Matt Keally's Blog

I’ve seen a lot of questions about how to enable ACKs in TinyOS and not too many responses. Unlike a lot of TinyOS problems I’ve had, this one isn’t too bad. Some sample code for enabling ACKs is available in $TOSROOT/apps/tests/cc2420/TestAcks. In your configuration .nc file, just wire the PacketAcknowledgements interface:

implementation {
...
MainC.PacketAcknowledgements -> ActiveMessageC;
}

Then, in your implementation file:

module TestAcksP {
uses {
interface PacketAcknowledgements;
...

Then, just before you call AMSend.send() for a message_t testMsg:

call PacketAcknowledgements.requestAck(&testMsg);

When a packet arrives with an ACK request, the ACK will be sent automatically. In the sender’s AMSend.sendDone(), you will want to make sure the packet was ACKed to determine if a retransmission is required:

if(!call PacketAcknowledgements.wasAcked(&testMsg))
retransmit();

And that’s pretty much it.