Jee Labs Talk

This forum has moved to forum.jeelabs.net - this read-only archive is for reference only!

1. joop
   

   see this link last post from ansel

   Is it possible to receive OOK without extra hardware on a jee-node ?, I don't read they use any extra hardware ,or maybe I am missing something.

   Posted 07/07/2010 17:36:23

2. jcw
   

   Interesting! All I see in the code is that an extra "DATA" pin has been hooked up as digital input. I wonder which pin that is. Haven't looked closer yet - could it be that he's putting the RFM12B in a special mode and then reading out the FSK/DATA pin?

   Posted 07/07/2010 21:13:59

3. joop
   

   Yes that could be the trick,I 'll try to find more info .(FSK/DATA)

   Posted 08/07/2010 06:56:04

4. andras
   

   The RFM12B is probably has FIFO mode disabled in the configuration setting register. When receiving, the raw data is then available on the DATA/FSK/FSS pin (not connected on the Jeenode).

   When an OOK tranmitter is sending and the send frequency corresponds to the RF12 center+deviation frequency, the DATA pin is set high. However, this doesn't mean that it returns nicely to zero when the OOK transmitter stops sending; that would only happen if there were a signal on the center-deviation frequency.

   In the absence of a signal, the RF12 will try to get a signal out of the noise and the DATA pin will randomly flipper between 1 and 0. I suppose you could extract an OOK signal from this behaviour if the flippering happens relatively frequently.

   BTW: I didn't come up with this myself. On the Silabs site there is a document called "RF Wireless foundation course book one" where this trick is described: under resources->documentation->miscelaneous

   Posted 13/07/2010 13:31:47

5. andras
   

   I did a little test to see how frequently the flippering in absence of a signal happens. I hooked up the DATA pin on a digital input pin and set the RF12 in non-fifo mode with:

       rf12control(0x80a7);

   The DATA signal indeed went about 1 and 0 randomly. However, it would frequently be in the same state for hundreds of usecs. I suppose that's too long to reliably distinguish the real OOK pulses (also in the order of hundreds of usecs) from the flippering, so it looks like this isn't going to work.

   Posted 29/09/2010 08:09:43

6. joop
   

   I tried this today .

       - soldered  a 100 ohm resistor to the  DATA/FSK/FSS pin and 
       to analog input 0 AI01 (interrupt OOK in) 

       I use the program 
       // Receive / decode FS20, (K)S300, and EM10 signals using an 868 MHz OOK radi0
       from jc .(but I can't find it in examples RF12.zip)

       The trick is the C220 command (c420), it is the command to set the RFM01 in
       OOK mode ,but it seems to work with a RFM12B.(with some difference) 
       andras ,FIFO is  disabled.

       The gain and RSI values (0x9481) are very important , the duty-cycle of the   
       signal depends on these values and the distance of the sender from the receiver
       so it is very hard to get the right values ,but I received OOK commands at 15
       meter distance ,maybe when using the analog filter this could be better,I keep
       on trying.

       registers values

       rf12xfer(0x8027); // 8027    868 Mhz;disabel tx register; disabel RX fifo buffer;  
       rf12xfer(0x82c0); // 82c0    enable receiver ; enable basebandblock 
       rf12xfer(0xA68a); // A68a    868.2500 MHz
       rf12xfer(0xc623); // c623    datarate 9579 kbps 
       rf12xfer(0x9481); // 9481    VDI; FAST;200khz;GAIN MAX;DRSSI 97dbm   
       rf12xfer(0xC220); // c220    datafiltercommand ;  not documented command is    
                                     from from RFM01 OOK-mode
       rf12xfer(0xCA00); // ca00    FiFo and resetmode command ; FIFO fill disabeld
       rf12xfer(0xC473); // c473    AFC run only once ; enable AFC ;enable frequency 
       rf12xfer(0xCC67); // cc67    pll settings command
       rf12xfer(0xB800); // NOT USE 
       rf12xfer(0xC800); // NOT USE 
       rf12xfer(0xC040); // 1.66MHz,2.2V   

       see this link 
   
   
   

   Posted 07/10/2010 18:32:48

7. andras
   

   Hi Joop,

   Mysterious stuff, those undocumented features. Makes you wonder wether there are any other hidden capabilities...

   In found jcw's FS20 receive/decode sketch here:

   Posted 08/10/2010 14:04:36

8. joop
   

   andras ,thank you for the link , it is the recv868fs20.pde sketch.

   Posted 08/10/2010 15:44:45

9. joop
   

   Hello ,I am trying to set the right RFM12 DATA rate is this right ? 1.666kbps

   // bit = 0: 400µs High, 400µs Low average period 600-1000µs shortest 600uS // bit = 1: 600µs High, 600µs Low average period 1000-1450µs // bit = 0 minimal 600uS = 0.000600 = 1/0.0006 = 1.666 kbps

   Posted 12/10/2010 16:00:04

10. joop
    

    Last month I tried something ,I replaced the the Carssi capacitor from the RFM12B(ver3) with a value 150 pf,with good results, now the sensitivity (FS20 protocol) is good on short and long distances.

         sensitivity antenna's different lengths free air

         868 1/4 wave = 82.2mm    sensitivity ok 0.7 - 70 meter
         868 1/2 wave = 164.3mm   sensitivity ok 0.7 - 100 meter
         868 full wave = 345.5mm  sensitivity ok 0.7 - 120 meter

    I use one RFM12B now,to send and receive FS20-packets over wireless,it performs well inhouse and to the shed.

    More info on this link.

    OOKASKwithamodifiedRFM12B>

    Posted 12/12/2010 09:48:40

11. andras
    

    Those are good results indeed ! If the FSK operation keeps working as well with this 150pf capacitor, I suppose that in addition to some local OOK task, one could als have that Jeenode act as OOK gateway by listening in OOK mode and switching only briefly to FSK mode after a succesfull OOK reception to send the OOK data to the central node over FSK.

    Posted 14/12/2010 14:47:13

12. joop
    

    Yes good idee ,and that same Jeenode could also control a RF Remote control mains switch ,when this command is transmitted by the central node.

    I haven't tested the FSK-operations yet with this modification, I mainly use the jeenodes for transmitting and receiving FS20.

    Posted 15/12/2010 18:24:43