![USB Location](/helios64/img/usb/usb_ports.jpg)

## USB Controller Types

There are 3 types of USB controller available on RK3399 SoC. Each type has 2 controllers, so in total there are 6 USB controllers. Below a description of each controller type.

### Generic OHCI USB 1.1 Controller
This controller is Host only controller that is compatible with USB 1.1.

Supported speeds:

- Full Speed (12 Mbps)
- Low Speed (1.5 Mbps)

### Generic EHCI USB 2.0 Controller
This controller is Host only controller that is compatible with USB 2.0. The controller shared port with
*Generic OHCI USB 1.1 Controller* therefore any USB 1.1 device connected to the port, will be automatically routed to *Generic OHCI USB 1.1 Controller*.

Supported speed:

- High Speed (480 Mbps)

### Synopsys DesignWare USB 3.0 Dual-Role Device Controller
This controller support On-The-Go / Dual Role which means it can be configured as Host or as Device.

Supported speeds:

- Super Speed (5 Gbps)
- High Speed (480 Mbps)
- Full Speed (12 Mbps)
- Low Speed (1.5 Mbps)

This controller is connected to RK3399 Type-C PHY.

## USB on Helios64

![USB Connection](/helios64/img/usb/usb_diagram.png)

* The first USB 3.0 Dual-Role Device Controller is connected to USB Type-C connector (J15) and configured as OTG with help of [FUSB302](https://www.onsemi.com/products/interfaces/usb-type-c/fusb302).
* The second USB 3.0 Dual-Role Device Controller is connected to USB Hub 3.1 Gen 1 and configured as Host only.
* One of EHCI Controller (and OHCI Controller) is connected to M.2 socket.

### Power Budget

Each external USB port is protected by a Power Distribution switch with following current limit.

| Port | Voltage | Maximum Current | Remarks |
|------------|-------|------------------|---------|
| USB 3.0 Upper Back Panel | 5V | 900 mA | |
| USB 3.0 Lower Back Panel | 5V | 900 mA | |
| USB 3.0 Front Panel | 5V | 900 mA | |
| Type-C | 5V | 1200 mA | PDO source only |


## Type-C Functionality on Helios64

To minimize number of interfaces and cables, Helios64 combined 4 functions into the USB Type-C interface :

* Serial Console
* Display Port
* Host Mode
* Device Mode (aka DAS mode)

![USB Mux](/helios64/img/usb/usb_mux.png)

Helios64 uses an High Speed multiplexer on USB 2.0 signal. By default the USB 2.0 signal is routed to USB Serial Console.
The multiplexer can be override using [jumper P13](/helios64/jumper/#usb-consolerecovery-mode-p13) or by software via GPIO.

### Serial Console

Serial Console of Helios64 is connected to FT232 USB Serial converter and the USB 2.0 signal of the FT232 is connected to USB 2.0 signals of USB Type-C Port.

### Display Port

Using USB Type-C to DisplayPort cable, Helios64 can be connected to monitor to display Linux Desktop or others GUI applications.

![Type-c to DisplayPort](/helios64/img/usb/typec_dp.jpg)

Using USB Type-C to HDMI cable/dongle, Helios64 can be connected to a TV and used as a media center.

![Type-c to HDMI female](/helios64/img/usb/typec_hdmi_dongle.jpg)

*USB Type-C to HDMI dongle*

![Type-c to HDMI male](/helios64/img/usb/typec_hdmi.jpg)

*USB Type-C to HDMI cable*

!!! note
    - DisplayPort Alternate Mode is NOT supported on U-Boot.
    - USB Type-C to HDMI cable might not work if it used DisplayPort dual mode (DP++).

### Host Mode

Using OTG cable (Type-C to Type A female) such as,

![Type-C to Type-A female](/helios64/img/usb/typec_typea_female.jpg)

Helios64 can act as USB host and can be connected to various USB devices.

### Device Mode

Using Type-C to Type A male cable such as,

![Type-C to Type-A male](/helios64/img/usb/typec_typea_male.jpg)

Helios64 can be used as Direct Attached Storage (DAS) with the required software configuration. It can also be used as "USB eMMC reader/writer" during system recovery mode.