diff --git a/cpu/avr/radio/rf230bb/atmega128rfa1_registermap.h b/cpu/avr/radio/rf230bb/atmega128rfa1_registermap.h
index 0c7bd53cb..3edd23cab 100644
--- a/cpu/avr/radio/rf230bb/atmega128rfa1_registermap.h
+++ b/cpu/avr/radio/rf230bb/atmega128rfa1_registermap.h
@@ -73,6 +73,12 @@
 #define RG_CSMA_BE            CSMA_BE
 #define RG_CSMA_SEED_0        CSMA_SEED_0
 #define RG_PHY_RSSI           PHY_RSSI
+#define SR_CCA_MODE           0x08, 0x60, 5
+//#define SR_CCA_CS_THRES       0x09, 0xf0, 4
+#define SR_CCA_ED_THRES        0x09, 0x0f, 0
+#define SR_CCA_REQUEST         0x08, 0x80, 7
+#define SR_CCA_DONE            0x01, 0x80, 7
+#define SR_CCA_STATUS          0x01, 0x40, 6
 
 
 /* RF230 register assignments, for reference */
diff --git a/cpu/avr/radio/rf230bb/rf230bb.c b/cpu/avr/radio/rf230bb/rf230bb.c
index 19aa8b253..9ee74f3f5 100644
--- a/cpu/avr/radio/rf230bb/rf230bb.c
+++ b/cpu/avr/radio/rf230bb/rf230bb.c
@@ -209,8 +209,7 @@ static int rf230_receiving_packet(void);
 static int pending_packet(void);
 static int rf230_cca(void);
 
-signed char rf230_last_rssi;
-uint8_t rf230_last_correlation;
+uint8_t rf230_last_correlation,rf230_last_rssi,rf230_smallest_rssi;
 
 const struct radio_driver rf230_driver =
   {
@@ -714,6 +713,24 @@ rf230_init(void)
   hal_register_write(RG_CSMA_SEED_0,hal_register_read(RG_PHY_RSSI) );//upper two RSSI reg bits RND_VALUE are random in rf231
  // hal_register_write(CSMA_SEED_1,42 );
 
+  /* CCA Mode Mode 1=Energy above threshold  2=Carrier sense only  3=Both 0=Either (RF231 only) */
+//hal_subregister_write(SR_CCA_MODE,1);  //1 is the power-on default
+
+  /* Carrier sense threshold (not implemented in RF230 or RF231) */
+// hal_subregister_write(SR_CCA_CS_THRES,1);
+
+  /* CCA energy threshold = -91dB + 2*SR_CCA_ED_THRESH. Reset defaults to -77dB */
+  /* Use RF230 base of -91;  RF231 base is -90 according to datasheet */
+#if RF230_CONF_CCA_THRES < -91
+#warning RF230_CONF_CCA_THRES below hardware limit, setting to -91dBm
+  hal_subregister_write(SR_CCA_ED_THRES,0);  
+#elif RF230_CONF_CCA_THRES > -61
+#warning RF230_CONF_CCA_THRES above hardware limit, setting to -61dBm
+  hal_subregister_write(SR_CCA_ED_THRES,15);  
+#else
+  hal_subregister_write(SR_CCA_ED_THRES,(RF230_CONF_CCA_THRES+91)/2);  
+#endif
+
   /* Use automatic CRC unless manual is specified */
 #if RF230_CONF_CHECKSUM
   hal_subregister_write(SR_TX_AUTO_CRC_ON, 0);
@@ -883,7 +900,6 @@ rf230_transmit(unsigned short payload_len)
   }
 
   RELEASE_LOCK();
-
   if (tx_result==1) {               //success, data pending from adressee
     tx_result=0;                    //Just show success?
   } else if (tx_result==3) {        //CSMA channel access failure
@@ -1332,6 +1348,10 @@ if (RF230_receive_on) {
 #endif
 #endif /* speed vs. generality */
 
+  /* Save the smallest rssi. The display routine can reset by setting it to zero */
+  if ((rf230_smallest_rssi==0) || (rf230_last_rssi<rf230_smallest_rssi))
+     rf230_smallest_rssi=rf230_last_rssi;
+
  //   rf230_last_correlation = rxframe[rxframe_head].lqi;
     packetbuf_set_attr(PACKETBUF_ATTR_RSSI, rf230_last_rssi);
     packetbuf_set_attr(PACKETBUF_ATTR_LINK_QUALITY, rf230_last_correlation);
@@ -1451,10 +1471,18 @@ rf230_cca(void)
     rf230_on();
   }
 
- // cca = CCA_IS_1;
   DEBUGFLOW('c');
-  cca=1;
+  /* CCA Mode Mode 1=Energy above threshold  2=Carrier sense only  3=Both 0=Either (RF231 only) */
+  /* Use the current mode. Note triggering a manual CCA is not recommended in extended mode */
+//hal_subregister_write(SR_CCA_MODE,1);
 
