Main Content


(To be removed) Stop asynchronous read and write operations

This serial, Bluetooth, tcpip, udp, visa, and gpib object function will be removed in a future release. Use serialport, bluetooth, tcpclient, tcpserver, udpport, and visadev object functions instead. For more information, see Compatibility Considerations.





An interface object or an array of interface objects.


stopasync(obj) stops any asynchronous read or write operation that is in progress for obj.


You can write data asynchronously using the fprintf or fwrite functions. You can read data asynchronously using the readasync function, or by configuring the ReadAsyncMode property to continuous (serial port, TCPIP, UDP, and VISA-serial objects). In-progress asynchronous operations are indicated by the TransferStatus property.

If obj is an array of interface objects and one of the objects cannot be stopped, the remaining objects in the array are stopped and a warning is returned. After an object stops,

  • Its TransferStatus property is configured to idle.

  • Its ReadAsyncMode property is configured to manual (serial port, TCPIP, UDP, and VISA-serial objects).

  • The data in its output buffer is flushed.

Data in the input buffer is not flushed. You can return this data to the MATLAB® workspace using any of the synchronous read functions. If you execute the readasync function, or configure the ReadAsyncMode property to continuous, then the new data is appended to the existing data in the input buffer.

Compatibility Considerations

expand all

Not recommended starting in R2019b

Not recommended starting in R2020b

Not recommended starting in R2020b

Not recommended starting in R2020b

Not recommended starting in R2021a

Not recommended starting in R2021b

See Also



Introduced before R2006a