[gnoduino] Backported 'yield()' hook from 1.5.x

[Lucian Langa <lucilanga src gnome org>]

commit 7595d48113dcfb39ef61d593a337143d1220ee6f
Author: Cristian Maglie <c maglie bug st>
Date:   Wed Oct 15 11:26:09 2014 +0200

    Backported 'yield()' hook from 1.5.x

 hardware/arduino/cores/arduino/Arduino.h |    2 +
 hardware/arduino/cores/arduino/hooks.c   |   31 ++++++++++++++++++++++++++++++
 hardware/arduino/cores/arduino/wiring.c  |    1 +
 3 files changed, 34 insertions(+), 0 deletions(-)
---
diff --git a/hardware/arduino/cores/arduino/Arduino.h b/hardware/arduino/cores/arduino/Arduino.h
index 2e69019..cc1759d 100755
--- a/hardware/arduino/cores/arduino/Arduino.h
+++ b/hardware/arduino/cores/arduino/Arduino.h
@@ -34,6 +34,8 @@
 extern "C"{
 #endif
 
+void yield(void);
+
 #define HIGH 0x1
 #define LOW  0x0
 
diff --git a/hardware/arduino/cores/arduino/hooks.c b/hardware/arduino/cores/arduino/hooks.c
new file mode 100644
index 0000000..641eabc
--- /dev/null
+++ b/hardware/arduino/cores/arduino/hooks.c
@@ -0,0 +1,31 @@
+/*
+  Copyright (c) 2012 Arduino.  All right reserved.
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the GNU Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+/**
+ * Empty yield() hook.
+ *
+ * This function is intended to be used by library writers to build
+ * libraries or sketches that supports cooperative threads.
+ *
+ * Its defined as a weak symbol and it can be redefined to implement a
+ * real cooperative scheduler.
+ */
+static void __empty() {
+       // Empty
+}
+void yield(void) __attribute__ ((weak, alias("__empty")));
diff --git a/hardware/arduino/cores/arduino/wiring.c b/hardware/arduino/cores/arduino/wiring.c
index bea99d1..75077b9 100644
--- a/hardware/arduino/cores/arduino/wiring.c
+++ b/hardware/arduino/cores/arduino/wiring.c
@@ -111,6 +111,7 @@ void delay(unsigned long ms)
        uint16_t start = (uint16_t)micros();
 
        while (ms > 0) {
+               yield();
                if (((uint16_t)micros() - start) >= 1000) {
                        ms--;
                        start += 1000;