I am testing out the fragment feature in a local app that communicates with a serial RS232 device. The thing is that commands and queries need to happen in a well defined sequence. The st.fragment function queries the device for status variables by first sending a command to the serial port and then reading the result. This part alone works well. A problem may arise when I start changing parameters from my apps UI in addition. Either it works or I get an error indicating multiple port access:
Serial.serialutil.SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?)
I tried to add a simple ‘lock’ state variable to sessionstate to prevent the access of the fragment function while I change parameters, but it didnt work.
Is there an easy fix for that like some asyncio thread lock function to prevent concurrent access to the serial port?