Re: Choice of frequency and protocol on RF links?


Thanks Vladimir.

I also forgot to mention that the link needs to be secure..... I
wonder, does this eliminate the 433MHz option?!?



Vladimir Vassilevsky wrote:
ElderUberGeek wrote:

I am designing an RF link that is supposed to operate between an
embedded unit and a central control/collection unit (i.e. a PC with the
link hardware attached). The purpose of the link is to pass some data
(in form of strings), and then some control/session parameters.

The key questions are if the worldwide acceptance is required and if you
are willing to apply for approvals yourself.
If your quantities are small, then the best way would be using
pre-approved 2.4GHz modules like MaxStream or Cirronet. If you are
looking for the mass product, then it could make sense to do the RF part
yourself.

Here
are
the main features:
- Relatively low data speeds required

How much is "low"?

- Range of up to 20-30 meters (LOS, but occasional obstructions are
likely)

Should not be a problem.

- Needs to handle multiple devices (i.e. units) in same environment
(i.e. hitting the same controller)

Usually, this is the upper protocol issue.

The RF link component/module will interface with some MC in the
embedded module.

I am wondering what choice of frequency and protocol to select:
- 433 MHz (good old AM/FM??!)

Very cheap and simple, however not universally accepted.

- 2.4GHz WiFi (802.11)

Overkill.

- 2.4GHz Zigbee

May be a good solution. However it is not very cheap and not very simple
either. Same comments apply to BlueTooth.

Main considerations are:
- Cost of component/module
- Ease of design/integration

I am aware that all the above options can and do work, but am looking
for the best fit vis-a-vis the above main criteria.


Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

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