Scanning Barcode!

Hi guys
I collect information from some individuals in one single Interview and each one of them has his own Barcode
Sometimes the same Barcode is repeated and scanned twice
Is there any way to prevent this
thank you

In the form, there should be one variable to scan the barcode. If there are 2, then a calculate field could be created with a note showing the user that 2 barcodes have been scanned and one should be deleted.


Welcome to the ODK forum, @hogir.mir! We're glad you're here. When you get a chance, please introduce yourself on this forum thread. I'd also encourage you to add a real picture as your avatar because it helps build community!

Within a single form, if you are scanning multiple barcodes, then it should be possible to check for duplicates. @Lal_S has a good suggestion. It may be useful to also use a constraint but you would want to also add a constraint_message so that the user knows the issue preventing continuing is a duplicate barcode value.