RF transceiver ideas

Started by Mohammed El Korek December 19, 2006
Hello everyone,

I am just beginning to look into the possibility of interfacing an RF
transceiver into a Minidragon+ board.. it's going to be my first time doing
it and I would just like to know if anyone had done this before ... i am
trying to see what are the applications you guyz have done using an RF
transceiver and a HC12-based platform.... any pitfalls, potential problems,
external circuitry... i have nt beginning working on it yet but i just need
some general responses/guidelines.......

thanks!!!

Mohammed El Korek
American University of Sharjah
"RF transceiver" is a bit vague description. There are quite a handful
of transceiver chips around which use SPI interface, those are pretty
much platform independent. There are RF modem chips as well which
interface with the UART directly or UART for data SPI for control.

You will find chips anywhere between 400MHz and 2.4GHz carrier and 4800
baud to over a megabit/s data speed, from a few metres of range to over
a kilometre.

Chips also vary how much of any particular protocol they realise in
silicon. There are chips that implement the entire 802.15 MAC layer,
others give you packet transfer with simple error detection and
possibly correction in hardware, down to the simplest modem with serial
in, serial out where packet formats, error handling and protocol are all
your responsibility.

Several manufacturers are around, Freescale being one, Chipcon was
recently bought up by TI, as far as I know Xemics was bought up by some
company maybe a year ago too - you shall look around. You will find
that there are several small manufacturers focusing on particular
niches of the RF market in Europe, mostly in Scandinavian countries and
Germany.

The external circuitry depends on the chip and your application. Most
modern chips require no more than a 6-10 passive component matching
circuit (although on 2.4GHz you can get away with PCB tracks as
matching circuit and antenna), however, if you want (and are allowed) to
boost output power most chips give you the signals to do so. Also, you
may fancy a SAW filter, which has its advantages and disadvantages. Some
chips require you to employ an external directional switch for the
antenna, alternatively (e.g. a Freescale 2.4GHz chip) suggests to use 2
antennas, which, apart from the PCB real estate are very cheap. Other
chips have the switch built-in and you don't have to bother, unless you
want an external amplifier, in which case you do.

Each chip has its own individual set of pitfalls and trickery, you have
to work out what you want to do first, then select a few contenders and
*then* ask the question about the specific chips on your shortlist.When
you get the responses, then you weigh the pros and cons for each and
choose the one with which you will get stuck and become and expert
of :-).

So, "RF transceiver", as I mentioned, is not a very specific
description. You have to narrow the field to get meaningful answers.

Regards,

Zoltan
Hello,

in the 2.4 GHz band, the TI CC2500 chip is very easy to work with --
it requires minimal external components, needs only one antenna which
can be printed on the pcb, and communicates with the MCU via SPI.

There is good sample code for various communication protocols on the
TI site:
http://focus.ti.com/docs/prod/folders/print/cc2500.html

The biggest challenge is soldering in the minuscule leg-less chips,
unless you buy one of the read EVBs.

The CC1100 does the same for the 300 to 928 MHz bands (longer range,
but requires larger antennas.

Best regards
Robert Imhoff
--- In 6..., "Mohammed El Korek"
wrote:
>
> Hello everyone,
>
> I am just beginning to look into the possibility of interfacing
> an RF transceiver into a Minidragon+ board.. it's going to be my
> first time doing it and I would just like to know if anyone had
> done this before ...

I use MaxStream modules, which gives a good range of selection for
price or power. I like them because they are good, solid (handling
error checking and other good features), and I don't have to know how
the RF part works.
http://www.maxstream.net/
Dear Mohammed El Korek.

You probably wonder why you may be so reluctant to interface you're
transceiver into a Minidragon+ board. I have never used the
minidragon+ board simply because of the price. If you would like to
start projects using an transceiver into a board you may like to
start off with something that is just as good, you will need to etch
you're own circuit boards, but that only adds up to be 23$ where the
minidragon is 120+ when it's new. you can buy a new transceiver
package from parallex.com for only 109. They will hook up to you're
computers serials with 3$ mod and that's good to go. bringing you're
total for the board and the transceiver's up to $132.00 which is just
a little bit more then the minidragon+ board, and since you buy more
then 100$ in product from parallax you may be eligible for free
shipping. however this is unknown shipping may go as high as $35
which is still lower then the cost of a minidragon and transceivers.

