Polling_interval property – Compaq 99875320-5 User Manual

Page 26

USB HID IntelliHead Swipe Reader

POLLING_INTERVAL PROPERTY

Property ID:

0x02

Property Type:

Byte

Length: 1

byte

Get Property:

Yes

Set Property:

Yes

Default Value:

Description:

The value is a byte that represents the devices polling interval for the Interrupt
In Endpoint. The value can be set in the range of 1 – 255 and has units of
milliseconds. The polling interval tells the host how often to poll the device
for card data packets. For example, if the polling interval is set to 10, the host
will poll the device for card data packets every 10ms. This property can be
used to speed up or slow down the time it takes to send card data to the host.
The trade-off is that speeding up the card data transfer rate increases the USB
bus bandwidth used by the device, and slowing down the card data transfer
rate decreases the USB bus bandwidth used by the device. The value of this
property, if any, will be sent to the host when the host requests the device’s
USB endpoint descriptor.

This property is stored in non-volatile memory, so it will persist when the unit
is power cycled. When this property is changed, the unit must be reset (see
Command Number 2) or power cycled to have these changes take effect.

Example Set Polling Interval property Request (Hex):

Cmd Num

Data Len

Prp ID

Prp Value

01 02

Example Set Polling Interval property Response (Hex):

Result Code Data Len

Data

00 00

Example Get Polling Interval property Request (Hex):