Hello,

I recommend for first call this on OB1 or required FB/FC. Next recommendation is to create instance DB to FB2 and use this as signal status check. I expect instance DB use internally also other important data for correct FB2 functionality probably. Your DB as receive buffer  (DB20) can have Array of bytes structure long enough for max expected number of receive bytes. One question, what reason save first received byte to 3-rd byte in recv DB -> DBB_NO? With your presented settings in RCV block, set EN_R to true is enough for test start. You can make basic condition (set some M memory or Q LED output) if NDR is true, then you will have clear info that bytes are arrived. One maybe first basic check are also LEDs on CP, in your case only RX can be monitored visually and after read RFID it can flash for while (data are comming). Make tests and come with results.

Update: meanwhile after your screenshot, settings on CP340 looks ok to me (as receive condition).

Update2: pls don't change your already made post because now I see other infos and don't know what is now relevant to post before posted, chaos. Now I see that you need also write? In this case you need to know how that RFID works, in my opinion generally some devices only send data after read TAG with proper address of device or need to be asked differently one by one for data. This pls explain due your documentation. Via this info you need prepare your logic. Also you have already said that you have correct data with PC but this important info is missing.

Hello,

ok but did you check RX LED on CP if flash when you test TAG? Is this system of reading? You don't need ask RFID device for data? Check that RX LED, this is first hint...

Update: you call FB2 also with that instance DB together? Only for sure...

Hello,

from your pictures (update) is clear that some commands need to be send to RFID device for first to obtain data from sensor. Look again to screenshot, there is Command GS and then RFID return data. Better info is in next window (Port monitor) where is clear what values need have request to have correct data from sensor. This is what I've asked you before, if RFID work as own sender or need poll it for data. In this case you can't be lucky only with RECV block, you need prepare for first commands and send them with SEND block. Your PC application shows this, it send and receive data as is needed.