diff --git a/CMakeLists.txt b/CMakeLists.txt
index af86fb3..b61ebc1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,7 +24,7 @@ set(SOURCE_FILES
         gex/protocol/TinyFrame.c
         gex/protocol/TinyFrame.h
         gex/utils/type_coerce.h
-        gex/gex_defines.h gex/gex_unit.c gex/gex_unit.h)
+        gex/gex_defines.h gex/gex_unit.c gex/gex_unit.h gex/gex.h)
 
 include_directories(
         gex
diff --git a/gex/TF_Integration.c b/gex/TF_Integration.c
index 41a32d7..bb36bbf 100644
--- a/gex/TF_Integration.c
+++ b/gex/TF_Integration.c
@@ -5,6 +5,8 @@
 #include <errno.h>
 
 #include "TinyFrame.h"
+
+#define GEX_H // to allow including other headers
 #include "gex_internal.h"
 
 void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, size_t len)
diff --git a/gex/gex.h b/gex/gex.h
new file mode 100644
index 0000000..b76ff06
--- /dev/null
+++ b/gex/gex.h
@@ -0,0 +1,13 @@
+//
+// Created by MightyPork on 2017/12/19.
+//
+
+#ifndef GEX_H
+#define GEX_H
+
+#include "gex_defines.h"
+#include "gex_client.h"
+#include "gex_unit.h"
+#include "gex_message_types.h"
+
+#endif //GEX_H
diff --git a/gex/gex_client.c b/gex/gex_client.c
index 241800b..c4c9fba 100644
--- a/gex/gex_client.c
+++ b/gex/gex_client.c
@@ -10,6 +10,7 @@
 #include <errno.h>
 #include "TinyFrame.h"
 
+#define GEX_H // to allow including other headers
 #include "gex_client.h"
 #include "serial.h"
 #include "gex_internal.h"
@@ -53,7 +54,7 @@ static TF_Result unit_report_lst(TinyFrame *tf, TF_Msg *msg)
         .payload = (uint8_t *) (msg->data + 2),
         .len = (uint32_t) (msg->len - 2),
         .type = rpt_type,
-        .unit = (lu == NULL) ? fbu : lu,
+        .unit = (lu == NULL) ? &fbu : lu,
     };
 
     if (lu && lu->report_handler) {
@@ -85,9 +86,10 @@ static TF_Result list_units_lst(TinyFrame *tf, TF_Msg *msg)
         // append
         struct gex_unit *lu = malloc(sizeof(struct gex_unit));
         lu->next = NULL;
-        lu->type = "UNKNOWN";
+        lu->type = strdup("UNKNOWN"); // TODO
         lu->name = strdup(buf);
         lu->callsign = callsign;
+        lu->gex = gex;
         lu->report_handler = NULL;
         if (tail == NULL) {
             gex->ulu_head = lu;
@@ -111,6 +113,12 @@ void GEX_OnReport(GexClient *gex, GexUnit *unit, GexEventListener lst)
     }
 }
 
+/** Find a unit */
+GexUnit *GEX_Unit(GexClient *gex, const char *name)
+{
+    return gex_find_unit_by_name(gex, name);
+}
+
 /** Create a instance and connect */
 GexClient *GEX_Init(const char *device, int timeout_ms)
 {
@@ -125,6 +133,7 @@ GexClient *GEX_Init(const char *device, int timeout_ms)
     gex->acm_fd = serial_open(device, false, (timeout_ms + 50) / 100);
     if (gex->acm_fd == -1) {
         free(gex);
+        fprintf(stderr, "FAILED TO CONNECT TO %s!\n", device);
         return NULL;
     }
 
@@ -172,7 +181,7 @@ void GEX_Poll(GexClient *gex)
 void GEX_DeInit(GexClient *gex)
 {
     if (gex == NULL) return;
-    close(gex->acm_fd);
+    fsync(gex->acm_fd);
     gex_destroy_unit_lookup(gex);
     TF_DeInit(gex->tf);
     free(gex);
diff --git a/gex/gex_client.h b/gex/gex_client.h
index f32a9a0..83ec77a 100644
--- a/gex/gex_client.h
+++ b/gex/gex_client.h
@@ -5,6 +5,10 @@
 #ifndef GEX_CLIENT_GEX_CLIENT_H
 #define GEX_CLIENT_GEX_CLIENT_H
 
