From 65b4a24d639d3b4d03779ac33c9e7f684407ff81 Mon Sep 17 00:00:00 2001
From: Joost Yervante Damad <joost@damad.be>
Date: Tue, 7 Feb 2012 08:53:31 +0100
Subject: [PATCH] Introduce writeable call on HardwareSerial. Can be used e.g.
 to do some form of flow control between multiple Serial devices on an Arduino
 Mega.

---
 hardware/arduino/cores/arduino/HardwareSerial.cpp | 6 ++++++
 hardware/arduino/cores/arduino/HardwareSerial.h   | 1 +
 2 files changed, 7 insertions(+)

diff --git a/hardware/arduino/cores/arduino/HardwareSerial.cpp b/hardware/arduino/cores/arduino/HardwareSerial.cpp
index 9985b78c6e4..0adbe250d6f 100644
--- a/hardware/arduino/cores/arduino/HardwareSerial.cpp
+++ b/hardware/arduino/cores/arduino/HardwareSerial.cpp
@@ -380,6 +380,12 @@ void HardwareSerial::flush()
     ;
 }
 
+bool HardwareSerial::writeable()
+{
+  int i = (_tx_buffer->head + 1) % SERIAL_BUFFER_SIZE;
+  return (i != _tx_buffer->tail);
+}
+
 size_t HardwareSerial::write(uint8_t c)
 {
   int i = (_tx_buffer->head + 1) % SERIAL_BUFFER_SIZE;
diff --git a/hardware/arduino/cores/arduino/HardwareSerial.h b/hardware/arduino/cores/arduino/HardwareSerial.h
index 176abe1e20b..413fe9a026b 100644
--- a/hardware/arduino/cores/arduino/HardwareSerial.h
+++ b/hardware/arduino/cores/arduino/HardwareSerial.h
@@ -55,6 +55,7 @@ class HardwareSerial : public Stream
     virtual int peek(void);
     virtual int read(void);
     virtual void flush(void);
+    virtual bool writeable(void);
     virtual size_t write(uint8_t);
     using Print::write; // pull in write(str) and write(buf, size) from Print
 };