From 388e8efeb6bd556a190142624a5c7aeb9dbf97bb Mon Sep 17 00:00:00 2001
From: Roger Clark <roger@rogerclark.net>
Date: Mon, 18 Jul 2016 16:20:24 +1000
Subject: [PATCH] Fixed issue in F1 and F3 with HardwareSerial read(), which
 should return -1 if no data in the input buffer, (be non-blocking)

---
 STM32F1/cores/maple/HardwareSerial.cpp        |  9 +++++----
 STM32F3/cores/maple/wirish/HardwareSerial.cpp | 11 ++++++-----
 STM32F3/cores/maple/wirish/HardwareSerial.h   |  2 +-
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/STM32F1/cores/maple/HardwareSerial.cpp b/STM32F1/cores/maple/HardwareSerial.cpp
index 894470d..44ad460 100644
--- a/STM32F1/cores/maple/HardwareSerial.cpp
+++ b/STM32F1/cores/maple/HardwareSerial.cpp
@@ -159,10 +159,11 @@ void HardwareSerial::end(void) {
  */
 
 int HardwareSerial::read(void) {
-    // Block until a byte becomes available, to save user confusion.
-    while (!this->available())
-        ;
-    return usart_getc(this->usart_device);
+	if(usart_data_available(usart_device) > 0) {
+		return usart_getc(usart_device);
+	} else {
+		return -1;
+	}
 }
 
 int HardwareSerial::available(void) {
diff --git a/STM32F3/cores/maple/wirish/HardwareSerial.cpp b/STM32F3/cores/maple/wirish/HardwareSerial.cpp
index c4cb5f8..87f80d1 100644
--- a/STM32F3/cores/maple/wirish/HardwareSerial.cpp
+++ b/STM32F3/cores/maple/wirish/HardwareSerial.cpp
@@ -118,11 +118,12 @@ void HardwareSerial::end(void) {
  * I/O
  */
 
-uint8 HardwareSerial::read(void) {
-    // Block until a byte becomes available, to save user confusion.
-    while (!this->available())
-        ;
-    return usart_getc(this->usart_device);
+int HardwareSerial::read(void) {
+	if(usart_data_available(usart_device) > 0) {
+		return usart_getc(usart_device);
+	} else {
+		return -1;
+	}
 }
 
 uint32 HardwareSerial::available(void) {
diff --git a/STM32F3/cores/maple/wirish/HardwareSerial.h b/STM32F3/cores/maple/wirish/HardwareSerial.h
index f25362b..260a99e 100644
--- a/STM32F3/cores/maple/wirish/HardwareSerial.h
+++ b/STM32F3/cores/maple/wirish/HardwareSerial.h
@@ -62,7 +62,7 @@ public:
 
     /* I/O */
     uint32 available(void);
-    uint8 read(void);
+    int read(void);
     void flush(void);
     virtual void write(unsigned char);
     using Print::write;