Follow-up from "Draft:Board support dev"

The following discussion from !95 (closed) should be addressed:

• @emilio.corigliano started a discussion:

  @federico.mandelli Use the right function getAPBFrequency and check the settings influenced by this value.

  The value used till now was multiplied by 2 w.r.t. the real APB peripheral frequency; it was used the APB timers frequency. Check that the values computed after this are correct.