diff --git a/flight/pios/common/pios_com.c b/flight/pios/common/pios_com.c
index 9a4b83f60..db7d85f60 100644
--- a/flight/pios/common/pios_com.c
+++ b/flight/pios/common/pios_com.c
@@ -338,7 +338,7 @@ static int32_t PIOS_COM_SendBufferNonBlockingInternal(struct pios_com_dev *com_d
 {
     PIOS_Assert(com_dev);
     PIOS_Assert(com_dev->has_tx);
-    if (com_dev->driver->available && !com_dev->driver->available(com_dev->lower_id)) {
+    if (com_dev->driver->available && !(com_dev->driver->available(com_dev->lower_id) & COM_AVAILABLE_TX)) {
         /*
          * Underlying device is down/unconnected.
          * Dump our fifo contents and act like an infinite data sink.
@@ -625,18 +625,26 @@ check_again:
  * used to check a link is established even if the device
  * is valid.
  */
-bool PIOS_COM_Available(uint32_t com_id)
+uint32_t PIOS_COM_Available(uint32_t com_id)
 {
     struct pios_com_dev *com_dev = (struct pios_com_dev *)com_id;
 
     if (!PIOS_COM_validate(com_dev)) {
-        return false;
+        return COM_AVAILABLE_NONE;
     }
 
     // If a driver does not provide a query method assume always
     // available if valid
     if (com_dev->driver->available == NULL) {
-        return true;
+        if (com_dev->has_rx && com_dev->has_tx) {
+            return COM_AVAILABLE_RXTX;
+        } else if (com_dev->has_rx) {
+            return COM_AVAILABLE_RX;
+        } else if (com_dev->has_tx) {
+            return COM_AVAILABLE_TX;
+        }
+
+        return COM_AVAILABLE_NONE; /* can this really happen? */
     }
 
     return (com_dev->driver->available)(com_dev->lower_id);
diff --git a/flight/pios/common/pios_rfm22b_com.c b/flight/pios/common/pios_rfm22b_com.c
index 964cee585..1669e1095 100644
--- a/flight/pios/common/pios_rfm22b_com.c
+++ b/flight/pios/common/pios_rfm22b_com.c
@@ -40,7 +40,7 @@ static void PIOS_RFM22B_COM_RegisterRxCallback(uint32_t rfm22b_id, pios_com_call
 static void PIOS_RFM22B_COM_RegisterTxCallback(uint32_t rfm22b_id, pios_com_callback tx_out_cb, uint32_t context);
 static void PIOS_RFM22B_COM_TxStart(uint32_t rfm22b_id, uint16_t tx_bytes_avail);
 static void PIOS_RFM22B_COM_RxStart(uint32_t rfm22b_id, uint16_t rx_bytes_avail);
-static bool PIOS_RFM22B_COM_Available(uint32_t rfm22b_com_id);
+static uint32_t PIOS_RFM22B_COM_Available(uint32_t rfm22b_com_id);
 
 /* Local variables */
 const struct pios_com_driver pios_rfm22b_com_driver = {
@@ -135,9 +135,9 @@ static void PIOS_RFM22B_COM_RegisterTxCallback(uint32_t rfm22b_id, pios_com_call
  * @param[in] rfm22b_dev  The device ID.
  * @return True of the device is available.
  */
-static bool PIOS_RFM22B_COM_Available(uint32_t rfm22b_id)
+static uint32_t PIOS_RFM22B_COM_Available(uint32_t rfm22b_id)
 {
-    return PIOS_RFM22B_LinkStatus(rfm22b_id);
+    return PIOS_RFM22B_LinkStatus(rfm22b_id) ? COM_AVAILABLE_RXTX : COM_AVAILABLE_NONE;
 }
 
 #endif /* PIOS_INCLUDE_RFM22B_COM */
diff --git a/flight/pios/inc/pios_com.h b/flight/pios/inc/pios_com.h
index b2591e4f0..cf209c2ba 100644
--- a/flight/pios/inc/pios_com.h
+++ b/flight/pios/inc/pios_com.h
@@ -39,15 +39,15 @@ typedef uint16_t (*pios_com_callback)(uint32_t context, uint8_t *buf, uint16_t b
 typedef void (*pios_com_callback_ctrl_line)(uint32_t context, uint32_t mask, uint32_t state);
 
