From 40cbe0de432c32e020857fe4a801fb4b4db34503 Mon Sep 17 00:00:00 2001
From: Martino Facchin <m.facchin@arduino.cc>
Date: Wed, 11 Mar 2020 12:32:49 +0100
Subject: [PATCH] Tone: allow running indefinitely when called without duration

---
 cores/arduino/Tone.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/cores/arduino/Tone.cpp b/cores/arduino/Tone.cpp
index 29a5842d..d30e0d79 100644
--- a/cores/arduino/Tone.cpp
+++ b/cores/arduino/Tone.cpp
@@ -21,7 +21,9 @@ class Tone {
 
     void start(void) {
         ticker.attach(mbed::callback(this, &Tone::toggle), 0.5f / float(frequency));
-        start_timeout();
+        if (duration != 0) {
+            start_timeout();
+        }
     }
 
     void toggle() {