basic.serial.javascript.rfid

Interface SignStixRfid

SignStixRfid

Javascript-to-Player interface for communicating with RFID devices connected to the Player via USB. Note that this particular interface is only supported on M12S devices and later.

This interface is built on top of 'SignStixSerial', but is simpler to use in the case of RFID scenarios such as 'Lift and Learn' or 'Place and Learn' where it's the changes in tags that are of interest, specifically a tag being placed on a pad, or lifted from a pad. These are referred to as 'events'.

Function Summary

Modifier and Type	Function and Description
void	close() Stop listening for tag information from connected RFID pads and close any open connections.
int	getNumTagsReadRecently(long periodMs) Find the number of tags that have recently (within the specified period) been read by a pad.
String	getPadsInfo() Return information about all the RFID pads that have been detected and permission granted.
String	getTagsInfo() Return information about all the tags that have been detected during the current session.
void	prepare(String jsFunctionName) Prepare to receive tag information from any connected SignStix RFID pads.
void	setSensitivity(int numReadsForAdd, int numMissesForRemove) Set the sensitivity regarding the point at which an 'added' or 'removed' event is triggered.
void	setTagReadMode(String mode) Set the tag read-mode.
int	update() Tell any attached RFID pads to read the tags in range, prompting calls to the callback specified in 'prepare'.

Function Detail

prepare

void prepare(String jsFunctionName)

Prepare to receive tag information from any connected SignStix RFID pads. On some devices, user interaction may be triggered (e.g. a pop-up dialog) to grant permission for the player device to communicate with the RFID pad.

Parameters:

jsFunctionName - the name of a Javascript function which will be called when a tag is added to (or removed from) the set of tags that are in range of the pad(s). It should take parameters as follows:

1. String eventType - "added" if the tag has just been added to the current set, or "removed" otherwise.
2. String tagId - the ID of the tag that was added.
3. String itemName - the name of the corresponding item as defined in SignStixItem, or the empty string.
4. int connId - the ID of the connection to the pad. (This can be used to differentiate between different pads, but may change from session to session.)
5. int numReads - the number of times this tag has been read during this session.

Since:

Player 3.3.0

setTagReadMode

void setTagReadMode(String mode)

Set the tag read-mode.

Parameters:

mode - "standard" (the default) means to read the built-in tag ID. Use "block" to read a tag's programmable block ID and convert it from ASCII-encoded bytes to text.

Since:

Player 3.3.0

setSensitivity

void setSensitivity(int numReadsForAdd,
                    int numMissesForRemove)

Set the sensitivity regarding the point at which an 'added' or 'removed' event is triggered. Lower numbers improve the responsiveness. Higher numbers can be used to filter out any false reads or ignore tags that are near the read-range limit and are being read intermittently.

Parameters:

numReadsForAdd - the number of times a tag must be read before the an 'added' event is triggered. Must be at least 1. The default is 2.

numMissesForRemove - the number of times a tag must fail to be read (due to being out of range) before a 'remove' event is triggered. Must be at least 1. The default is 2.

Since:

Player 3.3.0

update

int update()

Tell any attached RFID pads to read the tags in range, prompting calls to the callback specified in 'prepare'. This should be called on a regular basis for responsive performance. As a guide, every 200 ms generally works well.

Returns:

the number of RFID pads that have permission granted.

Since:

Player 3.3.0

getPadsInfo

String getPadsInfo()

Return information about all the RFID pads that have been detected and permission granted.

Returns:

JSON-formatted data about the pads. Example JSON return:

   [
     {
       "connId": 2,
       "devPath": "/dev/bus/usb/001/003",
       "vendorId": "1B4F",
       "productId": "9204"
       "numRequests": 8723,
       "numEvents": 34
     },
     ...
   ]
 

• int connId - the ID of the connection set up between the SignStix device and the pad.
• String devPath - the Linux device path of the pad e.g. "/dev/bus/usb/001/003".
• String vendorId - the USB vendor ID of the pad (in hex).
• String productId - the USB product ID of the pad (in hex).
• int numRequests - the number of times the pad has been asked to read a tag.
• int numEvents - the number of times a tag has been added to or removed from the pad.

Since:

Player 3.3.0

getTagsInfo

String getTagsInfo()

Return information about all the tags that have been detected during the current session.

Returns:

JSON-formatted data about the tags that have been read. Example JSON return:

   [
     {
       "tagId": "E5DCBD12",
       "itemName": "Sauvignon Blanc",
       "connId": 1,
       "numReads": 34,
       "millisSinceLastRead": 873
       "status": "present"
     },
     ...
   ]
 

• tagId - hex data representing the tag's ID.
• itemName - the corresponding name as defined in SignStixItem, or the empty string if not present.
• connId - the ID of the connection to the pad (can be used to differentiate between different pads, but may change from session to session).
• numReads - the number of times this tag has been read during the current session.
• millisSinceLastRead - the number of milliseconds since the tag was last read.
• status - is "present" if the millisSinceLastRead is 500 ms or less (i.e. the tag has been read within the last half-second). Otherwise the status is "absent".

Since:

Player 3.3.0

getNumTagsReadRecently

int getNumTagsReadRecently(long periodMs)

Find the number of tags that have recently (within the specified period) been read by a pad.

Parameters:

periodMs - the period (in milliseconds) up until now to consider.

Returns:

the number of tags in the current set.

Since:

Player 3.3.0

close

void close()

Stop listening for tag information from connected RFID pads and close any open connections. This should be called when communication is over to free-up resources. Do not attempt further updates after closing.

Since:

Player 3.3.0