^RFR,^FN1,^HV1 not sending output to computer

问题

I'm attempting to read the TID bank of the current (Class 1 Generation 2) RFID tag sitting under the print-head in a Zebra RZ400 (running the latest firmware V53.17.22Z). I'm connected via USB.

I'm using the "Direct Communication" program in the Zebra Setup Utilities tool.

This is my program, annotated:

^XA             Start program
^RS8            Set RFID mode to Class 1 Gen 2
^RFR,H,0,8,2    Read the first 8 bytes of the TID bank as a Hexadecimal string
^FN1            Store the data into Memory Field #1
^FS             End Field
^HV1,,Foo       Transfer the contents of Memory Field #2 to the Host PC
^FS             End Field
^XZ             End program

When I run this, I do not get any output in the "Data received" window.

However, if I append a command like ^HH to the end (after the ^XZ) and re-run the program then the previous expected output will appear (followed by the output of ^HH). I need to keep on re-running the commands to get the previous output, making it impossible to see the current TID value.

It's as though the printer isn't flushing its output buffer until I run ^HH - other commands work temperamentally. The ^HH command isn't appropriate for my application because of the sheer amount of data it produces.

Is there some command that forces a flush?

回答1:

I need to learn to read the documentation.

The ^HV command has 5 parameters. The sample code I based my program off only provides the first 3 parameters and I didn't think that the other parameters were relevant - mostly because Zebra gave the key parameter the nonobvious name "command applies to":

^HV(fieldNumber),(byteCount),(header),(terminator),(commandAppliesTo)

While I had set fieldNumber, byteCount, and header correctly (I ignored terminator) I completely overlooked the commandAppliesTo parameter, which states:

When ^PQ is greater than 1 or if a void label occurs, send one response for a label format or one for every label printed.

Accepted Values:

• F = Format
• L = Label

Default Value: F

So when you don't specify a value it defaults to F which means it will return the data only when the entire job has completed, by changing it to L I get a response for each label that is printed.

Here's my final working command:

^XA
^RS8
^RFR,H,0,8,2
^FN1
^FS
^HV1,256,HEADER,TERMINATOR,L
^FS
^XZ

Which gets me output like this:

HEADERE28011302000240CTERMINATORHEADERE28011302000241CTERMINATORHEADERE28011302000242CTERMINATOR

Sorted :)

来源：https://stackoverflow.com/questions/36642368/rfr-fn1-hv1-not-sending-output-to-computer