Android USB Host - bulkTransfer() is losing data

UsbConnection.bulktransfer(...) is buggy. Use UsbRequest.queue(...) Api.

Many people has reported that using bulktransfer directly fails around 1% or 2% of the input transfers.

Just to clarify a few of the approaches I tried...The USB code ran in it's own thread and was given max priority (no luck) - I tried API calls, libUSB, native C, and other methods (no luck) - I buffered, and polled, and queued (no luck) - ultimately I decided Android could not handle USB data at 'high speed' (constant 3.2MB/sec w/ no flow control). I built an 8MB hardware FIFO buffer into my design to make up for it. (If you think you have an answer, come up with something that feeds data in at 3.2MB/sec and see if Android can handle it without ANY hiccups. I'm pretty sure it can't.)

In Nexus Media Importer I can consistently push through about 9MB/s, so it is possible. I'm not sure if you have control of the source, but you may want to break the feed into 16K blocks with some sort of sequenced header so you can detect missing blocks and corruption.

Also, you are not checking for len < 0. I'm not sure what will have if the underlying stack gets a NAK or NYET from the other end. I get this enough that I have recovery code to handle this.

I have looked long and hard for a way to offset the bulkTransfer destination buffer, but I have yet to find it. FYI: USBRequest.queue() does not respect the ByteBuffer.position().

I'm kind of surprised we can do 16K on bulkTransfer anyway. According to the USB 2.0 spec, the max is supposed to be 512 bytes for a bulkTransfer endpoint. Is Android bundling the the bulkTransfers, or are we breaking the rules?