Using ignition 7.8.2.
This system has a hand scanner for barcodes set up. We have a UDT for Scanners that normally looks like this -
The Data tag is the incoming string data of the barcode. That triggers a tag change which processes the data, and then writes it to HMI_Ack_Data_Rcvd_Echo to let the PLC know that we in fact got the the data.
Recently however, I guess a malformed barcode was scanned, as it came in to the Data tag with a bunch of unrecognized characters represented by squares. It was attempted to be processed, but when it was written back to HMI_Ack_Data_Rcvd_Echo, those unrecognized characters were written as question marks, and hence the PLC never realized it got the data back leading to a backup -
I’ve had backups happen like this before and normally the “solution” so to speak is to just copy the string from the Data tag to the HMI_Ack_Data_Rcvd_Echo tag to simulate the handshaking between server and PLC. However, in this case, I copy the string from Data and paste it into the HMI_ack_Data_Rcvd_Echo tag, it comes through as ??? instead of squares, and I am back to where I started.
My question is is there a way to paste illegal characters/squares as in the Data tag to the other tag to try to clear this? Also, any ideas on how to avoid this in the future, scripting wise? IE preventing from reading/processing characters from a PLC that I can’t even write back to it? I don’t know what sort of conditional I could even use to prevent this from happening in our tag change script.