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The USB-C "Power In" port doubles as a USB-OTG port (or dual-role port (DRP) in USB-C speak).

Overview for the Pi 4:

The OTG hardware present on previous models of Pi is still available and it has moved to a single connection on the USB-C port. The OTG hardware is intended to be used in device-only mode on Pi 4.

The USB-C port is the only connector left that could provide USB OTG connectivity, even though the spec does not list the OTG port explicitely.

The official schematics, top left, show the USB-C Power In connector which is labelled "USB2 ONLY" and has the UUSB_D_N and UUSB_D_P data lines connected, pins A6, A7 and B6, B7, which are relevant for USB 2 (and OTG).

Transition Existing Products from USB 2.0 OTG to USB Type-C tells:

In the Type-C ecosystem, the USB 2.0 OTG device is referred as a dual-role port (DRP). A DRP is a device that can function either as a USB host or as a USB peripheral. In Type-C terminology, a USB host is called a downstream-facing port (DFP), and a USB peripheral is called an upstream-facing port (UFP).

The USB-C "Power In" port doubles as a USB-OTG port (or dual-role port (DRP) in USB-C speak).

Overview for the Pi 4:

The OTG hardware present on previous models of Pi is still available and it has moved to a single connection on the USB-C port. The OTG hardware is intended to be used in device-only mode on Pi 4.

The USB-C port is the only connector left that could provide USB OTG connectivity, even though the spec does not list the OTG port explicitely.

The official schematics, top left, show the USB-C Power In connector which is labelled "USB2 ONLY" and has the UUSB_D_N and UUSB_D_P data lines connected, pins A6, A7 and B6, B7, which are relevant for USB 2 (and OTG).

Transition Existing Products from USB 2.0 OTG to USB Type-C tells:

In the Type-C ecosystem, the USB 2.0 OTG device is referred as a dual-role port (DRP). A DRP is a device that can function either as a USB host or as a USB peripheral. In Type-C terminology, a USB host is called a downstream-facing port (DFP), and a USB peripheral is called an upstream-facing port (UFP).

The USB-C "Power In" port doubles as a USB-OTG port (or dual-role port (DRP) in USB-C speak).

Overview for the Pi 4:

The OTG hardware present on previous models of Pi is still available and it has moved to a single connection on the USB-C port. The OTG hardware is intended to be used in device-only mode on Pi 4.

The USB-C port seems to be the only connector left that could provide USB OTG connectivity. I wonder why the spec does not list the OTG port though...

The official schematics, top left, show the USB-C Power In connector which is labelled "USB2 ONLY" and has the UUSB_D_N and UUSB_D_P data lines connected, pins A6, A7 and B6, B7. The USB-C standard allows:

A device with a Type-C connector does not necessarily implement USB 3.1, USB Power Delivery, or any Alternate Mode: the Type-C connector is common to several technologies while mandating only a few of them.

In this case the schematics of the Pi 4 do not indicate that the USB 3.1 data lines (pairs of TX/RX lines) are connected, but the USB 2 lines are in fact connected.

Transition Existing Products from USB 2.0 OTG to USB Type-C tells:

In the Type-C ecosystem, the USB 2.0 OTG device is referred as a dual-role port (DRP). A DRP is a device that can function either as a USB host or as a USB peripheral. In Type-C terminology, a USB host is called a downstream-facing port (DFP), and a USB peripheral is called an upstream-facing port (UFP).

The USB-C "Power In" port doubles as a USB-OTG port (or dual-role port (DRP) in USB-C speak).

Overview for the Pi 4:

The OTG hardware present on previous models of Pi is still available and it has moved to a single connection on the USB-C port. The OTG hardware is intended to be used in device-only mode on Pi 4.

The USB-C port is the only connector left that could provide USB OTG connectivity, even though the spec does not list the OTG port explicitely.

The official schematics, top left, show the USB-C Power In connector which is labelled "USB2 ONLY" and has the UUSB_D_N and UUSB_D_P data lines connected, pins A6, A7 and B6, B7, which are relevant for USB 2 (and OTG).

Transition Existing Products from USB 2.0 OTG to USB Type-C tells:

In the Type-C ecosystem, the USB 2.0 OTG device is referred as a dual-role port (DRP). A DRP is a device that can function either as a USB host or as a USB peripheral. In Type-C terminology, a USB host is called a downstream-facing port (DFP), and a USB peripheral is called an upstream-facing port (UFP).

The USB-C port seems to be the only connector left that could provide USB OTG connectivity. I wonder why the spec does not list the OTG port though...

The official schematics, top left, show the USB-C Power In connector which is labelled "USB2 ONLY" and has the UUSB_D_N and UUSB_D_P data lines connected, pins A6, A7 and B6, B7. The USB-C standard allows:

A device with a Type-C connector does not necessarily implement USB 3.1, USB Power Delivery, or any Alternate Mode: the Type-C connector is common to several technologies while mandating only a few of them.

In this case the schematics of the Pi 4 do not indicate that the USB 3.1 data lines (pairs of TX/RX lines) are connected, but the USB 2 lines are in fact connected.

Transition Existing Products from USB 2.0 OTG to USB Type-C tells:

In the Type-C ecosystem, the USB 2.0 OTG device is referred as a dual-role port (DRP). A DRP is a device that can function either as a USB host or as a USB peripheral. In Type-C terminology, a USB host is called a downstream-facing port (DFP), and a USB peripheral is called an upstream-facing port (UFP).

The USB-C "Power In" port doubles as a USB-OTG port (or dual-role port (DRP) in USB-C speak).

Overview for the Pi 4:

The OTG hardware present on previous models of Pi is still available and it has moved to a single connection on the USB-C port. The OTG hardware is intended to be used in device-only mode on Pi 4.

The USB-C port seems to be the only connector left that could provide USB OTG connectivity. I wonder why the spec does not list the OTG port though...

The official schematics, top left, show the USB-C Power In connector which is labelled "USB2 ONLY" and has the UUSB_D_N and UUSB_D_P data lines connected, pins A6, A7 and B6, B7. The USB-C standard allows:

A device with a Type-C connector does not necessarily implement USB 3.1, USB Power Delivery, or any Alternate Mode: the Type-C connector is common to several technologies while mandating only a few of them.

In this case the schematics of the Pi 4 do not indicate that the USB 3.1 data lines (pairs of TX/RX lines) are connected, but the USB 2 lines are in fact connected.

Transition Existing Products from USB 2.0 OTG to USB Type-C tells:

In the Type-C ecosystem, the USB 2.0 OTG device is referred as a dual-role port (DRP). A DRP is a device that can function either as a USB host or as a USB peripheral. In Type-C terminology, a USB host is called a downstream-facing port (DFP), and a USB peripheral is called an upstream-facing port (UFP).