I've been thinking about how to set up the new H-bridge for the bell ringer.

We need 2 SPWM signals with dead-time inserted, going to try to use PIO to do this. My power supply gives out 40 volts, the H-Bridge IC datasheet mentions explicitly that going over 44 volt even for a brief time is not allowed. I have to make sure that the H-bridge IC does not receive back EMF from the coil exceeding 44 volts. 

I'm pretty sure that the ringer inductor have minimal back emf but I'm going to add a resistor over the coil anyway to be sure. I think I need to add a filter to remove pwm noise from the sinewave too.