dc motor , monster moto shield VNH2SP30, Matlab

Hi

I want to control a dc motor with monster moto shield vnh2sp30 ,arduino uno and matlab as the datasheet of the shield the digital pins 7 and 8 are used to run the dc motor and the code that I have written is:

a=arduino('com9','uno');

writeDigitalPin(a,'D7',1);

writeDigitalPin(a,'D8',0);

but nothing happened