SPI with Arduino to control LEDs

Hello, I'm trying to control these APA102C LED's via SPI through an Arduino Due. You will see the SPI protocol if you scroll down.

a = arduino('COM6', 'DUE', 'Libraries', 'SPI');
LED = spidev(a, 'D11');

and

writeRead(LED, [0 0 0 0 255 0 0 255 0], 'uint8')

yields no results. I'm following this example. Is there anything wrong that you see? I'm on Matlab 2017a.

Thank you

[XecutionStyle]

I managed to get the SPI protocol working but I've run into a new issue. When trying to control many LED's I get this error: "SPI count for read and write operations have a limit of 144 for a data precision of 'uint8" and as a result can only control up to 28 LEDs. What is this cap and is there a way to increase it? If not, what alternative do I have to control up to 3-400 LED's?

Thanks in advance

[Madhu Govindarajan]

Have you tried using the Simulink support package for Arduino? That might eliminate the I/O issue you could be facing here.