better output

control_iperf.py

@@ -179,7 +179,11 @@ async def async_main(args, devices):
     # Give a brief moment for all serial ports to open and "settle"
     await asyncio.sleep(0.5)
 
-    print(">>> TRIGGERING ALL DEVICES <<<")
+    if len(devices) > 1:
+        print(f">>> TRIGGERING {len(devices)} DEVICES <<<")
+    else:
+        print(f">>> TRIGGERING {devices[0]} <<<")
+
     sync_event.set() # Unblocks all devices instantly
 
     results = await asyncio.gather(*tasks)