+#ifndef GEX_H
+#error "Include gex.h instead!"
+#endif
+
 #include <stddef.h>
 #include <stdint.h>
 #include <stdbool.h>
@@ -22,6 +26,14 @@
  */
 void GEX_OnReport(GexClient *gex, GexUnit *unit, GexEventListener lst);
 
+/**
+ * Get a unit, or NULL
+ *
+ * @param gex - gex
+ * @param name - unit name
+ */
+GexUnit *GEX_Unit(GexClient *gex, const char *name);
+
 /**
  * Initialize the GEX client
  *
diff --git a/gex/gex_defines.h b/gex/gex_defines.h
index 8b617ed..d544713 100644
--- a/gex/gex_defines.h
+++ b/gex/gex_defines.h
@@ -5,9 +5,15 @@
 #ifndef GEX_CLIENT_GEX_DEFINES_H
 #define GEX_CLIENT_GEX_DEFINES_H
 
+#ifndef GEX_H
+#error "Include gex.h instead!"
+#endif
+
 #include <stdint.h>
 #include <stdbool.h>
 
+#include "TinyFrame.h"
+
 typedef TF_ID GexSession;
 
 typedef struct gex_client GexClient;
diff --git a/gex/gex_helpers.c b/gex/gex_helpers.c
index 560ea60..738c2a0 100644
--- a/gex/gex_helpers.c
+++ b/gex/gex_helpers.c
@@ -3,17 +3,23 @@
 //
 
 #include <malloc.h>
+#include <assert.h>
 
+#define GEX_H // to allow including other headers
 #include "gex_defines.h"
 #include "gex_helpers.h"
 
 /** Delete recursively all GEX callsign look-up table entries */
 void gex_destroy_unit_lookup(GexClient *gex)
 {
+    assert(gex != NULL);
+
     struct gex_unit *next = gex->ulu_head;
     while (next != NULL) {
         struct gex_unit *cur = next;
         next = next->next;
+        free(cur->name);
+        free(cur->type);
         free(cur);
     }
     gex->ulu_head = NULL;
@@ -22,6 +28,8 @@ void gex_destroy_unit_lookup(GexClient *gex)
 /** Get lookup entry for unit name */
 struct gex_unit *gex_find_unit_by_callsign(GexClient *gex, uint8_t callsign)
 {
+    assert(gex != NULL);
+
     struct gex_unit *next = gex->ulu_head;
     while (next != NULL) {
         if (next->callsign == callsign) {
@@ -35,6 +43,9 @@ struct gex_unit *gex_find_unit_by_callsign(GexClient *gex, uint8_t callsign)
 /** Get lookup entry for unit name */
 struct gex_unit *gex_find_unit_by_name(GexClient *gex, const char *name)
 {
+    assert(gex != NULL);
+    assert(name != NULL);
+
     struct gex_unit *next = gex->ulu_head;
     while (next != NULL) {
         if (strcmp(next->name, name) == 0) {
@@ -48,6 +59,8 @@ struct gex_unit *gex_find_unit_by_name(GexClient *gex, const char *name)
 /** Get callsign for unit name */
 uint8_t gex_find_callsign_by_name(GexClient *gex, const char *name)
 {
+    assert(gex != NULL);
+
     struct gex_unit *lu = gex_find_unit_by_name(gex, name);
     return (uint8_t) ((lu == NULL) ? 0 : lu->callsign);
 }
diff --git a/gex/gex_helpers.h b/gex/gex_helpers.h
index f138ee1..5d9892a 100644
--- a/gex/gex_helpers.h
+++ b/gex/gex_helpers.h
@@ -5,6 +5,10 @@
 #ifndef GEX_CLIENT_GEX_HELPERS_H
 #define GEX_CLIENT_GEX_HELPERS_H
 
+#ifndef GEX_H
+#error "Include gex.h instead!"
+#endif
+
 #include "gex_internal.h"
 #include "gex_defines.h"
 
diff --git a/gex/gex_message_types.h b/gex/gex_message_types.h
index 2e2a60e..9c2cb60 100644
--- a/gex/gex_message_types.h
+++ b/gex/gex_message_types.h
@@ -5,6 +5,10 @@
 #ifndef GEX_CLIENT_GEX_MESSAGE_TYPES_H
 #define GEX_CLIENT_GEX_MESSAGE_TYPES_H
 
+#ifndef GEX_H
+#error "Include gex.h instead!"
+#endif
+
 /**
  * Supported message types (TF_TYPE)
  */
diff --git a/gex/gex_unit.c b/gex/gex_unit.c
index 6b29619..adf8b8c 100644
--- a/gex/gex_unit.c
+++ b/gex/gex_unit.c
@@ -4,6 +4,8 @@
 
