Android bulkTransfer return -1 when read data but there is really some data in the buffer

Question

I write a app in galaxy tab p7300 to communicate with a key (scsi device) via otg cable. I can read data first time with bulkTransfer(),but can not the next time . Then I u

Answer 1

Its too late to post a solution , but in case in future someone needs help about it can get an answer from here.

I faced the same issue. I was using Android (Samsung galaxy s3) as usb host device. I figured out about the read endpoint and write endpoint not trasferring data using USB BulkTransfer. I tried to switch the endpoints for host mode case, it recognized and successfully write/read the data.

 mReadEndpoint = mDataInterface.getEndpoint(0);// tweaking endpoints // 1 was for read and 0 was for write
 mWriteEndpoint = mDataInterface.getEndpoint(1);

P.S there is an application available for android named "USB device info". It helped me a lot in understanding interfaces and endpoints of my usb device.