Streaming data using serialport

Hi,

I am using serialport() object to hex data from a serial port. I can read a data section by setting the 'TimeOut' property of the serial object and setting the number for characters to read with the read() function. But I wish to read the data continuously, as long as the serial port is connected to the computer. The 'ReadAsyncMode’ mode does not work with serialport() object. Does anyone know how to read data continuously using the serialport() object? Thanks.

Answer 1

[Walter Roberson]

serialport() is continually reading and putting data into a buffer. As long as you do not overflow the buffer, it will grab data in the background.

In the situation you describe, you would typically use https://www.mathworks.com/help/matlab/ref/serialport.configurecallback.html configureCallback for "byte" and a count and a callback handle that is to be invoked each time sufficient data is read in.

[Rifat]

Ah, that makes sense! Thanks.

[Rifat]

Hi,

My MATLAB program can read and process the incoming data from the serial port. However, I am wondering if I am losing batches of data while still processing the previous batches. I do see some discrepancies in the ID number for the data batch, but not sure if the issue is due to data overflow in the buffer or the read-process operation itself. Note the data streaming rate is quite high, about 1Mbps.

Thanks.

[Walter Roberson]

@Rifat

Are you using the older (and now no longer recommended) serial or the newer serialport ?

serial() allowed buffer sizes to be changed, serialport() does not appear to have any method to configure buffer sizes.

[Rifat]

I am using serialport.

Do you mean serial() allowed configuring the buffer size of the PC's serial port? Does serialport comes with a fixed buffer size setting or it has no such property to control the buffer size?

Thanks.

[Walter Roberson]

The older serial() port had https://www.mathworks.com/help/matlab/ref/serial-properties.html#mw_5d33f1bd-97a2-4474-b2ea-8499775ddce4 -- InputBufferSize property (default: 512) and https://www.mathworks.com/help/matlab/ref/serial-properties.html#mw_f12b6a94-309a-4c7b-a160-f585876d0b35 -- OutputBufferSize (default: 512)

The newer serialport() has no documented buffer size control. In practice, though, it has hidden user-settable properties InputBufferSize and OutputBufferSize . With the properties not being documented, I cannot promise that it will actually use the buffer size that is set.

Historically, Mathworks has occasionally created object properties that they intend to implement in future, but hard-coding behaviour for a while, or keeping the properties hidden until they are finished testing or finished getting bugs out to their satisfaction. So the fact that the properties exist does not mean that they are used or that they function properly at this point.

... but you could try changing them and see what happens.

[Rifat]

Thanks Walter for a bit of a serialport()'s background. I will give it a go.