not a support questionI went thru the demo sketches but I have some difficulties to use the RF12 library.
I would like to send strings from a central node to different remote nodes:
for eg "command1" to node1 "command3" to node5
I hope that somebody can give me some hints, can point me to the right direction,
any sample code on how to send the payload and address a specific node would be great !
many thanks,
jean-louis
Untested:
[code]
if (want_to_send && rf12_canSend()) {
if (...)
rf12_sendData(1, "command1", 8);
else
rf12_sendData(5, "command3", 8);
want_to_send = 0;
}
[/code]
(the "8" is the number of bytes to send)
Aha - now I get it. Ok, this is where the simple scheme in RF12 may start to bite...
You can send a packet to node X, but then X won't know where it's from.
Or you can broadcast to anyone, then all receivers will know who sent it.
The difference is indicated by the RF12_HDR_DST bit in the header.
That's because there is only *either* a destination *or* a source address in the packet header. The reason is that it's enough for basic communication, so I decided to try this minimal approach, and put any further info the app needs in the payload, without the RF12 driver needing to know where and how.
So if you want to filter, you need to include the source id in the payload, and then have the receivers ignore the ones they don't want.
But there's one problem with the above reasoning. The RF12 driver *does* have the logic to filter, so that node Y won't see packets sent to node X. It's in RF12.h, in recvDone(), the lines:
if (!(rf12_hdr & RF12_HDR_DST) || (rf12_hdr & RF12_HDR_MASK) == (nodeid & NODE_ID)) {
So I'm puzzled why it isn't working as expected... I'll look into this.
i also found out that i must set RF12_HDR_DST to send to exact node, i i need to send to node 3 then hdr must be 0x63 etc. As i understand - if i need "ack" i must bradcast and filter out unwanted signals on receiving unit right? And what flags must be set in HDR to broadcast, without using easySend?
Use 0 as broadcast node ID, i.e. pass RF12_HDR_ACK or 0 as first arg to rf12_sendStart(), depending on whether you want to get an ack or not, respectively.
You can send to a specific node and ask for an ack (RF12_HDR_ACK | RF12_HDR_DST | nodeid), but given the current minimal RF12 design, this means the receiver has to use broadcasting to get the ack back, since it can't tell from the header who sent it.
ok, i have this (example dest_node id 4):
0x64 (RF12_HDR_ACK | RF12_HDR_DST | dest_nodeid) - sends only to exact node, NO "ack"
0x20 (RF12_HDR_ACK) - broadcasts to all nodes and requests "ack"
0x24 (RF12_HDR_ACK | dest_nodeid) - same, broadcasts to all nodes and requests "ack"
0x44 (RF12_HDR_DST | dest_nodeid) - sends only to exact node, no "ack"
do i need to change "ack" code?
if (rf12_crc == 0 && (rf12_hdr & ~RF12_HDR_MASK) == RF12_HDR_ACK) {
uint8_t addr = rf12_hdr & RF12_HDR_MASK;
rf12_sendStart(RF12_HDR_CTL | RF12_HDR_DST | addr, 0, 0);
Serial.println("-->ack");
}
You must log in to post.
