save last_rssi reading after packet received

adafruit_rfm69.py

@@ -345,6 +345,8 @@ def __init__(self, spi, cs, reset, frequency, *, sync_word=b'\x2D\xD4',
         self.encryption_key = encryption_key
         # Set transmit power to 13 dBm, a safe value any module supports.
         self.tx_power = 13
+        # last RSSI reading
+        self.last_rssi = 0.
 
     # pylint: disable=no-member
     # Reconsider this disable when it can be tested.
@@ -765,6 +767,8 @@ def receive(self, timeout=0.5, keep_listening=True, with_header=False,
                     timed_out = True
         # Payload ready is set, a packet is in the FIFO.
         packet = None
+        # save RSSI
+        self.last_rssi = self.rssi
         # Enter idle mode to stop receiving other packets.
         self.idle()
         if timed_out:

examples/rfm69_rpi_interrupt.py

@@ -23,7 +23,7 @@ def rfm69_callback(rfm69_irq):
             # Print out the raw bytes of the packet:
             print('Received (raw bytes): {0}'.format(packet))
             print([hex(x) for x in packet])
-            print('RSSI: {0}'.format(rfm69.rssi))
+            print('RSSI: {0}'.format(rfm69.last_rssi))
 
 
 # Define radio parameters.