Ultra low power short range RF

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I need to find RF components for a battery-powered (slave)
device that needs to do wireless communication. The master
device is not battery-powered and may consume more power.

My preliminary specs for slave are:
-continuous average current consumption <100uA
-communication speed is not an issue
-wakeup time for slave when master sends enquiry <50 ms
-data is not received/sent very often (couple of small packets/minute max)
 so current consumption while doing RX/TX is not that critical
-communication range VERY short (max AND min about 2-3 meters)

I'm more or less tied (mentally) with AVR, so I'm looking for
a companion for AVR controller.

I have found couple of options, one of them being Xemics XE1209.
Anyone has experienced a design with this one?

ANY ideas are welcome.

    Pygmi



Re: Ultra low power short range RF
look at AT86RF401, it is a transmitter with an AVR in the same chip


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Re: Ultra low power short range RF
Yes, it i sinteresting, but I just noticed that I forgot to clearly state
communication needs to by two-way...so I'll need transceivers.

The AT86RF211 on the other hand might be a choice...just need to
check the wakeup functionality.

Xemics XE1209 for example can be set to "partilly sleeping", woken by
carrier detection.
Another on might be transceivers that have built-in sleep cycles.
The <50 ms wakeup might however be a problem.

Pygmi

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Re: Ultra low power short range RF
One more thing...
What is the situation with this "Zigbee" standard.
Chips/products available?

    Pygmi

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Re: Ultra low power short range RF
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Zigbee is still in development, however the underlying RF standard
IEEE 802.15.4 is complete.

CompXs (http://www.compxs.com ) are selling development systems.

Cheers,
JonB

Re: Ultra low power short range RF

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Ok, thanks. Sort of got that impression, but wasn't sure...
Maybe some time in the near future.

   Pygmi



Re: Ultra low power short range RF

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Nordic VLSI nRF2401 (1uA sleep, 18mA while active)
http://www.nvlsi.no
If you want to take advantage of the version with integrated micro
controller (nRF24E1 not an AVR though;-) you will have a single chip
solution that runs off 1.9V - 3.6V (directly from 2 AAA or AA;-)
Both are easy to use  as they have most of the RF "tidbits" integrated.

With the power budget you have I would rather look into redefining the
master/slave functionality:
The mains powered unit default is receive mode, the battery powered unit
sends a message either every (x)seconds or when a change in status appear.
The battery powered unit then awaits an acknowledge within a set time
window, if noACK  received, it will retransmit.
With an ACK it will know that message transaction is complete and go back
into sleep.

If the Master is to "wake up" the batterypower unit, this unit must be in a
mode where the receiver will be able to detect that the master wants to
talk, (more than your 100uA).You will need a fairly accurate RTC (or
similar) for a power effective "time mulitiplexing" system.

HTH

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Morten
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Re: Ultra low power short range RF
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A local company is doing something similar for asset tracking - they've
got a PIC-based keyfob module that'll transmit for >5 years on a single
coin cell.  Wakes up every minute or so.

Re: Ultra low power short range RF
Hi,

Interesting chips, although not what I'm looking for right now.
I couldn't find how they would wakeup by themselves from
RF-signal.
And yes, unfortunately the master really needs to wake up the slave.
This is possible at least with
-Xemics XE1209 having mode where it is woke up by carrier
  (takes few ms)
-one Aurel transceiver, having RX current < 100 uA!
So I really need the RF to wake up the system, one way or another.
This means the uC too, so that I can keep it sleeping.

AND I forgot something from my first "spec"
It is not just:
"wakeup time for slave when master sends enquiry <50 ms"
It is really wakeup, RX (few bytes), RX-TX round delay and
TX (few bytes)
And hopefully decent TX-RX turn around delay as well....

Any timed solution is NOT possible, as the devices are not
on fixed position. RFID-kind of hardware would do the trick, but
the price tag for those devices is way beyond reach...

Pygmi

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Re: Ultra low power short range RF

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Ah,
If the Xemics and/or Aurel chips can give you the <50ms turn around time you
require, then absolutely go for one of these.
If not; do you have room in your budget for a combination of a low-power
receiver (the Aurel or Xemics or similar) and a high-speed transceiver with
short enough wakeup and turn around time? -


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Morten
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Re: Ultra low power short range RF

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you
with

The Aurel for example has a TX-RX turn around around 500 ms!!
On the other hand current drawn by Aurel inRX-mode is less than
that of  Xemics in CD detect mode.... And Xemics max. range with
considerable current draw in TX is about 3 m. So,  these are close,
and I guess I could go with one of these, but... I pretty sure there is
somewhere behind the corner a chip that fulfills all my needs...just
can't find it.

Your idea of having receiver and transmitter separately is one
option, I have thought about that too. But in order to make this
as simple as possible I would like to find two chip solution;
AVR + transceiver..

For example Atmel AT86RF211 has "wake-up" mode, but it's
cyclical wake-up, not continous monitoring of CD/data...
One of these days, I will find what I need or the solution for my
application is out date...well, either of these will stop the search...

   Pygmi



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