CC2420 Hardware and Software Acks

Originally, the CC2420 radio stack only used hardware generated auto-acknowledgements provided by the CC2420 chip itself. This led to some issues, such as false acknowledgements where the radio chip would receive a packet and acknowledge its reception and the microcontroller would never actually receive the packet.

The current CC2420 stack uses software acknowledgements, which have a higher drop percentage. When used with the UniqueSend and UniqueReceive interfaces, dropped acknowledgements are more desirable than false acknowledgements. Received packets are always acknowledged before being filtered as a duplicate.

Use the PacketAcknowledgements or PacketLink interfaces to determine if a packet was successfully acknowledged.

Acknowledgment Controls

Defining the preprocessor variable CC2420_NO_ACKNOWLEDGEMENTS will disable all forms of acknowledgments at compile time.

Defining the preprocessor variable CC2420_HW_ACKNOWLEDGEMENTS will enable hardware acknowledgments and disable software acknowledgments.

Acknowledgments can also be toggled at run-time by accessing the CC2420Config interface provided by CC2420ControlC. Be sure to sync() the hardware if you reconfigure the CC2420 radio at runtime.

 /**
  * Sync must be called for acknowledgement changes to take effect
  * @param enableAutoAck TRUE to enable auto acknowledgements
  * @param hwAutoAck TRUE to default to hardware auto acks, FALSE to
  *     default to software auto acknowledgements
  */
 command void CC2420Config.setAutoAck(bool enableAutoAck, bool hwAutoAck) {
   atomic autoAckEnabled = enableAutoAck;
   atomic hwAutoAckDefault = hwAutoAck;
 }
 
 /**
  * @return TRUE if hardware auto acks are the default, FALSE if software
  *     acks are the default
  */
 async command bool CC2420Config.isHwAutoAckDefault() {
   atomic return hwAutoAckDefault;    
 }
 
 /**
  * @return TRUE if auto acks are enabled
  */
 async command bool CC2420Config.isAutoAckEnabled() {
   atomic return autoAckEnabled;
 }
 

See Also

• CC2420

Next

• CC2420 Data Sequence Numbers