802.15.4 broadcasting and addressing

I’m using 3 XBee pro modules with one as master and 2 as slaves.

The master is addressed (16bit) with 0 and all the slaves with 1.

Each cycle the master broadcast a “synch” frame to the slaves, and each slave reply one by one using an overlying address.

Ive got issues when the second slave replies to the master. Is this issue linked with the addressing ? Does i use to have the same 16 bit address for every RF modules ?

I am not sure you have provided enough information as to what the issue is. If the issue is related to ACK’s not being properly received then it could be. The idea of retries and Acknowledgments is for the transmitting and receiving devices to know who send the data and for an ACK to be received. When you use the same 16 bit address on all of your remote nodes, your base has not way to know who the ACK is for. As a result it is possible for you to receive an ACK but receive it on the wrong transmitter. To resolve this try using a unique 16 bit address on each of the remote modules. Then use the Broadcast address on the base (0xFFFF).