What is the Arduino Simulink BLE data transmission frequency using matlab block and ble() function

Hello!

I am using Matlab block in Matlab Simulink to connect, send and receive data between my laptop and 3 Arduino Nano BLE devices.

Within the matlab block I use:

1. blelist and ble('devicename') to search and connect to the device
2. Characteristic(device name,"ServiceUUID", "CharacteristicUUID")
3. Convert the received data from Byte format to double double(typecast(uint8(read(Received data structure)), 'uint32'))

The connection works well and is stable etc. however when I plot the data I can only get it to receive data every 3 seconds.

I already tried to change the simulink time step settings etc without success.

My question: How can I receive data at a higher frequency? Am I making any obvious error?

Many thanks in advance

[Walter Roberson]

https://en.m.wikipedia.org/wiki/Bluetooth_Low_Energy

At least 1 megabit per second basic rate.

Which does not answer your question about why you have that delay.

When you are in the plotting loop are you recreating the connection for every data point, or reading multiple points from each session?

[Marvin Wright]

Hi Walter,

Thank you for your reply!

Its the same session, below is the general code structure:

%If not connected, scan and connect to device
%I do this with 3 Arduinos, so the below code x 4
if isempty(b1)
    blelist;
    b1 = ble("Device name")         
end
      
%set characteristic
%I share 9 Characteristic between laptop and Arduino, all in the same
%Service for simplicity, all BLEIntCharacteristic type on the Arduino
%So in total 27 Characteristics.

Data1 = characteristic(b1,"ServiceUUID", "CharUUID1");
...      
Data9 = characteristic(b1,"ServiceUUID", "CharUUID9");

%Out of the 9 Charachteristics 6 are control variables I change via laptop
%Can be assumed constant as I dont change them often
write(Data1, 'variable')
...
write(Data7, 'variable')    

%the remaining 3 Chars I am reading
%These variables I would like to receive at a higher frequency
double(typecast(uint8(read(Data7)), 'uint32'))
...
double(typecast(uint8(read(Data9)), 'uint32')) 

[Walter Roberson]

But you do not show any loop there. Are you creating the ble connection once, either in an InitFcn callback or in the model initialization stage and storing it in a persistent variable? Or are you creating the connection and tearing it down every time the MATLAB Function Block fires?

[Marvin Wright]

Yes, I currently dont use a loop. In my understanding the Simulink model would continously loop through the matlab block. Also, yes I am using persistent variables within the Matlab block.

So I should run a loop within the matlab block? while(1) ?

Thank you

[Walter Roberson]

You should move the setting of characteristics to inside the if isempty() . Outside of the isempty() should be reserved for making changes to setting or reading or writing from the device.

If you need to read an indefinite number of times after each write (perhaps the writes are triggered or due to user input), then you should split the function into a read function and a write function. In that situation you would probably convert from persistent variable to global variable in a Data Store, and probably use an initFcn() callback to trigger initialization of the ble object.