diff --git a/serial_link/protocol/transport.h b/serial_link/protocol/transport.h
index 86086b8b..c4c52947 100644
--- a/serial_link/protocol/transport.h
+++ b/serial_link/protocol/transport.h
@@ -26,6 +26,7 @@ SOFTWARE.
 #define SERIAL_LINK_TRANSPORT_H
 
 #include "protocol/triple_buffered_object.h"
+#include "system/system.h"
 
 #define NUM_SLAVES 8
 #define LOCAL_OBJECT_EXTRA 16
@@ -65,7 +66,12 @@ typedef struct { \
             .object_type = MASTER_TO_ALL_SLAVES, \
             .object_size = sizeof(type), \
         } \
-    };
+    }; \
+    type* begin_write_##name(void) { \
+    }\
+    void end_write_##name(void) { \
+        signal_data_written(); \
+    }
 
 #define MASTER_TO_SINGLE_SLAVE_OBJECT(name, type) \
     REMOTE_OBJECT_HELPER(name, type, NUM_SLAVES, 1) \
@@ -74,7 +80,12 @@ typedef struct { \
             .object_type = MASTER_TO_SINGLE_SLAVE, \
             .object_size = sizeof(type), \
         } \
-    };
+    }; \
+    type* begin_write_##name(uint8_t slave) { \
+    }\
+    void end_write_##name(uint8_t slave) { \
+        signal_data_written(); \
+    }
 
 #define SLAVE_TO_MASTER_OBJECT(name, type) \
     REMOTE_OBJECT_HELPER(name, type, 1, NUM_SLAVES) \
@@ -83,7 +94,12 @@ typedef struct { \
             .object_type = SLAVE_TO_MASTER, \
             .object_size = sizeof(type), \
         } \
-    };
+    }; \
+    type* begin_write_##name(void) { \
+    }\
+    void end_write_##name(void) { \
+        signal_data_written(); \
+    }
 
 #define REMOTE_OBJECT(name) (remote_object_t*)&remote_object_##name
 
diff --git a/serial_link/system/system.h b/serial_link/system/system.h
index c798e647..16334995 100644
--- a/serial_link/system/system.h
+++ b/serial_link/system/system.h
@@ -26,11 +26,11 @@ SOFTWARE.
 #define SERIAL_LINK_SYSTEM_H
 
 void serial_link_lock() {
-
 }
 
 void serial_link_unlock() {
-
 }
 
+void signal_data_written(void);
+
 #endif
diff --git a/serial_link/tests/transport_tests.c b/serial_link/tests/transport_tests.c
index 31e7b2dc..61b9a650 100644
--- a/serial_link/tests/transport_tests.c
+++ b/serial_link/tests/transport_tests.c
@@ -23,8 +23,13 @@ SOFTWARE.
 */
 
 #include <cgreen/cgreen.h>
+#include <cgreen/mocks.h>
 #include "protocol/transport.c"
 
+void signal_data_written(void) {
+    mock();
+}
+
 typedef struct {
     uint32_t test;
 } test_object1_t;
@@ -51,4 +56,13 @@ BeforeEach(Transport) {
 AfterEach(Transport) {}
 
 Ensure(Transport, write_to_local_signals_an_event) {
+    begin_write_master_to_slave();
+    expect(signal_data_written);
+    end_write_master_to_slave();
+    begin_write_slave_to_master();
+    expect(signal_data_written);
+    end_write_slave_to_master();
+    begin_write_master_to_single_slave(1);
+    expect(signal_data_written);
+    end_write_master_to_single_slave(1);
 }