Specifications

Section 4. USB Communications

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 02 0A

Example Set POLLING_INTERVAL property Response (Hex):

Result Code Data Len Data

00 00

Example Get POLLING_INTERVAL property Request (Hex):

Cmd Num Data Len Prp ID

00 01 02

Example Get POLLING_INTERVAL property Response (Hex):

Result Code Data Len Prp Value

00 01 0A

MAX_PACKET_SIZE PROPERTY

Property ID: 3

Property Type: Byte

Length: 1 byte

Get Property: Yes

Set Property: Yes

Default Value: 8

Description: The value is a byte that represents the devices maximum packet size for the

Interrupt In Endpoint. The value can be set in the range of 1 – 64 and has

units of bytes. The maximum packet size tells the host the maximum size of

the Interrupt In Endpoint packets. For example, if the maximum packet size is

set to 8, the device will send HID reports in multiple packets of 8 bytes each

or less for the last packet of the report. This property can be used to speed up

or slow down the time it takes to send card data to the host. Larger packet

sizes speed up communications and smaller packet sizes slow down

communications. 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 will be sent to the host when the host requests the

device’s USB endpoint descriptor.