Issue
160 November 2003
RF
Made Simple
DEAD-EASY
WIRELESS
Enough
theory already. If I’ve missed something, I’ll cover
it as I explain how to assemble easy-Radio hardware.
I have an easy-Radio evaluation kit and four easy-Radio
900-MHz hoppers. The radio boards that came with the
evaluation kit are shown in Photo 1. This is supposed
to be easy, so I’m not going to design and fabricate
any elaborate circuit boards or write any fancy microcontroller
firmware to make the easy-Radios work.
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(Click
here to enlarge)
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Photo
1—I used an unused in-line socket to mount the PIC12F675
data rate converter module. I took this photo before
I beefed up the voltage regulator on both of the
easy-Radio boards. I used the RS-232 port and the
services of RS-232 circuitry on an unrelated microcontroller-based
project board to feed the remote easy-Radio during
development and debugging. |
I
grabbed a couple of the easy-Radio hoppers and plugged
them into the evaluation kit radio boards. The evaluation
radio boards are simple and consist of an RS-232 converter
IC, a low-power 5-V regulator, configuration jumpers,
a couple of blocking diodes, a 9-V battery clip, an
in-line socket for the easy-Radio module, a wall-wart
jack, an antenna connector, and some LEDs. The easy-Radio
hoppers are nine-pin, in-line devices that are keyed
for foolproof insertion into the in-line socket on the
evaluation board.
Using
my laptop as point A and a PC as point B, I connected
the easy-Radios to the PCs with a standard nine-pin,
male-to-female cable. I invoked HyperTerminal on the
PCs, strapped a couple of 9-V batteries on the radio
evaluation boards, and fired them up. Everything worked
as I had planned. I was able to transmit and receive
on both PCs using the easy-Radio modules.
DEAD-EASY
E-MAIL
You
guessed it, the easy-Radios are going to join an easy-Radio
frequency-hopping network and send whatever data they
share as an e-mail. Again, there will be no intricate
custom PCBs or tricky software involved in the e-mail
process. I have a proper English friend, Trevor, who
uses the term “dead easy” quite often in our electronic
conversations. Because LPRS is a United Kingdom-based
company, I’m really surprised that LPRS didn’t call
this “Dead-Easy Radio” (grin).
My
web site ISP recently sold all of its dial-up accounts.
Because my e-mail package is rolled into my web site
contract, I used the dial-up account for Internet gadget
testing purposes. The new dial-up provider doubled the
price of my dial-up access, which prompted me to discontinue
my dial-up service. When I had finalized the idea for
this column, I went dial-up ISP shopping. I really don’t
need 199 mailboxes, spam relief, or high-speed access
and a web page. I simply want to dial up, hook up, and
transfer a few bytes of data between Internet widgets.
The cheapest local dial-up ISP wanted $12 per month
prepaid for one year. That’s pretty good, but I know
where I can get the data service I want for $2 per month
with a local phone number and an easy-to-use embedded
modem to boot.
What
you see in Photo 2 is the new and improved Cermetek
CH2124 mounted on an iModem evaluation board. This version
of the CH2124 sends and receives e-mail using the standard
PPP or CHAP authentication protocols. The circuitry
and algorithms within the new CH2124 have been updated
to provide faster and more reliable dial-up connections.
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(Click
here to enlarge)
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Photo
2—The iModem evaluation board is a great tool; it
saved me lots of time during the development phase
of this project. Everything you need to make the
modem go is on the iModem board. |
You
don’t need to be intimate with TCP/IP, SMTP, POP3, or
any of those nerdy protocols to use a CH2124; it is
a set-and-forget, stand-alone kind of communications
device. There are provisions for interfacing to an external
microcontroller, but you don’t need to add one, because
the CH2124 can store a canned e-mail message and send
it with the drop of a logic level. On the other hand,
you can get as nerdy as you wish. For instance, you
can acquire full control of the CH2124 modem and send/receive
process using your hardware, code, and favorite processor
or microcontroller.
Shortly
after my regular FedEx representative, Chris, delivered
my new CH2124, I plugged it into my iModem evaluation
board, attached a phone line, supplied some power via
a 9-VDC wall wart, and hit the Send button (see Photo
2). I spend an inordinate amount of time in front of
my all-in-one e-mail PC (it sits next to my production
and design monitors), and I like to answer e-mail messages
as quickly as I get them. So, I set the e-mail PC to
ask for e-mail messages every 60 s. I heard the iModem
evaluation board/CH2124 combination connect, and, less
than 1 min. later, I had an e-mail from the CH2124.
You’re
probably saying, “No way, Fred!” My initial e-mail from
the out-of-the-box CH2124 is shown in Photo 3.
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(Click
here to enlarge)
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Photo
3—The text you see in the original e-mail shot is
easily changed using the @TM1 command. Each remote
easy-Radio can send a custom message by using this
command followed by the microcontroller-generated
text message. |
I
told you this would be dead easy, didn’t I? All Cermetek
CH2124 iModems are customized and tested before delivery.
To put the CH2124 online in Stand-Alone mode and deliver
the message of my choice, all I have to do is connect
the iModem evaluation board to a PC running a terminal
emulator program, and then issue a simple @T iModem
command to change the canned message. Everything else
needed for sending an e-mail using the Cermetek $2 ISP
and the CH2124 was already loaded.
