diff --git a/pizzactrl/hal_serial.py b/pizzactrl/hal_serial.py
index d994eb9..672b626 100644
--- a/pizzactrl/hal_serial.py
+++ b/pizzactrl/hal_serial.py
@@ -151,8 +151,12 @@ def turn_off(hal: PizzaHAL):
     hal.send_cmd(SerialCommands.FRONTLIGHT, 0)
 
 
-def wait_for_input(hal: PizzaHAL, go_callback: Any,
-                   back_callback: Any, to_callback: Any,
+def wait_for_input(hal: PizzaHAL,
+                   blue_callback: Any = None,
+                   red_callback: Any = None,
+                   yellow_callback: Any = None,
+                   green_callback: Any = None,
+                   timeout_callback: Any = None,
                    timeout=120, **kwargs):
     """
     Blink leds on buttons. Wait until the user presses a button, then execute
@@ -164,13 +168,28 @@ def wait_for_input(hal: PizzaHAL, go_callback: Any,
     :param to_callback: called on timeout
     :param timeout: inactivity timeout in seconds (default 120)
     """
-    resp = hal.send_cmd(SerialCommands.USER_INTERACTION, timeout).strip()
-    if resp == b'B':
-        go_callback(**kwargs)
-    elif resp == b'R':
-        back_callback(**kwargs)
-    else:
-        to_callback(**kwargs)
+    timeout *= 1000
+
+    bitmask = (1 if blue_callback else 0) | \
+              (2 if red_callback else 0) | \
+              (4 if yellow_callback else 0) | \
+              (8 if green_callback else 0)
+
+    resp = hal.send_cmd(SerialCommands.USER_INTERACT, bitmask.to_bytes(1, 'little', signed=False), timeout.to_bytes(4, 'little', signed=False))
+    if (not resp.startswith(SerialCommands.RECEIVED.value)) or (len(resp) != 3):
+        raise SerialCommunicationError(f'USER_INTERACTION received {resp} (expected 3 bytes, starting with 0x03)')
+    
+    resp = resp[1]
+    if resp == 1:
+        blue_callback(**kwargs)
+    elif resp == 2:
+        red_callback(**kwargs)
+    elif resp == 4:
+        yellow_callback(**kwargs)
+    elif resp == 8:
+        green_callback(**kwargs)
+    elif timeout_callback is not None:
+        timeout_callback(**kwargs)
 
 
 def light_layer(hal: PizzaHAL, r: float, g: float, b: float, w: float, fade: float = 0.0, **kwargs):
@@ -213,7 +232,7 @@ def backlight(hal: PizzaHAL, r: float, g: float, b: float, w: float, fade: float
                  int(fade * 1000).to_bytes(4, 'little'))
 
 
-def play_sound(hal: PizzaHAL, sound: Any, **kwargs):
+def play_sound(hal: PizzaHAL, sound: Any, interruptable: bool = False, **kwargs):
     """
     Play a sound.
 
@@ -222,6 +241,7 @@ def play_sound(hal: PizzaHAL, sound: Any, **kwargs):
     """
     # Extract data and sampling rate from file
     try:
+        # TODO implement interruption
         data, fs = hal.soundcache.get(str(sound), sf.read(str(sound), dtype='float32'))
         sd.play(data, fs)
         sd.wait()  # Wait until file is done playing
@@ -243,11 +263,11 @@ def record_sound(hal: PizzaHAL, filename: Any, duration: float,
     myrecording = sd.rec(int(duration * AUDIO_REC_SR),
                          samplerate=AUDIO_REC_SR,
                          channels=2)
-    resp = hal.send_cmd(SerialCommands.RECORD, int(duration)).strip()
-    if resp == b'I':
-        sd.stop()
-    else:
-        sd.wait()  # Wait until recording is finished
+    
+    hal.send_cmd(SerialCommands.RECORD, int(duration).to_bytes(4, 'little', signed=False))
+
+    sd.stop()
+    
     writewav(str(filename), AUDIO_REC_SR, myrecording)
     if cache:
         hal.soundcache[str(filename)] = (myrecording, AUDIO_REC_SR)
diff --git a/pizzactrl/hal_test.py b/pizzactrl/hal_test.py
new file mode 100644
index 0000000..4d5c04a
--- /dev/null
+++ b/pizzactrl/hal_test.py
@@ -0,0 +1,4 @@
+from . import hal_serial
+
+hal = hal_serial.PizzaHAL()
+