfigurations

regards




Steve wrote:

Yes. You only send what the host requests or less. If the host requests
less than 18 bytes, sending 18 bytes is an error.



Up to this point, it is a valid sequence, including the 500 mSec wait
mentioned below.



The most common reason for a reset following a set address is that you are
not listening on address 4 and the host gives up trying to talk to you and
resets you hoping your behavior will improve.



Do note that the host will NEVER NAK.

Marc Reinig
System Solutions