Universal Serial Bus – USB

• Universal Serial Bus – USB
• Nokia AV 2.5mm/3.5mm Connector
• Nokia Pop-Port™
• Nokia 2-mm Charging Interface

Standard hosts and standard devices

The Universal Serial Bus interface is implemented using a mini B or micro AB USB connector. The USB uses a host/peripheral architecture; a PC is the host and a Nokia device acts as the peripheral. The majority of currently sold Nokia devices support USB 2.0 Full Speed (12 MBit/s) but some devices, such as the Nokia N810 Internet Tablet, support USB High-Speed.

The following USB peripheral classes are supported, but not available simultaneously. The USB peripheral classes are available depending on the active USB mode. Nokia devices usually support three different USB modes: PC Suite, Printing & media, and Data storage. Each USB mode is represented by a different set of classes delivered by the peripheral when the USB host asks for the configuration descriptors. PC suite mode represents, in general, a set of functions of the WMC class, Printing & media represents the SICD class, and Data Storage the Mass Storage Class. The different USB modes can be selected from a menu when connecting the USB cable. The mobile device may also have a default USB mode.

Note that the availability varies between devices:

• The Wireless Mobile Communications Device Class allows developers to create a serial communication connection to a PC. Nokia PC Suite also utilizes this mode. The Abstract Control Model (ACM) function in Wireless Mobile Communications Device Class allows developers to create a serial communication connection to a PC or an accessory which supports embedded USB hosts. The Object Exchange Protocol (OBEX) function in the same class allows synchronization with PC. Nokia PC Suite also utilizes this mode.
• The Mass Storage class allows the Nokia device memory and memory card inside the mobile device to be seen as an external drive for the PC. When the memory is shared via Mass Storage, it is not accessible from the device.
• The Still Image Capture Device (SICD) class together with Picture Transfer Protocol allows the transfer of images from a Nokia device to a PC and a printer without the need for additional device drivers. Still Image Device class and PictBridge utilize the Picture Transfer Protocol.
• The PictBridge, which resides on top of Picture Transfer Protocol, allows images to be printed directly from a Nokia device to a PictBridge-compatible printer using the USB cable.
• The Media Transfer Protocol is an extension of the Picture Transfer Protocol. It allows files to be transferred between the host and the device. Its advantage, compared to Mass Storage, is that it allows simultaneous access to the same file system from the host and from the mobile device.

USB On-The-Go (OTG)

USB On-The-Go (USB OTG) changes the host/peripheral architecture. Now an OTG-enabled device can act as a host. An OTG-compatible device acts as a USB host when a USB headset is connected to the device and as a peripheral when the device is connected to a PC. USB OTG is currently available on selected Series 40 devices and the Nokia N810 Internet Tablet. OTG defines a default role; the default host is the device where the micro A USB connector is plugged in. This device sources the power on the bus. Two protocols are defined with OTG:

• Host Negotiation Protocol (HNP) and
• Session Request Protocol (SRP)

HNP is used from a device to switch the role from peripheral to host.

SRP is used by the peripheral to request power on the bus if the default host has switched it off.

The following USB Host classes are supported. For more information, see the document Series 40 Platform: USB Audio Device Requirements. Note that the availability varies between devices:

• Digital Audio Class driver supports USB 1.0 audio headsets with isochronous synchronous data, PCM Type I data, 48000 Hz sampling frequency, 16 bit, and mono for microphone, stereo for speaker. Series 40 OTG compatible devices support USB Audio Class topologies which have a headset with stereo speakers, mono microphone and a sidetone generation. Currently speaker-only or microphone-only topologies are not supported.
• The HID class driver supports the following buttons: phone mute, hook, send, drop, play/pause, stop, next track, and previous track.

In certain models the micro USB connector is also the device-charging interface, for example in the Nokia 6500, the Nokia 7900, and the Nokia 8800 Arte Edition. On the contrary, the mini USB connector cannot be used as device-charging interface. USB OTG-compatible devices, such as the Nokia N810 Internet Tablet and the Nokia 6500 Classic, can also power external accessories, but the maximum power output is limited to 100mA by Nokia. A standard PC USB host may output up to 500mA per USB port.

Examples:

• The Nokia N810 Internet Tablet has both USB 2.0 High-Speed OTG and Full OTG. Full OTG allows a role switch in host role and can actively do a role switch from peripheral role to host role. USB charging and digital audio classes are not supported. The Nokia 810 Internet Tablet can power an external accessory with a maximum of 100 mA. The tablet supports the Mass Storage class in host mode according to the Targeted Peripheral List (TPL). TPL is the list of products that a given OTG host supports. For more information, read Kate Alhola's USB blog.
• Nokia 6500 Classic has USB OTG, but supports only USB Digital Audio Class in host mode. This means that only USB Digital Audio-compatible USB peripherals can be connected to the Nokia device. Please note that Nokia 6500 Slider does not support USB OTG.

An example how a Symbian C++ application can transfer data over USB:
Serial communication over USB on S60 3rd Edition devices.

MIDP 2.0 serial communication example:
MIDP: Using Cable Connection In Nokia Devices (With Example)

Useful Resources

Forum Nokia Discussion board – Wired and Wireless interfaces

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