diff --git a/platforms/qemu_integratorcp/Makefile b/platforms/qemu_integratorcp/Makefile
index e88e47d..cc54f51 100644
--- a/platforms/qemu_integratorcp/Makefile
+++ b/platforms/qemu_integratorcp/Makefile
@@ -44,7 +44,7 @@ include 	../rules.mk
 
 run_test: clean all
 	echo "START TEST $(TEST_NAME)"
-	qemu-system-arm -M integratorcp -kernel boot.elf  -semihosting | tee atomthreads_test.out
+	qemu-system-arm -M integratorcp -kernel boot.elf  -semihosting >> atomthreads_test.out
 
 all_tests:
 	echo "Starting atomthreads test suite" > atomthreads_test.out
@@ -87,5 +87,5 @@ all_tests:
 	make run_test "TEST_NAME=sem9"
 
 run_last:
-	qemu-system-arm -M integratorcp -kernel boot.elf   -monitor stdio -semihosting
+	qemu-system-arm -M integratorcp -kernel boot.elf -semihosting
 
diff --git a/platforms/qemu_integratorcp/main.c b/platforms/qemu_integratorcp/main.c
index 3222170..aebdd3d 100644
--- a/platforms/qemu_integratorcp/main.c
+++ b/platforms/qemu_integratorcp/main.c
@@ -77,8 +77,8 @@ main (void)
 
     printf ("atomthreads starting %s... ", ATOMTHREADS_TEST) ;
 
-	atomOSInit(&idle_stack[IDLE_STACK_BYTE_SIZE - sizeof(unsigned int)], IDLE_STACK_BYTE_SIZE - sizeof(unsigned int)) ;
-    atomThreadCreate ((ATOM_TCB *)&test_tcb, TEST_THREAD_PRIO, test_thread, 0, &test_stack[(TEST_STACK_BYTE_SIZE) - sizeof(unsigned int)], TEST_STACK_BYTE_SIZE  - sizeof(unsigned int));
+    atomOSInit(&idle_stack[0], IDLE_STACK_BYTE_SIZE, TRUE) ;
+    atomThreadCreate ((ATOM_TCB *)&test_tcb, TEST_THREAD_PRIO, test_thread, 0, &test_stack[0], TEST_STACK_BYTE_SIZE, TRUE);
     atomOSStart() ;
 
     return 0 ;
diff --git a/platforms/qemu_lm3s/Makefile b/platforms/qemu_lm3s/Makefile
index c8568ad..dc9c117 100644
--- a/platforms/qemu_lm3s/Makefile
+++ b/platforms/qemu_lm3s/Makefile
@@ -85,11 +85,11 @@ all_tests:
 	make run_test "TEST_NAME=sem8"
 	make run_test "TEST_NAME=sem9"
 
-all_fail:
+fail_tests:
 		make run_test "TEST_NAME=mutex4"
 		make run_test "TEST_NAME=sem4"
 
 
 run_last:
-	qemu-system-arm -M lm3s6965evb -kernel boot.elf  -monitor stdio -semihosting
+	qemu-system-arm -M lm3s6965evb -kernel boot.elf  -semihosting
 
diff --git a/platforms/qemu_lm3s/main.c b/platforms/qemu_lm3s/main.c
index 9aa5bdc..725a642 100644
--- a/platforms/qemu_lm3s/main.c
+++ b/platforms/qemu_lm3s/main.c
@@ -79,8 +79,8 @@ main (void)
     uint32_t failures ;
     printf ("Atomthreads starting %s... \r\n", ATOMTHREADS_TEST) ;
 
