You could try to use the same crystal to drive the uprocessor, assuming that you used the timer of the uprocessor,but then you would then have to deal with the slowness of execution speed of the uprocessor, because it is driven from such a slow clock.

That would be very feasible if a processor such as (some?) SILabs derivatives that have a PLL clock mmultipler was used. That would eliminate "have to deal with the slowness of execution speed"

Erik