code: def set_ard_time(self, us):
          
          # Auto Retransmit Delay:
          # 0000 - Wait 250uS
          # 0001 - Wait 500uS
          # 0010 - Wait 750uS
          # ........
          # 1111 - Wait 4000uS
  
          # Round down, to value representing a multiple of 250uS
          t = int((us / 250) - 1)
          if (t < 0):
              t = 0
          if (t > 0xF):
              t = 0xF
          _send_vendor_setup(self.handle, SET_RADIO_ARD, t, 0, ())
docs: Set the ACK retry delay for radio communication