Simplify the following text for a Grade 8 native English-speaking person.
Original: The host controller polls the bus for traffic , usually in a round-robin fashion , so no USB device can transfer any data on the bus without an explicit request from the host controller .
Simplified: The host controller directs traffic flow to devices , so no USB device can transfer any data on the bus without an explicit request from the host controller . In USB 2.0 , the host controller polls the bus for traffic , usually in a round-robin fashion .