Data request commands

These can be used to retrieve data (a Get operation) from the VTAP reader. Some of the most common data request commands are listed below. The full list of possible commands is provided in Data request commands.

Use ?r when in passive mode to request the NFC pass or card/tag payload last read. The tap data will be sent as long as it was read within the last InvalidDataCacheMS period and the request comes from an interface with a ...Source setting that permits this type of data to be sent over that interface.
Up to three serial interfaces can request and receive this cached data for a single tap, at different times, up to the InvalidDataCacheMS period. The data will not be overwritten by a more recent tap until all potential interfaces have read the tap data or the InvalidDataCacheMS period is reached. [Note: On hardware VTAP100 v4 or earlier, there is only one cache, so there is a greater risk that the data could be overwritten by a more recent tap before it has been read on all interfaces].
Use the ?type command to request the type of the NFC pass last read, along with VAS merchant ID/ ST Collector ID and ECC key slot. For cards/tags ?t is more suitable. This command is also used in passive mode only.
Example: Send type? command within 3000ms after a successful Google pass read
Copy
```
?type
```
This will result in a VTAP response, such as:

G16

This shows pass type is G for Google, Collector ID is 1 and ECC key slot used is 6.
Note: Always use ?type to extract the pass type when in passive mode. In passive mode, you cannot set a prefix/postfix for your payload to output the payload using ?r with $t$n set as prefix/postfix.
Using the %<setting> command to request the current value of any setting that is included in config.txt. This command can be used in both active and passive mode.
Example: Send %PassLED to get the value for the LED response pattern set for a successful pass read
Copy
```
%PassLED
```
This will result in a VTAP response such as:

PassLED=00FF00,100,50,2
Send a ?b command to retrieve boot information from your VTAP reader, as contained in boot.txt. This includes model, serial number, hardware and firmware version, connected expansion (if any), and ECC key slots used.
Use the ?temp command to retrieve the internal temperature (in Celsius) of the VTAP reader .
Example: Send %temp to check the internal temperature of the VTAP reader
Copy
```
?temp
```
This will result in a VTAP response such as:

40.41C