RN42APL datasheet(7/26 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS50002328A-page 7

RN42/RN42N

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.

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

TABLE 2-1:

GPIO5 STATUS

GPIO5 Status

Description

Toggle at 1 Hz

The module is discoverable and

waiting for a connection.

Toggle at 10 Hz The module is in command mode.

High

The module is connected to

another device over Bluetooth.

TABLE 2-2:

GPIO2 STATUS

GPIO2 Status

Description

High

The module is connected to

another device over Bluetooth.

Low

The module is not connected over

Bluetooth.

0.70mm

0.80mm

2.00mm

0.0

0.7

2.8

4.0

5.2

6.4

7.6

8.8

10.0

11.2

12.4

13.6

14.8

16.0

25.8

19.7

Shield Pads

4 Corners

1.0 x 1.8mm

20.5

Do not locate

vias or surface

traces under

Shield Pads

Top View

Dimensions are in millimeters

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