diff --git a/libraries/AP_HAL/examples/BinarySem/BinarySem.cpp b/libraries/AP_HAL/examples/BinarySem/BinarySem.cpp
new file mode 100644
index 0000000000..885933ded9
--- /dev/null
+++ b/libraries/AP_HAL/examples/BinarySem/BinarySem.cpp
@@ -0,0 +1,91 @@
+/*
+  test of HAL_BinarySemaphore
+ */
+
+#include <AP_HAL/AP_HAL.h>
+#include <AP_HAL/Semaphores.h>
+
+#include <stdio.h>
+
+void setup();
+void loop();
+
+const AP_HAL::HAL& hal = AP_HAL::get_HAL();
+
+class BinarySemTest {
+public:
+    HAL_BinarySemaphore sem1{1};
+    HAL_BinarySemaphore sem2{0};
+
+    void setup(void);
+    void thread1(void);
+    void thread2(void);
+    void update(bool ok);
+
+    uint32_t ops, timeouts;
+    uint32_t last_print_us;
+    HAL_Semaphore mtx;
+};
+
+void BinarySemTest::setup(void)
+{
+    hal.scheduler->thread_create(
+        FUNCTOR_BIND_MEMBER(&BinarySemTest::thread1, void), "thd1", 2048, AP_HAL::Scheduler::PRIORITY_IO, 0);
+    hal.scheduler->thread_create(
+        FUNCTOR_BIND_MEMBER(&BinarySemTest::thread2, void), "thd2", 2048, AP_HAL::Scheduler::PRIORITY_IO, 0);
+    ::printf("Setup threads\n");
+}
+
+void BinarySemTest::thread2(void)
+{
+    while (true) {
+        bool ok = sem2.wait(50000);
+        sem1.signal();
+        update(ok);
+    }
+}
+
+void BinarySemTest::thread1(void)
+{
+    while (true) {
+        bool ok = sem1.wait(50000);
+        sem2.signal();
+        update(ok);
+    }
+}
+
+void BinarySemTest::update(bool ok)
+{
+    WITH_SEMAPHORE(mtx);
+    if (ok) {
+        ops++;
+    } else {
+        timeouts++;
+    }
+    uint32_t now_us = AP_HAL::micros();
+    float dt = (now_us - last_print_us)*1.0e-6;
+    if (dt >= 1.0) {
+        last_print_us = now_us;
+        ::printf("tick %u %.3f ops/s %.3f timeouts/s\n",
+                 unsigned(AP_HAL::millis()),
+                 ops/dt,
+                 timeouts/dt);
+        ops = 0;
+        timeouts = 0;
+    }
+}
+
+static BinarySemTest *ct;
+
+void setup(void)
+{
+    ct = new BinarySemTest;
+    ct->setup();
+}
+
+void loop(void)
+{
+    hal.scheduler->delay(1000);
+}
+
+AP_HAL_MAIN();
diff --git a/libraries/AP_HAL/examples/BinarySem/wscript b/libraries/AP_HAL/examples/BinarySem/wscript
new file mode 100644
index 0000000000..719ec151ba
--- /dev/null
+++ b/libraries/AP_HAL/examples/BinarySem/wscript
@@ -0,0 +1,7 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+def build(bld):
+    bld.ap_example(
+        use='ap',
+    )