Hello, I've browsed around and it appears the RFM12/RFM12B is well capable of receiving OOK (aka ASK) signals: This wiki page lists methods to decode signals - the necessary routines appear to be included in the "Ethersex" software and should be adoptable to Arduino. Anyone wanna help?
http://ethersex.de/index.php/HowToRFM12_ASK
And here is another one:
http://www.das-labor.org/wiki/RFM12_library
Ah, that's a great link - thanks! I'll look into this again. So far I've not been able to decode OOK signals via an RFM12B. Have been using external hardware instead, for now. Doing everything with the RFM12B would be nice.
Jean-Claude, that would be awesome. I want to work on this, but this is my first project on the Arduino so I'm looking for some ready-made libraries I can work with...
Here's my project:
My apartment has its own gas burner for heat/water. It used to waste a lot of energy especially at night so I bought some ELV/Conrad FHTs to control the radiators. However, that still does not shut off the burner when all radiator thermostat valves are closed. It occasionally fires up just to keep warm water ready.
Solution: Pick up FHT signals with the RFM, feed them to the Arduino, and use it to shut off the heater when all valves are closed.
If you want to shut off the heater to reduce energy consumption and not just to make it quieter at night, keep in mind that it'll have to heat up the hot water supply again in the morning. So you're basically saving the *difference* in standby losses over some 8h from having a cooling-down-but-not-cold water reserve. It might not save as much as expected...
Yes, I didn't describe this quite accurately. This heater is an "on-demand" heater (German: Gasetagenheizung) for both heating and warm water. It burns gas only when heat is needed, i.e. it has no warm water reservoir. However, there is of course water in the radiator piping. What happens is that it heats the water that is supposed to circulate through the radiators EVEN THOUGH all radiator valves are closed. This is simply because the heater has only one way of "knowing" whether the radiators demand heat: by the temperature of the water in the circuit.
Has anyone sorted out the OOK ASK Mode from (pin 4=FFIT)
off the RFM12 ,shown by the two links from danage, is this
trick possible ? , it's not in the datasheet RFM12B (SI4420 silicon labs).
Well I read not all the information on first link in the earlier post from
danage.
on this side Veyron wrote
HowToRFM12_ASK from Veyron
Veyron wrote
"Schaltet man im Menü auch RFM12 ASK external filterein, so ist es möglich an Pin 4 des
RFM12-Chips Empfangssignale zu messen. Dazu ist ein ECMD Aufruf nötig"
Durch einen kleinen Trick kann das RFM12 auch zum Schalten von Funksteckdosen verwendet werden. "
pin 4 = FFIT from the RFM12B I it is not connected ,to the jeenode.(yet)
I search for the rfm12_ask_external_filter_init() function , and I
found this in an old web buffer.
#ifdef RFM12_ASK_EXTERNAL_FILTER_SUPPORT
void
rfm12_ask_external_filter_init()
{
rfm12_prologue ();
rfm12_trans(0x82C0); // 2. PwrMngt TX off, enable whole receiver chain
rfm12_trans(0xC238); // 6. Data Filter Command
rfm12_epilogue ();
}
void
rfm12_ask_external_filter_deinit()
{
rfm12_init();
}
#endif // RFM12_ASK_EXTERNAL_FILTER_SUPPORT
So I started up de RF12demo , and connected a high impedance (crystal) earphone to
ground and pin 4 off the RFM 12B and I heard nothing as aspected,
Then I changed this two registers
rfm12_trans(0x82C0);
rfm12_trans(0xC238);
Started up RF12demo and to my suprise I heard a lot off noise, on pin 4 and when
I pressed my FS20 Remote I heard the bitstream , so something was coming trough.
There was a lot of noise , so maybe you could use it to decode FS20 with some
extra hardware .opamp or vco. (I don't no if it is good enough for FS20)
There is on the RFM12B an other output I think the quality is
better then pin4 ,it could be the RF signal before all filters and
decoders (I don't no this) , the disadvantage is that it isn't led to the sides
off the circuit-board.
When you look at the board off the rfm12 , crystal to the left,the most
top right C ,the most right connection of this c is the signal,maybe
this one could work,you need an op-amp or vco with this one.
Well it needs some more investigation.
Interesting detective work, Joop! When I tried ASK recently, I couldn't figure out how to pick up the signal. Even if some amplification is required, it would be very useful to pursue this, IMO - particularly if the result is a digital level which can be used to trigger pin-change interrupts, because then we would essentially get the equivalent of an ELV-type OOK receiver built-in. And the existing OOK decoder sketches would work as is. With analog levels, the ADC or comparator needs to be dedicated exclusively to this task.
FWIW, I briefly considered polling the RF12 status register continuously, but that essentially makes the RFM12B unusable for simultaneous reception of FSK signals. A separate pin interrupt would allow receiving *both* OOK/ASK and FSK with a single RFM12B - not at the same time of course, but by responding to whichever comes in.
The connection to the right of the C has been identified by seaton as the ARSSI signal. You can read more about this in his rfm12 tutorial on:
http://blog.strobotics.com.au/2008/06/17/rfm12-tutorial-part2/
This signal is featured as a pin on the chip version of the rf12, but somehow not on the module version (although it is mention in the featurelist of the module datasheet).
Reinhard Max has suggested that this could perhaps be used for OOK reception:
http://news.jeelabs.org/2009/05/18/trying-to-receive-ook-data/#comments
thank you for the link andras ,
---------------------------------------------
If the RSSI status bit is too slow, or polling it has too much jitter, you could try monitoring the ARSSI signal with an analog comparator or two.
See http://www.mikrocontroller.net/topic/65984#541030 for the location of the ARSSI signal on the RFM12(B).
Reinhard Max
18 May 2009 at 10am
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