Forum Post: RE: I cannot get the CCA working in either CC2500 or CC1101

I only have experience on 1121, so this might not apply. In order to do a CCA, the RSSI must be valid (otherwise CCA decision is based on incorrect information). After a RX strobe it will take some time until the RSSI is valid. Check DN505 for more information: http://www.ti.com/lit/an/swra114d/swra114d.pdf