Data Sheet

DS-RN41-V3.1 6/27/2011
809 University Avenue • Los Gatos, CA 95032 • Tel [phone] • [e-mail]
Design Concerns
1. Reset circuit. RN-41 contains a 1k pullup to VCC, the polarity of reset on the RN41 is ACTIVE LOW.
A power on reset circuit with delay is OPTIONAL on the reset pin of the module. It 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 IO is available to generate reset once power is stable. If not, there
are many low cost power supervisor chips available, such as MCP809, MCP102/121, and Torex XC61F.
2. Factory reset PIO4. It is a good idea to connect this pin to a switch, or jumper, or resistor, so it can be
accessed. This pin can be used to reset the module to FACTORY DEFAULTS and is often critical in
situations where the module has been mis-configured. To set Factory defaults start HIGH, then toggle
times.
3. Connection status. PIO5 is available to drive an LED, and blinks at various speeds to indicate status.
PIO2 is an output which directly reflects the connection state, it goes HIGH when connected, and LOW
otherwise.
4. HCI mode. The RN41 module must be loaded with special firmware to run in HCI mode. When in HCI
mode the standard SPP/DUN applications are disabled.
5. Using SPI bus for flash upgrade. While not required, this bus is very useful for configuring advanced
parameters of the Bluetooth modules, and is required for upgrading the firmware on modules. The
suggested ref-design shows a 6pin header which can be implemented to gain access to this bus. A
minimum-mode version could just use the SPI signals (4pins) and pickup ground and VCC from elsewhere
on the design.
6. Minimizing Radio interference. When laying out the carrier board for the RN41 module the areas under
the antenna and shielding connections should not have surface traces, GND planes, or exposed vias.
(See diagram to right) For optimal radio performance the antenna end of RN41 module should protrude
5mm past any metal enclosure.