ThingMagic Mercury xPRESS, Руководство по платформе, Страница: 115 / 146

A D I V I S I O N O F T R I M B L E
Hardware Reference Guide
115
the xPRESS motherboard to function as a USB host using the USB OTG (on-the-go)
feature.
A host USB micro connector has a slightly different shape than a client connector (more
square) and can only be inserted in ports that are designed to accommodate it. The port
on the xPRESS platform can accommodate either a micro-A (host-side) or micro-B
(client-side) connector.
The MCU controls the maximum amount of current that can be taken from the OTG USB
interface. This is controlled by 3 lines, named D0, D1 and D2 as follows:
If MCU is off or un-powered, settings will default to 010 (charger on, 500mA current limit,
“0-1-0” in the table). This will permit reasonably fast battery charging from USB with the
reader turned off. This limits the current to the minimum a USB 2.0 port must be able to
supply. If it is known that the host has greater capacity than this, the limit can be doubled
to 1A.
D2 D1 D0 CHARGER USB current
(Limit)
0 0 0 On 100mA
0 0 1 On 1A
0 1 0 On 500mA
0 1 1 Off 500
—
A
1 0 0 Off 100mA
1 0 1 Off 1A
1 1 0 Off 500mA
1 1 1 Off 2.5mA