User's Manual

www.rovingnetworks.com Version 3.43 5/21/13 page 8
RN41-DS
FIGURE 2-5: RN-41 HOST PCB EXAMPLE LAYOUT
2.6 External Antenna Types (RN-41N)
The RN-41N module’s antenna pin (pin 25) provides a
50-ohm impedance to external antennas. Pin 25 can
connect directly to a coaxial cable antenna or to an
antenna connector such as a U.FL or reverse polarity
SMA.
The PCB trace from pin 25 to the coaxial cable or con-
nector should be less than 0.2 inches (5 mm) for mini-
mum loss and the best impedance match. If the PCB
trace is longer, it should be a 50-ohm impedance
microstrip trace. Connect adjacent ground pins 24 and
26 to a low-impedance ground on the host PCB and the
antenna connection. Figure 2-4 gives example host
PCB layout to a U.FL connector.
Modular certification of the RN171 module was per-
formed with the external antenna types listed in
Table 2-3. Refer to Section 3.0, Regulatory Approval
for specific regulatory requirements by country.
2.7 HCI Mode
Roving Networks offers the Host Controller Interface
(HCI) mode in addition to the standard operational
mode of its Bluetooth modules (standard mode refers
to the on-board stack running on the module).
In HCI mode, the on-board stack is bypassed and the
module is put in a state that runs the Bluetooth base-
band. The HCI provides a command reference inter-
face to the baseband controller and the link manager,
and provides access to the hardware status and control
registers. This interface provides a uniform method for
accessing the Bluetooth baseband capabilities.
In this mode, the Bluetooth stack is no longer on-board
the module. It is offloaded to the interfacing host pro-
cessor. The Bluetooth module is used as a radio, per-
forming the lower level MAC functionalities, while the
application stack runs on the host processor.
Using the module in HCI mode allows designers to
implement profiles that are not natively supported on
the Bluetooth module.
No Copper
In these Areas
RN-41
Okay
RN-41
Best
RN-41
Okay
RN-41
Okay
TABLE 2-3: TESTED EXTERNAL
ANTENNA TYPES
Type Gain (dBi)
Monopole 0.56
Dipole 8
Yagi 15
Note: HCI mode requires a separate firmware
build that must be loaded into the mod-
ule’s flash at the factory. Is not upgrade-
able in the field.