BOO if you soldered the two wires, and it just works like another trigger (single fire) then you either A have fully charged batteries and the PWM is firing too fast for the controller to recognise, or B you are not modding a matrix controller.
But seriously once you take the step into microcontrollers to preform the rapid fire you will be much better off as laxboy stated and provided a link to we have alot of freeware codes to choose from on this site.