Projects you may want to look into would be "interactive applications"
where the user can control what ever it is you make.
A modem or control box for Sky Signs or Marquees can be programmed
remotely using a custom made user friendly application on any mac or
pc. I know people that make a living just making signs.
With a GPS device also added to you're project you can remotely track
and use your device Possibility's don't end very quickly. here are a
few more suggestions.

*indicates (already suggested)

Remote Usage. (control what's outside.)*
Remote Tracking (Find out where your application is)*
Remote data acquisition (read RFID's, Barcodes, environmental
variables, ect...)

Sorry I can not help you with the Minidragon+ board I do suggest that
you look into the propeller series micro computers from
www.parallax.com
--- In 6..., "x_t_a_n_g_e_n_t_3" wrote:
> You probably wonder why you may be so reluctant to interface you're
> transceiver into a Minidragon+ board. I have never used the
> minidragon+ board simply because of the price. If you would like to
> start projects using an transceiver into a board you may like to
> start off with something that is just as good, you will need to etch
> you're own circuit boards, but that only adds up to be 23$
> where the minidragon is 120+ when it's new.

Only $23 dollars, where do you find the time?? One of us is missing
something here.

> you can buy a new transceiver
> package from parallex.com for only 109.

"Sale Price: $129.95" is $20 off, but I don't see the 109. Who do you
work for, again?

[ noted wrong spelling of parallax, and found that "Parallex is
getting a brand new look!" ]

> They will hook up to you're
> computers serials with 3$ mod and that's good to go. bringing you're
> total for the board and the transceiver's up to $132.00 which is

Oh. Either you are not good with math, or the 109 was a typo.

> just a little bit more then the minidragon+ board, and since you buy
> more then 100$ in product from parallax you may be eligible for free
> shipping. however this is unknown shipping may go as high as $35
> which is still lower then the cost of a minidragon and transceivers.

Maybe you should include the link [http://evbplus.com/ ] for
reference. You will find many of us have got a much better deal than
$119 for the tiny "minidragon" series. Shoot, I got the full Dragon12
for $130 some time ago, and WELL worth it. I would compare it with
some near $400. Let me set it straight that I don't go for the price
jump, but I definitely recommended the Minidragon back when it was
near $50.

Note than a hobbyist or student still gets the Minidragon+ for $99,
and gives MUCH more capability than other manufacurer's board of same
price. The price increased because of the improved features. It can do
nearly everything the Dragon12 did (some differences are smaller size
and LCD is separate).

> Sorry I can not help you with the Minidragon+ board I do suggest
> that you look into the propeller series micro computers from
> www.parallax.com

I think you're missing the point of the question. When someone asks
how to add wireless to their Minidragon+, it does no good to try to
tell them to buy some other dev kit instead.

1. I'm pretty sure they've already got the Minidragon+. It won't save
money to buy yet another $100+ kit.

2. Mostly when someone mentions a decision like using Freescale 16-bit
MCU, that's a pretty big decision. They will not be prepared to run
off and re-learn everything to switch to some wierd thing called the
"Propeller".

3. What does Parallax even have to do with this group ?!

4. Looking at the Propeller, It just doesn't seem scalable, nor could
I choose a variation of the chip that costs less and only does what I
need for my project.

5. There's something fishy about Parallax. All the stuff is only good
for childs play, then suddenly they pop up this superduper "Propeller"
with 8 internal processors. What should I expect from it?

6. Sure the "Propeller" sounds neat, but I'll let YOU test it out
first, and see if it really is a big hit. Maybe if it becomes widely
used as HC11, then I'll consider changing. Otherwise, ARM7 sounds
great if I were planning to change over to something.

7. Wait a minute... I thought you were answering the question about an
RF hardware. I don't even see any RF hardware on the Propeller board,
in fact I don't see anything except maybe some LEDs. That's NOTHING
compared to the features on Minidragon+. Maybe the Propeller is good
for someone needing ultra processing power (more than RF interfacing
needs), but doesn't look good for anything else.