+  /* Start the CCA, wait till done, return result */
+  hal_subregister_write(SR_CCA_REQUEST,1);
+  delay_us(TIME_CCA);
+//while ((hal_register_read(RG_TRX_STATUS) & 0x80) == 0 ) {continue;}
+  while (!hal_subregister_read(SR_CCA_DONE)) {continue;}
+  cca=hal_subregister_read(SR_CCA_STATUS);
+  
   if(radio_was_off) {
     rf230_off();
   }
@@ -1481,4 +1509,3 @@ pending_packet(void)
   return pending;
 }
 /*---------------------------------------------------------------------------*/
-
diff --git a/cpu/avr/radio/rf230bb/rf230bb.h b/cpu/avr/radio/rf230bb/rf230bb.h
index e8c79d58a..718113c22 100644
--- a/cpu/avr/radio/rf230bb/rf230bb.h
+++ b/cpu/avr/radio/rf230bb/rf230bb.h
@@ -214,8 +214,7 @@ uint8_t rf230_get_txpower(void);
 void rf230_set_promiscuous_mode(bool isPromiscuous);
 bool rf230_is_ready_to_send();
 
-extern signed char rf230_last_rssi;
-extern uint8_t rf230_last_correlation;
+extern uint8_t rf230_last_correlation,rf230_last_rssi,rf230_smallest_rssi;
 
 uint8_t rf230_get_raw_rssi(void);
 
@@ -223,4 +222,4 @@ uint8_t rf230_get_raw_rssi(void);
 
 #endif
 /** @} */
-/*EOF*/
+/*EOF*/
\ No newline at end of file
diff --git a/platform/avr-ravenusb/cdc_task.c b/platform/avr-ravenusb/cdc_task.c
index c1c4b0483..1b0d46413 100644
--- a/platform/avr-ravenusb/cdc_task.c
+++ b/platform/avr-ravenusb/cdc_task.c
@@ -562,7 +562,12 @@ extern uip_ds6_netif_t uip_ds6_if;
 				PRINTF_P(PSTR("  * Operates on channel %d\n\r"), rf230_get_channel());
 				PRINTF_P(PSTR("  * TX Power(0=3dBm, 15=-17.2dBm): %d\n\r"), rf230_get_txpower());
 #endif
-				PRINTF_P(PSTR("  * Current/Last RSSI: %d/%ddBm\n\r"), -91+(rf230_rssi()-1), -91+(rf230_last_rssi-1));
+                if (rf230_smallest_rssi) {
+                    PRINTF_P(PSTR("  * Current/Last/Smallest RSSI: %d/%d/%ddBm\n\r"), -91+(rf230_rssi()-1), -91+(rf230_last_rssi-1),-91+(rf230_smallest_rssi-1));
+                    rf230_smallest_rssi=0;
+                } else {
+                    PRINTF_P(PSTR("  * Current/Last/Smallest RSSI: %d/%d/--dBm\n\r"), -91+(rf230_rssi()-1), -91+(rf230_last_rssi-1));
+                }
 
 #else /* RF230BB */
 				PRINTF_P(PSTR("  * Operates on channel %d\n\r"), radio_get_operating_channel());
diff --git a/platform/avr-ravenusb/contiki-conf.h b/platform/avr-ravenusb/contiki-conf.h
index aa9426b41..f89d99066 100644
--- a/platform/avr-ravenusb/contiki-conf.h
+++ b/platform/avr-ravenusb/contiki-conf.h
@@ -266,11 +266,16 @@ extern void mac_log_802_15_4_rx(const uint8_t* buffer, size_t total_len);
 /* AUTOACK receive mode gives better rssi measurements, even if ACK is never requested */
 #define RF230_CONF_AUTOACK        1
 /* Request 802.15.4 ACK on all packets sent by sicslowpan.c (else autoretry) */
-/* Broadcasts will be duplicated by the retry count! */
+/* Broadcasts will be duplicated by the retry count, since no one will ACK them! */
 #define SICSLOWPAN_CONF_ACK_ALL   0
 /* Number of auto retry attempts 0-15 (0 implies don't use extended TX_ARET_ON mode with CCA) */
 #define RF230_CONF_AUTORETRIES    1
+/* CCA theshold energy -91 to -61 dBm (default -77). Set this smaller than the expected minimum rssi to avoid packet collisions */
+/* The Jackdaw menu 'm' command is helpful for determining the smallest ever received rssi */
+#define RF230_CONF_CCA_THRES    -85
+/* Allow 6loWPAN fragmentation (more efficient for large payloads over a reliable channel) */
 #define SICSLOWPAN_CONF_FRAG      1
+/* Timeout for fragment reassembly. A reissued browser GET will also cancel reassembly, typically in 2-3 seconds */
 #define SICSLOWPAN_CONF_MAXAGE    3
 
 #elif 0  /* Contiki-mac radio cycling */