Mesa 7i76 invert PWM ?

I have a 6i25 7i76 setup that is outputting a PWM signal on an extra step generator (thank you peter). When my control box is powered on and linuxcnc is not running my PWM is at 5v. Is there a way to invert this signal so that I am getting 0v in that situation so i dont have to run it through a relay to cutoff output when linxcnc is not running?

Hope that made sense and here are my relevant hal lines.

# --- LASER POWER ---

setp hm2_5i25.0.7i76.0.0.output-00-invert true
setp hm2_5i25.0.7i76.0.0.output-01-invert true
net laser-shutter-output      => hm2_5i25.0.7i76.0.0.output-00
net laser-on-output        => hm2_5i25.0.7i76.0.0.output-01

setp   hm2_5i25.0.pwmgen.pwm_frequency 100
setp   hm2_5i25.0.pwmgen.00.scale 200
net laser-pwm-enable   => hm2_5i25.0.pwmgen.00.enable
net laser-pwm-value  <= motion.analog-out-00 => hm2_5i25.0.pwmgen.00.value

Thanks
Kent

 

Since you say 5V, assuming using the IDC26 connector, so inverting does not work for you, but using a single transistor and 2 resistors can do that easily.
Might also check the 7i76 manual if there is a possibility of disabling the pull up resistors, but even if it is, it would mean the outputs will be 3.3V, not 5V, usually not a problem.