RN42 Datasheet, PDF (7/26 Pages) Microchip Technology – Class 2 Bluetooth® Module with EDR Support

2.0 APPLICATION INFORMATION
The following sections provide information on design-
ing with the RN42/RN42N module, including radio
interference, factory reset, solder reflow profile, con-
nection status, and so on.
2.1 Reset Circuit
The RN42/RN42N contains a weak internal pull-up to
VCC, and the reset polarity is active low. The module’s
reset pin has an optional Power-on Reset circuit with a
delay, which should only be required if the input power
supply has a very slow ramp or tends to bounce or have
instability on power-up. Often a microcontroller or
embedded CPU I/O is available to generate the reset
once power is stable. If not, designers can use one of
the many low-cost power supervisor chips available,
such as the MCP809 or MCP102/121.
2.2 Factory Reset Using GPIO4
It is recommended to connect the GPIO4 pin to a
switch, jumper, or resistor so it can be accessed. This
pin can be used to reset the module to its factory
default settings, which is critical in situations where the
module has been misconfigure d. To reset the module
to the factory defaults, GPIO4 should be high on
power-up and then toggle between low and high twice
with a 1 second wait between the low-high transitions.
2.3 Connection Status
GPIO5 is available to drive an LED, and it blinks at var-
ious speeds to indicate status, see Table 2-1. GPIO2 is
an output that directly reflects the connection state as
shown in Table 2-2.
TABLE 2-1: GPIO5 STATUS
GPIO5 Status
Description
Toggle at 1 Hz
Toggle at 10 Hz
High
The module is discoverable and
waiting for a connection.
The module is in command mode.
The module is connected to
another device over Bluetooth.
TABLE 2-2: GPIO2 STATUS
GPIO2 Status
Description
High
Low
The module is connected to
another device over Bluetooth.
The module is not connected over
Bluetooth.
RN42/RN42N
2.4 Module Mounting Details
Figure 2-1 and Figure 2-2 show the recommended
PCB footprint for the RN42 and RN42N, respectively.
When laying out the carrier board for the RN42 module,
the areas under the antenna and shielding connections
should not have surface traces, ground planes, or
exposed vias.
Figure 2-3 and Figure 2-4 show the recommended
mounting details for the RN42 and RN42N, respec-
tively. For optimal radio performance, the RN42 mod-
ule’s antenna end should protrude at least 31 mm
beyond any metal enclosure.
Figure 2-5 shows examples of good, bad, and accept-
able positioning of the RN42/RN42N on the host PCB.
FIGURE 2-1:
RN42 RECOMMENDED
PCB FOOTPRINT
Top View
25.8
20.5
19.7
16.0
14.8
13.6
12.4
11.2
10.0
8.8
7.6
6.4
5.2
4.0
2.8
0.7
0.0
Dimensions are in millimeters
0.70mm
2.00mm
0.80mm
Shield Pads
4 Corners
1.0 x 1.8mm
Do not locate
vias or surface
traces under
Shield Pads
 2015 Microchip Technology Inc.
DS50002328A-page 7