Mathlab can not write data to serial port suddenly!

Hello I use Mathlab to send data via to microcontroller. I done this already. But just yesterday, Mathlab can not send to serial port suddenly. I don't know this why? I didn't change the code. Everything is correct. No error, no warning. I checked serial port information: serial-COM1 Status: open Baudrate: 9600 Terminator: CR/LF I use "fwrite" and "fprintf" function to send to microcontroller.In Mathlab, no error, the ValueSent is also increasing but device can not receive the data. Note that I used Terminal to send to microcontroller. It work fine. Please explane to me

Answer 1

[David Sanchez]

You may have created the serial object and are actually sending the signal to it, that is why no errors are returned. Make sure the COM number assigned to your devices has not changed.

[Duong Tu]

Yes! the COM number assigned to my device has not change. I use Terminal GUI for sending data. It work fine. Same condition, Terminal work fine but Mathlab is not

[David Sanchez]

Are you sure not other application holds the serial port?

[Duong Tu]

I am sure that others application don't hold the serial port. Because I use "instrfindall" to check available ports. If any application hold the serial port, Mathlab will not creat serial object which use that port.