This topic provides a brief overview about USB bulk transfers. When using the USB Bulk transfer, here is a list of things to check when transaction fails.I have for a long time been wanting to do a Custom USB class driver on the RT106x devices. The USB or flash drive or USB cable has pins. These pins do different things, They are plus 5 v, negative 5 volts, data in, and data out. Bulk Transfers are used for data which are not of the type Control, Interrupt, or Isochronous. Each USB transfer is one packet, which can be up to 64 bytes if using bulk type. If you want to send more than 64 bytes, you have to use multiple packets. Com to mail flash drive or any type of files, up to 30GB for free with unlimited number of transfers. When a bulk transfer is kept in pending state in USB Host Controller driver?