User's Manual

DS-RN24_V2 1/28/2009
809 University Avenue • Los Gatos, CA 95032 • Tel [phone] • [e-mail]
Design Concerns
1. Reset circuit. RN-24 contains a 1k pulldown, the polarity of reset is ACTIVE HIGH.
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
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.
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. RS485 support. RS-485 signaling with auto-direction control is ONLY supported on PCB rev 4 and later. Treat
pins 22 and 23 as no connect on previous PCB boards.
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 integrating the RN24 DIP module with on board chip antenna be sure
the area around the chip antenna end of RN24-S module protrudes at least 5mm from the PCB and any metal
enclosure. If this is not possible use the RN24-E.
7. Soldering Reflow Profile.
• Lead-Free Solder Reflow
• Temp: 230 degree C , 30-40 seconds, Peak 250 degree C maximum.
• Preheat temp: 165 +- 15 degree C, 90 to 120 seconds.
• Time: Single Pass, One Time
8. Connecting to the GPIO. Placing 3.3Vdc into the PIO’s while they are set as outputs will permanently damage
the radio. The failure mode is short across GND and VCC. Use a 10KO resistor is series or a 10KO pull up
resistor for input and output PIO’s respectively.
• Make sure to connect a common ground when using the external TX, RX inputs on the 0 – 3.3Vdc
• For a 3 wire DB-9 interface (tx, rx, gnd only) connect/short CTS to RTS, Factory default is hardware flow
control enabled CTS and RTS connected.
• When using a 5.0Vdc Input, PIO’s require a 10K ohm series resistor. PIO’s are 0-3.3Vdc not 5 volt tolerant.
Compliance Information
• FCC Certified, FCC ID T9J-RN24, IC number6514A-RN24
• Environmentally friendly RoHS compliant
Ordering Information
Part Number Description
RN-24-S With chip antenna
RN-24-E With SMA jack
RN-25-S RS485 signaling with chip antenna
RN-25-E RS485 signaling with SMA jack