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From: Mark on 27 May 2010 18:40
Hello World!

I am using MATLAB to write data to an Arduino. In MATLAB, I use the function fwrite to send 10 x 512 bytes of data and transmit this via the Arduino with an NRF24L01 like this:

for i = 1:10
data = (vector containing 512 bytes of data)
fwrite(s,data)
end

However, this seems to fail, since only 25% of the data reaches the Arduino correctly. When I use the same Baud rate with the following code, it works properly:

for i = 1:5120
data = (1 byte of data)
fwrite(s,data)
end

Can anyone tell me why the first code fails? The problem must lie in the time between bytes, since the duration of sending 1 byte is always the same. Why should the time between bytes matter?
From: Walter Roberson on 27 May 2010 18:50
Mark wrote:

> I am using MATLAB to write data to an Arduino. In MATLAB, I use the
> function fwrite to send 10 x 512 bytes of data and transmit this via the
> Arduino with an NRF24L01 like this:
>
> for i = 1:10
> data = (vector containing 512 bytes of data)
> fwrite(s,data)
> end
>
> However, this seems to fail, since only 25% of the data reaches the
> Arduino correctly. When I use the same Baud rate with the following
> code, it works properly:
>
> for i = 1:5120
> data = (1 byte of data)
> fwrite(s,data)
> end

What is your flow control set to? Hardware flow control, one hopes.


> Can anyone tell me why the first code fails? The problem must lie in the
> time between bytes, since the duration of sending 1 byte is always the
> same. Why should the time between bytes matter?

The NRF24L01 appears to be a packet-oriented device, and is going to need time
to transmit each packet. The device has only a 32 byte RX and TX buffer.
http://www.nordicsemi.no/files/Prod_brief_RFSilicon_nRF24L01.pdf
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