TM
USB Topology
Introduction to USB
USB On-the-Go:
Negotiation process
Appendix A USB On-the-Go

SRP (Session Request Protocol) Negotiations

OTG-B (device) asks OTG-A (host) for a USB OTG session by
signaling in one of two ways:
Pulsing an analog data line (D+ or D-), and
Pulsing V
BUS
through a relatively high impedance ( > 281
)
Note
: The B-device pulses data line first and then
pulses V
BUS