■ SCHEMATIC 2. The RN-XV RTS and
CTS pins are in opposite positions of the
802.15.4 radio. You can either swap the
connections or eliminate them.
and receive pins are concerned. The
modification involved disabling the
original carrier’s RSSI circuitry. My
modified RN-XV carrier can be seen
in Photo 3.
Schematic 1 shows us that the
802.15.4 radio module’s pin 6 is the
radio’s RSSI output pin. The RN-XV
does not have an RSSI pin in this
position. Instead, pin 6 of the RN-XV
is GPIO5. Removing resistor R7 will
free GPIO5 and isolate the original
RSSI circuitry. The second part of the
modification involves the RTS and
CTS pins.
ROUTER SETUP
■ PHOTO 4. This is an old
Rabbit 802.15.4 radio
cradle. I verified that the
voltage regulator was still
working and plugged the
RN-XV into the socket. No
modifications were made
to the cradle.
My Linksys router has dynamic
DNS capability. When used in
conjunction with a DynDNS account,
I can (at any time) simply enter a
preset host name to find my router
and the RN-XV it supports via an
Internet connection. Within my
DynDNS account, I’ve set up a host
name of
nutsvolts.dyndns-server.com,
which we will use to contact the RN-XV you see sitting in yet another
802.15.4 radio cradle in Photo 4.
I re-enlisted this 802.15.4 radio
carrier because it supplies the
needed 3. 3 volt power rail and
provides easy access to the RN-XV’s
transmit and receive pins. The
pushbuttons, LEDs, and RS-232
interface IC are still on the cradle
because they aren’t hindering the
RN-XV’s operation.
The DynDNS feature of the
Linksys router allows us to associate
the host name I created with the
router. The next step involves
creating and opening a port on the
router. To keep things simple, we’ll
assign a port number of 8888 and
link it to an IP address of
192.168.0.88. I activated port 8888
16
February 2013
