Fix radio hangups when trying to transmit with radio off.

The border-router tries to transmit and do other stuff after turning
the radio off, and the radio driver didn't handle that very well.
With this fix, it's no longer necessary to reset the border router
after starting tunslip6.

cpu/arm/aducrf101/dev/radio.c

@@ -193,6 +193,9 @@ prepare(const void *payload, unsigned short payload_len)
 static int
 transmit(unsigned short transmit_len)
 {
+  if(!radio_is_on)
+    return RADIO_TX_ERR;
+
   /* Transmit the packet */
   if(transmit_len > MAX_PACKET_LEN) {
     transmit_len = MAX_PACKET_LEN;
@@ -224,6 +227,9 @@ read(void *buf, unsigned short buf_len)
   uint8_t packet_len;
   int8_t rssi;
 
+  if(!radio_is_on)
+    return 0;
+
   if(buf_len > MAX_PACKET_LEN) {
     buf_len = MAX_PACKET_LEN;
   }
@@ -296,7 +302,7 @@ get_value(radio_param_t param, radio_value_t *value)
   case RADIO_PARAM_RSSI:
   {
     int8_t dbm;
-    if(RadioRadioGetRSSI(&dbm) != RIE_Success) {
+    if(!radio_is_on || RadioRadioGetRSSI(&dbm) != RIE_Success) {
       return RADIO_RESULT_ERROR;
     }
     *value = dbm;

platform/ev-aducrf101mkxz/README.md

@@ -73,8 +73,7 @@ the SLIP tunnel on the host machine:
         -s /dev/serial/by-id/usb-SEGGER_J-Link_000541011111-if00 \
         -B 115200 -v3 aaaa::1/64
 
-Press the RESET button on the eval board, then open the border router
-home page at: http://[aaaa::3230:3030:3132:3334]/
+Open the border router's home page at: http://[aaaa::3230:3030:3132:3334]/
 
 #### Web Server ####