Ruigu Electronic

USB 2.0 OTG supports dual roles

2025-11-18

Portable devices using USB 2.0 OTG determine their role as either a host or a standard device via the ID pin. By grounding (GND) the ID pin, the OTG product functions as a USB host, supplying power to connected USB peripherals. Conversely, the OTG device operates as a USB peripheral. The table shows pin assignments for sockets and plugs. The ID pin on the plug has two modes: grounded or unconnected, allowing selection between host or peripheral functionality.

Pin Name Cable Color Description
1 VBUS Red +5V Power Supply
2 D- White Differential Data –
3 D+ Green Differential Data +
4 ID N/A Identifies opposite interface type
Host: Grounded
Device: Unconnected
5 GND Black Ground
When migrating from USB 2.0 products to Type-C products, USB 3.1 signals are not required. Therefore, keep them disconnected (electrically isolated) on the printed circuit board (PCB). Represent USB 3.1 contacts as normally closed (NC) contacts within the Type-C receptacle.

When functioning as a USB device, portable USB 2.0 OTG products monitor VBUS to determine if connected to a USB host or external charger (e.g., phone plugged into power adapter). Using USB Battery Charging 1.2 (BC1.2) charging specifications or proprietary methods, portable products may request power exceeding USB 2.0’s default 2.5 watts to enable faster charging times.