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Section 4. USB Communications
75
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,