Port Scheduler library to Arduino Zero.

Author: Peter Van Hoyweghen

libraries/Scheduler/library.properties

@@ -1,9 +1,9 @@
 name=Scheduler
-version=0.4.3
+version=0.4.4
 author=Arduino
 maintainer=Arduino <[email protected]>
-sentence=Allows multiple tasks to run at the same time, without interrupting each other. For Arduino DUE only.
-paragraph=The Scheduler library enables the Arduino Due to run multiple functions at the same time. This allows tasks to happen without interrupting each other.</br>This is a cooperative scheduler in that the CPU switches from one task to another. The library includes methods for passing control between tasks.
+sentence=Allows multiple tasks to run at the same time, without interrupting each other. For Arduino sam and samd cores only (Due, Zero...).
+paragraph=The Scheduler library enables the Arduino to run multiple functions at the same time. This allows tasks to happen without interrupting each other.</br>This is a cooperative scheduler in that the CPU switches from one task to another. The library includes methods for passing control between tasks.
 category=Other
 url=http://www.arduino.cc/en/Reference/Scheduler
 architectures=sam

libraries/Scheduler/src/Scheduler.cpp

@@ -54,21 +54,68 @@ static void __attribute__((naked)) __attribute__((noinline)) coopTaskStart(void)
 		"mov   r0, r5;"
 		"blx   r4;"
 		"mov   r0, #1;"
+		/* shedule. address of next task context is put in r0 */
 		"bl    coopSchedule;"
+#if defined(ARDUINO_ARCH_SAMD)
+		/* for cortex m0, ldm and stm are restricted to low registers */
+		/* load high registers */
+		"add   r0, #16;"     /* they are 4 words higher in memory */
+		"ldmia r0, {r1-r6};" /* load them in low registers first... */
+		"mov   r8, r1;"      /* ...and move them into high registers... */
+		"mov   r9, r2;"
+		"mov   r10, r3;"
+		"mov   r11, r4;"
+		"mov   r12, r5;"
+		"mov   lr, r6;"
+		/* load low registers */
+		"sub   r0, r0, #40;" /* back to begin of context */
+		"ldmia r0, {r4-r7};"
+#else
 		"ldmia r0, {r4-r12, lr};"
+#endif
+		/* restore task stack */
 		"mov   sp, r12;"
+		/* resume task */
 		"bx    lr;"
 	);
 }
 
 static void __attribute__((naked)) __attribute__((noinline)) coopDoYield(CoopTask* curTask) {
 	asm (
 		"mov   r12, sp;"
-		"stmia r0, {r4-r12, lr};"
+		/* store low registers */
+		"stmia r0, {r4-r7};"
+		/* store high registers */
+		"mov   r1, r8;" /* move them to low registers first */
+		"mov   r2, r9;"
+		"mov   r3, r10;"
+		"mov   r4, r11;"
+		"mov   r5, r12;"
+		"mov   r6, lr;"
+		"stmia r0, {r1-r6};"
 		"mov   r0, #0;"
+		/* shedule. address of next task context is put in r0 */
 		"bl    coopSchedule;"
+#if defined(ARDUINO_ARCH_SAMD)
+		/* for cortex m0, ldm and stm are restricted to low registers */
+		/* load high registers */
+		"add   r0, #16;"     /* they are 4 words higher in memory */
+		"ldmia r0, {r1-r6};" /* load them in low registers first... */
+		"mov   r8, r1;"      /* ...and move them into high registers... */
+		"mov   r9, r2;"
+		"mov   r10, r3;"
+		"mov   r11, r4;"
+		"mov   r12, r5;"
+		"mov   lr, r6;"
+		/* load low registers */
+		"sub   r0, r0, #40;" /* back to begin of context */
+		"ldmia r0, {r4-r7};"
+#else
 		"ldmia r0, {r4-r12, lr};"
+#endif
+		/* restore task stack */
 		"mov   sp, r12;"
+		/* resume task */
 		"bx    lr;"
 	);
 }