source/NanostackRfPhySpirit1.cpp@64:28ef790e4ef7, 2017-07-03 (annotated)

Committer:

Wolfgang Betz

Date:

Mon Jul 03 14:39:01 2017 +0200

Revision:

64:28ef790e4ef7

Parent:

63:d7530f62ed93

Child:

65:a16f0064110a

Implement indications received by Kevin Bracey



Date: Mon, 3 Jul 2017 10:14:23 +0000

From: Kevin Bracey <notifications@github.com>



https://github.com/ARMmbed/mbed-os-example-client/issues/266#issuecomment-312606944



I've just spent a little while reviewing the Spirit driver code, just to see if I can see any obvious flaws. (Hard to say much without knowing the hardware, but I can look for general issues.)



I'm a bit wary about the software ack handling - can be tricky.



There is one specific problem that could be affecting performance now - it seems to me the acks are sent with a common send() routine that enables hardware CSMA-CD. An ack should be being sent 192us after transmission completion, without CSMA. Backing off the ack will greatly reduce the chance of packets being successfully acknowledged.



Other notes on ack reception - you're calling TX_DONE whenever tx_sequence == seq_number, whether you were expecting an ack or not. This could cause stack confusion in various ways (eg if you were backing off while someone else used the same sequence number). You should only process an ACK when you actually expect one (TX completed, and AR bit was set in it)



Also, while expecting an ack, it can be beneficial to report TX_FAIL and stop expecting when you receive anything other then an ack with the expected sequence number. The stack will eventually time out if it doesn't get TX_DONE, but receipt of anything else (including a wrongly-numbered ack) indicates a lack of acknowledgment, which can be reported immediately.

Who changed what in which revision?