Bulk Transfer In Usb In Houston
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FAQ
USB 2.0 transfers data at a top speed of 480 megabits per second (Mbps), while USB 3.0 can transfer data at up to 5 gigabits per second (Gbps). You can identify USB 3.0 connectors by their blue colour and initials SS, which stand for 'SuperSpeed'.
USB Full speed has a speed of 12 MBit/second = 1,5 MByte/s. But within these 12 MBit also a lot of extra data is transmitted which is not payload, like , endpoint address, CRC5, CRC16, Acknowledge, SOF + EOF packets, etc.. Additionally the bus manager reserves 10% of a frame for Control Transfers.
The four kinds of pipes that communicate with the four kinds of USB endpoints are: Control. Control pipes are used primarily to send commands and retrieve status. Bulk. Bulk pipes are used primarily for data transfer. Interrupt. Isochronous.
Maximum packet size of a bulk endpoint depends on the bus speed of the device. For full speed, high speed, and SuperSpeed; the maximum packet sizes are 64, 512, and 1024 bytes respectively.
There are various FAT formats as well, including FAT/FAT16 (max volume size 4GB, max file size 2GB), and FAT32 (max volume size 2TB, max file size 4GB).
Bulk Transfers. Bulk Transfers are used for data which are not of the type Control, Interrupt, or Isochronous. Reliable exchange of data is ensured at the hardware level using error detection. Data are transferred in the same manner as in Interrupt Transfers, but have no defined polling rate.
USB data is transmitted serially (as they name implies) on a single had duplex 0/5V differential pair. On USB-2, is uses NRZI encoding, with bit stuffing so after 5 consecutive 1s a 0 is inserted to ensure transitions. The data rate is 1 MHZ for low speed, 12 MHz for full speed, and 480 MHz for high speed.
How is data sent across USB? When a peripheral device is attached via USB, the host computer will detect what kind of device it is and automatically load a driver that allows the device to function. Data is transferred between the two devices in small amounts known as 'packets'.
USB has four transfer types depending on the data. They are called Control, Bulk, Interrupt, and Isochronous types.
