Read BLE and handle data in microsec level with MATLAB appdesigner

I want to read data from BLE(function in MATLAB) and handle the data.

BLE data is always 240 bytes(uint8), and the period is 1 ~ 6 msec level.

Every functions are defined and used in appdesigner GUI.

My problem is,

BLE data will store in memory ring buffer,(1 x 1,000,000)

and My data handler function will read data from buffer, and split by packets with head/tail identifier.

Data handler function is the callback function of timer which period is 1 msec.

I'm understanding the MATLAB's callback queue line is single.

When data handler execution time is longer than BLE data period,

the speed at which data is accumulated is faster than the speed at which data handled.

Is there any possible way to control two callback function in MATLAB?

or split the different size of packets with head/tail in (1 x 1,000,000) in very short time? (like ~ 100 microsec.)

BLE data example below :

BLE_DATA = [ head, data(124), tail, head, data(1), tail, head, data(,,,), tail ... ] %% size will (1 x 240),

%% but the head or tail will not always on the first / last location of array.

%% packet = [ head, data(124), tail] / [head, data(1), tail] ....

Every arrays in my codes are preallocated,

and the time I measured with "timeit", "tic / toc" during handle the 240 bytes at handler function is 400 ~ 600 us, including refreshing plot.

I tried to store BLE data in external file(csv, txt, xls), but the time for save / load the file is much longer than memory buffer.

Maybe my code was inefficient.

The data in packets should be save in external file, but this is also time-hunger process in MATLAB. (msec level)

I'm using MATLAB 2020b.

Any ideas or advice are welcome.

Thank you.

Answer 1

[Rasmita]

Hi,

It is my understanding that, you are trying to read data from ‘BLE’ function in MATLAB and handle the data. Also, you want to split the different size of 'BLE' packets with head/tail and store the data packets in an external file in very short time.

To handle the ‘BLE’ data in MATLAB, you can use the ‘ble’ object available in MATLAB. The ‘ble’ object provides the capability to scan and discover nearby ‘BLE’ devices, connect and disconnect from devices, and read and write data to devices. You can use the read method of the 'ble' object to read data from the device.

To handle the data received from the ‘BLE’ device, you can use a ‘timer’ object in MATLAB. You can set the ‘timer’ object to fire every 1 millisecond and call the ‘data handler’ function. In the ‘data handler’ function, you can read the data from the ring buffer and split it into packets using the ‘head/tail’ identifier.

To handle the case where the data handler function takes longer than the 'BLE' data period, you can use a separate thread to handle the 'BLE' data. MATLAB supports parallel computing using the ‘Parallel Computing Toolbox’. You can use the ‘parfeval’ function to execute the data handler function in a separate thread. The ‘parfeval’ function returns a ‘Future’ object, which you can use to check the status of the execution and get the results.

To split the packets in the ring buffer quickly, you can use the ‘strfind’ function to search for the ‘head/tail’ identifier in the ring buffer. The ‘strfind’ function returns the indices of the ‘head/tail’ identifier in the buffer, which you can use to split the buffer into packets.

For more information, please refer to the below documentation links:

https://www.mathworks.com/help/matlab/ref/ble.html

https://www.mathworks.com/help/matlab/ref/timer.html

https://www.mathworks.com/help/matlab/ref/parfeval.html

https://www.mathworks.com/help/matlab/ref/strfind.html

Hope this helps!

Regards,

Rasmita