AnsweredAssumed Answered

USB Virtual Com port

Question asked by Ken Su on May 11, 2017
Latest reply on May 11, 2017 by jeremyzhou



I have a problem with Virtual com port use.

I build the LPC1857 Virtual com port sample project, it work successfully.


But there is a problem with a procedure.


Step1: Power on 1857, and connect to PC with USB. PC will find a new com port.

Step2: Open Terminal Tool (I use TeraTerm), connect to this com port and start to receive/send data.

Step3: Re-connect USB line(also power RESET 1857), the terminal tool will not receive any data.

Step4: The terminal tool is still connected to this port, I close the terminal program.


Step5: Open terminal tool again, but it cannot find this com port. 


In Step5, I check the device manager, the com port is still exist. 


I think Step1 to Step4 is correct beahvior for common USB to Com device.


But Step5 is strange, I think the terminal should find the com port again.


Does it cause by firmware or driver? I think it's not terminal tool issue, because I check many common USB-UART port converter, they don't have this issue.