User Manual

 2014 Microchip Technology Inc. DS50002325A-page 33
RN41/42 EVALUATION KIT
USER’S GUIDE
Chapter 3. Application Design Concerns
3.1 INTRODUCTION
The following sections provide information on designing with the RN41 and RN42 mod-
ules, including radio interference, factory reset, solder reflow profile, connection status,
and so on.
3.2 CONCERNS RELATED TO RN41/42
3.2.1 Reset Circuit
The RN41 contains a 1k pull-up to VCC, and the reset polarity is active-low. The mod-
ule’s reset pin has an optional power on-reset circuit with a delay, which must be only
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, the designers can use one of the many
low-cost power supervisor chips currently available, such as the MCP809 and
MCP102/121.
3.2.2 Factory Reset Using GPIO4
It is recommended that the designers 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 not properly
configured. To reset the module to the factory defaults, GPIO4 must be high on
power-up and then toggle the switch in an ON-OFF-ON-OFF-ON sequence with one
second interval between the transitions.
3.2.3 Connection Status
GPIO5 is available to drive an LED, and it blinks at various speeds to indicate status,
see Tabl e 3-1 . GPIO2 is an output that directly reflects the connection state as shown
in Tabl e 3-2 .
TABLE 3-1: GPIO5 STATUS
TABLE 3-2: GPIO2 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.
GPIO2 Status Description
High The module is connected to another device over Bluetooth.
Low The module is not connected over Bluetooth.