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CHAPTER 7 READER-HOST PROTOCOL EXTENSIONS FOR BATTERY POWERED BACKSCATTER TAGS
NANOSCANNER READER USER GUIDE • DOC # 8101029-000 REV A 94
© 2003 Alien Technology™
Sensor Commands
The sensor commands deal exclusively with a tag’s onboard sensor.
G
ET SENSORVALUE
Get SensorValue will return the sensor’s current value. If the sensor was already
switched off, this command will start the sensor before returning a value, which
may take up to 1 second. Sensors will automatically be switched off two seconds
after this command has been completed in order to preserve the battery life of
the tag.
Typically the tag has no knowledge of the type of sensor attached to it.
Consequently this command simply returns the raw number as returned by the
sensor. No attempt is made to process this number into a humanly
understandable form.
Note: Please refer to the Nanoscanner Tag Guide for detailed descriptions of to
format of raw sensor values. Because there are many different types of sensors
attached to the Nanoscanner tags, the format of the raw sensor values may
change due to the type of data being acquired. All details can be found in this
separate guide.
Example
Command
Response
>Get SensorValue
>SensorValue = 4539
Logging Commands
These commands control the automatic logging of sensor data into the tags
memory. Once set up, a tag can be removed from an RF field and still have
sensor data logged periodically to memory. Bringing the tag back into an RF field
will allow the memory to be retrieved and examined.
G
ET LOGGINGMODE
S
ET LOGGINGMODE
The automatic, time based logging of sensor data to a tag memory is controlled
by setting the logging mode on the tag.
Setting a logging mode to OFF will turn off all automatic logging.
Setting a logging mode to ON will turn on the automatic logging as defined by the
logging interval command. Turning on the logging mode like this will not erase
the tag’s memory; it will simply cause logged data to be appended to the current
memory store. (Use the clear memory command to erase the memory before
logging).