Hi all, have been trying to add a small co2 laser tube using the same PWM signal on the remapped pin 44 which we have been successfully using a 2w diode laser, however the laser tube power supply which controls the laser seems to also need an active low signal (≤0.3V Laser On) to start the laser in addition to the PWM signal.
Would be grateful for any suggestions which pin we could use for this and/or how to allocate such a pin in firmware should it be necessary.
Well… on most boards the fan pin signal is only controlling the negative pin. So in theory… you could use any positive voltage pin you want. So if you can find a positive voltage pin with the voltage you need the. Just use the negative fan pin to control the on off signal it should work. That is how I am running right now. Some random 5 volt positive pin and the negative from the fan pin. In your situation you might need some kind of voltage divider to bring the positive voltage down to what you need. It’s an idea. Hope it helps.
Many thanks for that… we gave it a try with a 10k voltage divider for the laser on signal using the same pin 44 and it seems to work… 
Many thanks again…
Be careful! On the rambo boards, there is a little LED that brings the negative terminal up to 12V when the transistor is off.