Hardware configuration and functionality

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4.9

Mini-USB connector

The mini-USB connector provides both data management features as well as board supply

operations (board supply and battery pack recharge), see Figure 10 and Table 4.

Figure 10.

Standard Mini-USB connector

This standard connector is defined as part of the USB-OTG (USB On The Go)

enhancement. It features a single connector type (A or B) and peer-to-peer operations.

The configuration present on the STR750-MAP is Type B, as pin 4 is not connected (NC in

the table).

The USB-OTG is a supplement to the USB 2.0 (or USB 1.0) specifications that allow USB

devices to have more flexibility in managing USB connections.

As known, the standard USB (USB 1.1/2.0) uses Master/Slave architecture. A USB host

acts as a Master and a USB peripheral (aka USB Device) acts as a Slave. Only the USB

host can schedule the configuration and data transfers over the link, while the USB

peripherals cannot initiate data transfers. They only respond to instructions given by a Host.

The USB-OTG compatible devices are able to initiate the session, control the connection

and exchange Host/Peripheral roles between each other.

With this new architecture, two new protocols are introduced: SRP (Session Request

Protocol) and HNP (Host Negotiation Protocol).

Two new classes of devices are defined: OTG A-device and OTG B-device. This

terminology defines which side supplies power (VBUS) to the link. The OTG A-device is a

supplier and an OTG B-device (our case) is a consumer. The default link configuration is

that A-device is Host and B-device is a Peripheral (this may be reversed later by using HNP).

These devices are fully backward compliant with USB 1.1/2.0 and behave as standard USB

Hosts or Peripherals when connected to standard (no OTG) USB devices.

Table 4.

Pins and signals correspondence for the Mini-USB connector

Pin number

Name

Colour

Notes

1

VBus

Red

Power

2

D-

White

Data -

3

D+

Green

Data +

4

ID

-

Type A – GND/Type B - NC

5GND

Black

Ground