From f8b124b78cd9855a09499f23dbf38c84685f6d60 Mon Sep 17 00:00:00 2001
From: Carlo Parata <carlo.parata@st.com>
Date: Thu, 3 Aug 2017 10:49:13 +0200
Subject: [PATCH] Fix possible issue on serial ports

---
 cores/arduino/HardwareSerial.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index d15e5c5aff..dc2306a42d 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -70,14 +70,13 @@ int HardwareSerial::_tx_complete_irq(serial_t* obj)
 {
   // If interrupts are enabled, there must be more data in the output
   // buffer. Send the next byte
-  unsigned char c = obj->tx_buff[obj->tx_tail];
   obj->tx_tail = (obj->tx_tail + 1) % SERIAL_TX_BUFFER_SIZE;
 
   if (obj->tx_head == obj->tx_tail) {
     return -1;
   }
 
-  return c;
+  return 0;
 }
 
 // Public Methods //////////////////////////////////////////////////////////////