Invert marlin step signals (no replies)

Hello everyone. I am using marlin, with the board defined as #99 (custom setup?). I have made my own electronics, consisting of l297s,298s and a few other goodies. My problem is that marlin outputs a low signal on the step pins, pulsing high when it wants to step. The L297s require a high signal, pulsing low when stepping. Is there any way to invert outputs in marlin? I know in GRBL there was an invert mask, you could chose if each output was default high or low.

Thanks!