Custom signal generation in AD-FMCDAQ2 (AD9144 DAC)

I am trying to generate a 400 MHz gaussian pulse using the AD-FMCDAQ2 with a pulse repetition frequency of 1KHz (every 1 ms). I used the following matlab code to generate the wave and store it in a .mat format.

fs = 2e9;
tc = gauspuls('cutoff',400e6,0.5,[],-5);
t = -tc:1/fs:tc;
x = gauspuls(t,400e6,0.5); 

ts = 0:1/2e9:0.001;
d = [0:1/1e3:0.001];
y = pulstran(ts,d,x,fs);

% xlim([0 0.1])
xlabel('Time (s)')

The variable y is transposed and save to a .mat file. 

However, when loading the .mat file to IIO, I get the error:

unable to create buffer due to sample size and number of samples

I would have uploaded the .MAT file as well, but I did not find a way to do that. It has 2000001 rows x1 column (double) and it's size is ~56kB.

Please advise.