[Tinyos-help] CC2420 Hardware or software Ack

[Anton]

Sorry, I was wrong.

PacketAcknowledgements.requestAck() is necessary when HW acks are used 
(to set the acknowledgment request field in the packet).

Also, if acknowledgments are enabled (no matter SW or HW), the second 
negative CCA-pulse should appear (on the CCA-pin of the sender radio 
chip) which corresponds to the acknowledgment (the first CCA-pulse 
corresponds to the packet itself). When HW-acks are used, that second 
pulse appears 128 microseconds after the first one. When SW-acks are 
used that second pulse appears 880 microseconds after the first one. 
This means that SW-ack appears in the channel 752 microseconds later 
than HW-ack. So, apart from the differences between SW- and HW-acks 
mentioned in TEP126, there is a difference in terms of time: the 
receiver responds with software acks little bit later than with hardware 
acks.

Anton.