-    atomOSInit(&idle_stack[IDLE_STACK_BYTE_SIZE - sizeof(unsigned int)], IDLE_STACK_BYTE_SIZE - sizeof(unsigned int)) ;
-    atomThreadCreate ((ATOM_TCB *)&test_tcb, TEST_THREAD_PRIO, test_thread, 0, &test_stack[(TEST_STACK_BYTE_SIZE) - sizeof(unsigned int)], TEST_STACK_BYTE_SIZE  - sizeof(unsigned int));
+    atomOSInit(&idle_stack[0], IDLE_STACK_BYTE_SIZE, TRUE) ;
+    atomThreadCreate ((ATOM_TCB *)&test_tcb, TEST_THREAD_PRIO, test_thread, 0, &test_stack[0], TEST_STACK_BYTE_SIZE, TRUE);
     atomOSStart() ;
 
     return 0 ;
diff --git a/ports/arm/atomport.h b/ports/arm/atomport.h
index f7ac10d..f07e75a 100644
--- a/ports/arm/atomport.h
+++ b/ports/arm/atomport.h
@@ -32,8 +32,17 @@
 
 #include "types.h"
 
-#define SYSTEM_TICKS_PER_SEC            100
+#define SYSTEM_TICKS_PER_SEC    100
 
+/**
+ * Definition of NULL.
+ * If stddef.h is available on the platform it is simplest to include it
+ * from this header, otherwise define below.
+ */
+#define NULL					((void *)(0))
+
+/* Size of each stack entry / stack alignment size (e.g. 32 bits) */
+#define STACK_ALIGN_SIZE        sizeof(unsigned int)
 
 /**
  * Architecture-specific types.
@@ -47,12 +56,17 @@
  * Functions defined in atomport_arm.asm
  *
  */
-extern void             contextInit (void) ;
-extern uint32_t         contextEnterCritical (void) ;
-extern void             contextExitCritical (uint32_t posture) ;
+extern void						contextInit (void) ;
+extern uint32_t					contextEnterCritical (void) ;
+extern void						contextExitCritical (uint32_t posture) ;
 
 
-/* Critical region protection */
+/**
+ * Critical region protection: this should disable interrupts
+ * to protect OS data structures during modification. It must
+ * allow nested calls, which means that interrupts should only
+ * be re-enabled when the outer CRITICAL_END() is reached.
+ */
 #define CRITICAL_STORE          uint32_t __atom_critical
 #define CRITICAL_START()        __atom_critical = contextEnterCritical()
 #define CRITICAL_END()          contextExitCritical(__atom_critical)
diff --git a/ports/cortex_m/atomport.h b/ports/cortex_m/atomport.h
index f7ac10d..1a4cfd9 100644
--- a/ports/cortex_m/atomport.h
+++ b/ports/cortex_m/atomport.h
@@ -32,7 +32,23 @@
 
 #include "types.h"
 
-#define SYSTEM_TICKS_PER_SEC            100
+#define SYSTEM_TICKS_PER_SEC    100
+
+/**
+ * Definition of NULL.
+ * If stddef.h is available on the platform it is simplest to include it
+ * from this header, otherwise define below.
+ */
+#define NULL					((void *)(0))
+
+/* Size of each stack entry / stack alignment size (e.g. 32 bits) */
+#define STACK_ALIGN_SIZE        sizeof(unsigned int)
+
+/**
+ * Architecture-specific types.
+ * Most of these are available from types.h on this platform, which is
+ * included above.
+ */
 
 
 /**
@@ -47,9 +63,9 @@
  * Functions defined in atomport_arm.asm
  *
  */
-extern void             contextInit (void) ;
-extern uint32_t         contextEnterCritical (void) ;
-extern void             contextExitCritical (uint32_t posture) ;
+extern void						contextInit (void) ;
+extern uint32_t					contextEnterCritical (void) ;
+extern void						contextExitCritical (uint32_t posture) ;
 
 
 /* Critical region protection */
@@ -58,3 +74,4 @@ extern void             contextExitCritical (uint32_t posture) ;
 #define CRITICAL_END()          contextExitCritical(__atom_critical)
 
 #endif /* __ATOM_PORT_H__ */
+