User Guide

Section 4. USB Communications

SERIAL_NUM PROPERTY

Property ID: 1

Property Type: String

Length: 0 – 15 bytes

Get Property: Yes

Set Property: Yes

Default Value: The default value is no string with a length of zero.

Description: The value is an ASCII string that represents the device’s serial number.

This string can be 0 – 15 bytes long. This property is stored in non-volatile EEPROM memory

so it will not change when the unit is power cycled. The value of this property, if any, will be

sent to the host when the host requests the USB string descriptor. When this property is

changed, the unit must be power cycled to have these changes take effect for the USB descriptor.

If a value other than the default value is desired, it can be set by the factory upon request.

Examples follow.

Example Set SERIAL_NUM property Request (Hex):

Cmd Num Data Len Prp ID Prp Value

01 04 01 31 32 33

Example Set SERIAL_NUM property Response (Hex):

Result Code Data Len Data

00 00

Example Get SERIAL_NUM property Request (Hex):

Cmd Num Data Len Prp ID

00 01 01

Example Get SERIAL_NUM property Response (Hex):

Result Code Data Len Prp Value

00 03 31 32 33

POLLING_INTERVAL PROPERTY

Property ID: 2

Property Type: Byte

Length: 1 byte

Get Property: Yes

Set Property: Yes

Default Value: 10

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. This property is stored in non-volatile EEPROM

memory so it will not change when the unit is power cycled. The value of this property, if any,