SCREENSHOT 1. This Tera Term Pro capture lists everything
we can do with the MRF24J40 Radio Utility Driver. It looks like
this could be fun even without having to put on a pointy
SCREENSHOT 2. There are some really interesting menu
options here, as well. However, our goal is to send and receive
some data. So, I figure we won’t be configuring any external
PAs or LNAs today.
SCREENSHOT 3. As you can see in this capture, the lowest
power output we can dial in is between 0.001 and 0.0001
milliwatts. The MRF24J40MA is able to track a signal with a
single strength as low as -94 dBm. The MRF24J40MA’s receiver
overloads at anything above + 5 dBm.
PHOTO 6. If you really want to get serious with Mi Wi
or ZigBee, you need one of these.
board with a second module.
I’ve downloaded the MRF24J40 radio utility driver
which we’ll use to initially expose the capabilities of the
module. The radio utility driver will allow us to configure
the MRF24J40MA and run basic transmission and reception
tests. The radio utility driver package comes as a collection
of MPLAB projects with precompiled hex files. So, we only
need to program the PICDEM Z hex file into each of the
PICDEM Z/MRF24J40MA board pairs. After I set up a Tera
Term Pro session for 19200 bps, eight data bits, no parity,
and one Stop bit for each node, we should be ready to rock
and roll. According to the utility driver user information, we
should be welcomed by a Main Menu by way of the
PIC18LF4620’s RS-232 port and Tera Term Pro. Behold
What moves you in Screenshot 1 Personally, I really
want to jump to the Ping Pong Test, but I think we oughta
start by punching in “a.” Okay, “a” it is. Here we go again.
What moves you in Screenshot 2 I like “b.” Recall that the
MRF24J40MA datasheet specified a typical range of 400
feet. Well, now we know how far 1.0 milliwatts (+0 dBm)
off transmit power will take us. I chose to keep the output
power at +0 dBm.
I messed around with the other MRF24J40 radio utility
driver menu options and finally broke down and ran the
Ping Pong Test. As you can see in Screenshot 4, there’s
nothing new to report. The radio utility driver is definitely
aimed at the RF engineers that wear those funny hats. Let’s
go to Las Vegas.
Elvis Did It MiWi
Mi Wi is a Microchip protocol that can be used in very
simple wireless 802.15.4 networks. Our Mi Wi network will
consist of a Mi Wi Coordinator and a Mi Wi End Device with
both nodes configured as shown in Photo 5. The Mi Wi
package is a free download from the Microchip website and
comes with ready-to-run code for a PAN Coordinator and
End Device. I’ve loaded up the PICDEM Z hosts. So, let’s get
the PAN hot.
Here’s the plan. I’ll start up the Mi Wi Coordinator first.
It will search for a pre-existing network. Naturally, it won’t
find one and it will start a network of its own. Next, I’ll fire
52 SERVO 04.2010
PICDEM Z Demonstration Kit
Mi Wi Stack
MRF24J40MA IEEE 802.15.4 2. 4
MRF24J40 Radio Utility Driver