Jee Labs Talk

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1. charlie
   

   I was looking for a way to find out the ID of the node sending a transmission and it seems that the header described in http://news.jeelabs.org/docs/rf12.html contains the src/dst/ack

   src and dst look like the souceNodeId and destinationNodeId, but I don't quite understand the "ack", what could it mean?

   Furthermore I was looking for a way to find out that if you receive something that was sent using RF12.send(). Can you then somehow still access the header info, e.g. to find out the nodeId of the sender? (as to respond back)

   I am aware of the return path in the ack-s during easysend, but that's not what I'm after. I will store the remote nodeId to respond to it some later..

   Thanks

   Charlie

   Posted 26/01/2010 21:30:17

2. jcw
   

   There is one header byte with 8 bits - 5 bits are reserved for either source or destination node ID. The other 3 bits are flag bits (whether the ID is src or dst, and whether the packet is a normal data packet or an ACK). There are several combinations in there which have never been used, I intend to reorganize things slightly to support a 1-bit "sequence number" in the future. This requires some more work for the central receiver (for which I use RF12demo), so I haven't quite got to that yet.

   If you want to listen for incoming packets, then you can't use the easy transmit functions, you'll need to call rf12recvDone yourself, see RF12demo for some example code.

   The received header byte is available as "rf12hdr", it's valid at the same time as rf12len and rf12data, i.e. when rf12recvDone returns true.

   Posted 27/01/2010 10:30:13

3. smihai
   

   About the subject of the topic identify sender nodeId
   I've tried using Serial.print(rf12hdr, BIN); and trying to get the sender nodeId from there but with no success, any suggestions on how i could get the nodeId of a package i receive ?
   I have 3 sender nodes each with their nodeId setup and would like to see the nodeId of the received data so that i can corelate the data (temperature in this case) received from the node.

   Mihai

   Posted 27/01/2010 21:11:33

4. smihai
   

   I've just figured this out myself (i hope i'm right)
   The nodeID is sent in the header data (available through rf12hdr), and it's the last 5 bits of the package.
   For example:
   rf12hdr = 101001 (the node ID is 01001 Binary => 9 Decimal)
   In order to get the value i made
   101001 - 100000 = 01001 (binary)
   rf12hdr - 32 = 9 (decimal)

   Insert the folowing line after Serial.print((int) rf12hdr); in the RF12DEMO for an example

   Serial.print("\n node id: "); Serial.print(rf12hdr-32,DEC);

   If there's any error please let me know, as i am still new and learning this stuff. ;)

   Mihai

   Posted 27/01/2010 21:25:35

5. kellerza
   

   @Milhai

   It is the last 5 bits of the first byte as you said (or the first 5 depending on how you look at it). You want to get rid of the first three bits, so you should use AND to accomplish this.

   With the bits you want you should AND with 0x1F (or 0001 1111): 0x1F & rf12hdr

   Not that jcw has added a constant for 0x1F in the header: RF12HDRMASK, so you could do:

   RF12HDRMASK & rf12hdr

   The RF12 driver currently only sends source during broadcasts. I'm working on an overlay for the RF12 driver, see
   http://talk.jeelabs.net/topic/98 if your interested.
   At the moment I'm using a ring buffer, but its still blocks sometimes, so not quite finished yet. For now I do retransmits (works ok with my 3 deployed nodes). I should probably post the progress, some more eyes won't hurt :)

   -Johann

   Posted 28/01/2010 15:33:20