Connecting to USB device with serialport vs. serial command

I have a TrueRNG usb random number generator that I can connect to and read data from using the serial command. However, serial is being replaced by serialport but I am having difficulty reading from the device using the new configuration method. I am assuming I am making a mistake in how the communication settings are configured. Below are my steps for each method. I'd really appreciate any help in figuring out what I'm doing wrong with the serialport method.

I'm running Matlab R2022a.

Old Method which currenlty works got get data.

Device = ls('/dev/cu.usb*');
spaces = find(isspace(Device));
Device(spaces) = [];
RNGobj=serial(Device);
RNGobj.BaudRate=460800;
RNGobj.Terminator='CR';
RNGobj.ByteOrder='bigEndian';
RNGobj.InputBufferSize=2^18; 
RNGobj.BytesAvailableFcnMode='byte';
RNGobj.BytesAvailableFcnCount=2^10; 
fopen(RNGobj);
fread(RNGobj, 1, 'int8')
% Returns a random number. 
ans =  -79

This produces a random number (EX: -79)

New method using serialport which produces an error

% attempt to replicate the above with serialport 
Device = ls('/dev/cu.usb*');
spaces = find(isspace(Device));
Device(spaces) = [];
RNGobj=serialport(Device, 460800, "ByteOrder", "big-Endian");
configureTerminator(RNGobj,"CR");
RNGobj.InputBufferSize=2^18;
configureCallback(RNGobj,"byte",2^10,@BytesAvailableFcn)
fopen(RNGobj)
fread(RNGobj, 1, 'int8')
% Returns an empty value 
ans = [];

Running the above produces an empty value [] and the warning below:

Warning: The specified amount of data was not returned within the Timeout period for 'read'.

'serialport' unable to read any data. For more information on possible reasons, see serialport Read Warnings.

Answer 1

[Walter Roberson]

serialport does not have any fopen() or fread() . It automatically opens the port when you create the object, and it uses read() or readline()

Also I recommend that you use serialportlist instead of ls() like that.

Your read from the port should really be within the BytesAvailableFcn -- at which point it would be dealing with data already in the buffer.

In a case such as this where you are wanting to read bytes outside of the callback, you should probably not be configuring a callback.

[Daemonic]

Thank you Walter. So if I remove the configureCallback(RNGobj,"byte",2^10,@BytesAvailableFcn) line and use read(RNGobj, 1, 'int8') I come up against the same problem. Any adivce how to access the device without the callback function?

[Walter Roberson]

If you are doing a binary read of data, then you should not be configuring any terminator (not unless you have solid reason to expect that the binary data will never accidentally match the terminator -- for example the Kermit protocol promised that.)

After you have finished configuring the object, I suggest using flush() on the object. Then for debugging, please display the serialport object itself... and getpinstatus() of the object might also be interesting

[Daemonic]

Really appreciate your help, Walter.

Here's updated config:

Devices = serialportlist('available'); Device = Devices(contains(serialportlist('available'),'/dev/cu.usb'));
RNGobj=serialport(Device, 460800, "ByteOrder", "big-Endian");
RNGobj.InputBufferSize=2^18;
flush(RNGobj);
read(RNGobj);

Still produces the same error, unfortunately. Here is the object info

and the getpinstatus()

[Walter Roberson]

Interesting. I would suggest experimenting with setDTR

[Daemonic]

Thanks for the tip... unfortunately - no dice. I also tried connecting using the Instrument Toolbox which works great. Unfortunately, the toolbox utilizes the old method of creating a serial object.