Slow stepper motor

Hello,, I am trying to send data directly from firefly mega write to a stepper motor with the firefly firmata.. I got the sequence of pulses that need to be sent.. problem is that it is not being sent fast enough.. I have a 1 ms timer rotating controlling the pulses, but it doesn't change anything..

The question is,, how to send the data fast enough (in 1ms intervals)to the arduino.. as far as I understand,, the grasshopper definition is working, but that might have something to do with the firmata or !!!!

Thanks all