 #include <malloc.h>
 #include <assert.h>
+
+#define GEX_H // to allow including other headers
 #include "gex_defines.h"
 #include "gex_helpers.h"
 #include "gex_message_types.h"
@@ -20,9 +22,12 @@
  */
 static void GEX_LL_Query(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len, TF_Listener lst, void *userdata2)
 {
+    assert(unit != NULL);
+    assert(unit->gex != NULL);
+
     GexClient *gex = unit->gex;
 
-    uint8_t callsign = gex_find_callsign_by_name(gex, unit);
+    uint8_t callsign = unit->callsign;
     assert(callsign != 0);
     uint8_t *pld = malloc(len + 2);
     assert(pld != NULL);
@@ -48,6 +53,9 @@ static void GEX_LL_Query(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t
 /** Send with no listener, don't wait for response */
 void GEX_Send(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len)
 {
+    assert(unit != NULL);
+    assert(unit->gex != NULL);
+
     GEX_LL_Query(unit, cmd, payload, len, NULL, NULL);
 }
 
@@ -55,6 +63,8 @@ void GEX_Send(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len)
 static TF_Result sync_query_lst(TinyFrame *tf, TF_Msg *msg)
 {
     GexClient *gex = tf->userdata;
+    assert(gex != NULL);
+
     // clone the message
     gex->sync_query_response.len = msg->len;
     gex->sync_query_response.session = msg->frame_id;
@@ -70,7 +80,11 @@ static TF_Result sync_query_lst(TinyFrame *tf, TF_Msg *msg)
 /** Static query */
 GexMsg GEX_Query(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len)
 {
+    assert(unit != NULL);
+    assert(unit->gex != NULL);
+
     GexClient *gex = unit->gex;
+
     gex->sync_query_ok = false;
 
     // Default response that will be used if nothing is received
@@ -113,6 +127,9 @@ static TF_Result async_query_lst(TinyFrame *tf, TF_Msg *msg)
 /** Sync query, without poll */
 void GEX_QueryAsync(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len, GexEventListener lst)
 {
+    assert(unit != NULL);
+    assert(unit->gex != NULL);
+
     GexClient *gex = unit->gex;
     gex->sync_query_ok = false;
     memset(&gex->sync_query_response, 0, sizeof(GexMsg));
diff --git a/gex/gex_unit.h b/gex/gex_unit.h
index 1463320..073fccc 100644
--- a/gex/gex_unit.h
+++ b/gex/gex_unit.h
@@ -5,6 +5,22 @@
 #ifndef GEX_CLIENT_GEX_UNIT_H
 #define GEX_CLIENT_GEX_UNIT_H
 
+#ifndef GEX_H
+#error "Include gex.h instead!"
+#endif
+
+#include "gex_defines.h"
+#include <stdint.h>
+#include <stdbool.h>
+
+/** Send with no listener, don't wait for response */
+void GEX_Send(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len);
+
+/** Static query */
+GexMsg GEX_Query(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len);
+
+/** Sync query, without poll */
+void GEX_QueryAsync(GexUnit *unit, uint8_t cmd, uint8_t *payload, uint32_t len, GexEventListener lst);
 
 
 #endif //GEX_CLIENT_GEX_UNIT_H
diff --git a/main.c b/main.c
index bf81c32..e6d998a 100644
--- a/main.c
+++ b/main.c
@@ -1,7 +1,9 @@
 #include <stdio.h>
 #include <stdlib.h>
-#include "gex_client.h"
 #include <signal.h>
+#include <assert.h>
+
+#include "gex.h"
 
 static GexClient *gex;
 
@@ -14,18 +16,20 @@ static void sigintHandler(int sig)
     exit(0);
 }
 
+#define LED_CMD_TOGGLE 0x02
+
 int main()
 {
     // Bind ^C handler for safe shutdown
     signal(SIGINT, sigintHandler);
 
 	gex = GEX_Init("/dev/ttyACM0", 200);
-	if (!gex) {
-		fprintf(stderr, "FAILED TO CONNECT, ABORTING!\n");
-		exit(1);
-	}
+	if (!gex) exit(1);
+
+    GexUnit *led = GEX_Unit(gex, "LED");
+    assert(led != NULL);
 
-	printf("Hello, World!\n");
+    GEX_Send(led, LED_CMD_TOGGLE, NULL, 0);
 
 	GEX_DeInit(gex);
 	return 0;