 struct pios_com_driver {
-    void (*init)(uint32_t id);
-    void (*set_baud)(uint32_t id, uint32_t baud);
-    void (*set_ctrl_line)(uint32_t id, uint32_t mask, uint32_t state);
-    void (*tx_start)(uint32_t id, uint16_t tx_bytes_avail);
-    void (*rx_start)(uint32_t id, uint16_t rx_bytes_avail);
-    void (*bind_rx_cb)(uint32_t id, pios_com_callback rx_in_cb, uint32_t context);
-    void (*bind_tx_cb)(uint32_t id, pios_com_callback tx_out_cb, uint32_t context);
-    void (*bind_ctrl_line_cb)(uint32_t id, pios_com_callback_ctrl_line ctrl_line_cb, uint32_t context);
-    bool (*available)(uint32_t id);
+    void     (*init)(uint32_t id);
+    void     (*set_baud)(uint32_t id, uint32_t baud);
+    void     (*set_ctrl_line)(uint32_t id, uint32_t mask, uint32_t state);
+    void     (*tx_start)(uint32_t id, uint16_t tx_bytes_avail);
+    void     (*rx_start)(uint32_t id, uint16_t rx_bytes_avail);
+    void     (*bind_rx_cb)(uint32_t id, pios_com_callback rx_in_cb, uint32_t context);
+    void     (*bind_tx_cb)(uint32_t id, pios_com_callback tx_out_cb, uint32_t context);
+    void     (*bind_ctrl_line_cb)(uint32_t id, pios_com_callback_ctrl_line ctrl_line_cb, uint32_t context);
+    uint32_t (*available)(uint32_t id);
 };
 
 /* Control line definitions */
@@ -68,7 +68,12 @@ extern int32_t PIOS_COM_SendString(uint32_t com_id, const char *str);
 extern int32_t PIOS_COM_SendFormattedStringNonBlocking(uint32_t com_id, const char *format, ...);
 extern int32_t PIOS_COM_SendFormattedString(uint32_t com_id, const char *format, ...);
 extern uint16_t PIOS_COM_ReceiveBuffer(uint32_t com_id, uint8_t *buf, uint16_t buf_len, uint32_t timeout_ms);
-extern bool PIOS_COM_Available(uint32_t com_id);
+extern uint32_t PIOS_COM_Available(uint32_t com_id);
+
+#define COM_AVAILABLE_NONE (0)
+#define COM_AVAILABLE_RX   (1 << 0)
+#define COM_AVAILABLE_TX   (1 << 1)
+#define COM_AVAILABLE_RXTX (COM_AVAILABLE_RX | COM_AVAILABLE_TX)
 
 #endif /* PIOS_COM_H */
 
diff --git a/flight/pios/osx/inc/pios_com.h b/flight/pios/osx/inc/pios_com.h
index edac1e181..e10247bd4 100644
--- a/flight/pios/osx/inc/pios_com.h
+++ b/flight/pios/osx/inc/pios_com.h
@@ -35,13 +35,13 @@
 typedef uint16_t (*pios_com_callback)(uint32_t context, uint8_t *buf, uint16_t buf_len, uint16_t *headroom, bool *task_woken);
 
 struct pios_com_driver {
-    void (*init)(uint32_t id);
-    void (*set_baud)(uint32_t id, uint32_t baud);
-    void (*tx_start)(uint32_t id, uint16_t tx_bytes_avail);
-    void (*rx_start)(uint32_t id, uint16_t rx_bytes_avail);
-    void (*bind_rx_cb)(uint32_t id, pios_com_callback rx_in_cb, uint32_t context);
-    void (*bind_tx_cb)(uint32_t id, pios_com_callback tx_out_cb, uint32_t context);
-    bool (*available)(uint32_t id);
+    void     (*init)(uint32_t id);
+    void     (*set_baud)(uint32_t id, uint32_t baud);
+    void     (*tx_start)(uint32_t id, uint16_t tx_bytes_avail);
+    void     (*rx_start)(uint32_t id, uint16_t rx_bytes_avail);
+    void     (*bind_rx_cb)(uint32_t id, pios_com_callback rx_in_cb, uint32_t context);
+    void     (*bind_tx_cb)(uint32_t id, pios_com_callback tx_out_cb, uint32_t context);
+    uint32_t (*available)(uint32_t id);
 };
 
 /* Public Functions */
@@ -56,7 +56,12 @@ extern int32_t PIOS_COM_SendString(uint32_t com_id, const char *str);
 extern int32_t PIOS_COM_SendFormattedStringNonBlocking(uint32_t com_id, const char *format, ...);
 extern int32_t PIOS_COM_SendFormattedString(uint32_t com_id, const char *format, ...);
 extern uint16_t PIOS_COM_ReceiveBuffer(uint32_t com_id, uint8_t *buf, uint16_t buf_len, uint32_t timeout_ms);
-extern bool PIOS_COM_Available(uint32_t com_id);
+extern uint32_t PIOS_COM_Available(uint32_t com_id);
+
+#define COM_AVAILABLE_NONE (0)
+#define COM_AVAILABLE_RX   (1 << 0)
+#define COM_AVAILABLE_TX   (1 << 1)
+#define COM_AVAILABLE_RXTX (COM_AVAILABLE_RX | COM_AVAILABLE_TX)
 
 #endif /* PIOS_COM_H */
 
diff --git a/flight/pios/osx/osx/pios_com.c b/flight/pios/osx/osx/pios_com.c
index 8eab84a4e..8cd754055 100644
--- a/flight/pios/osx/osx/pios_com.c
+++ b/flight/pios/osx/osx/pios_com.c
@@ -509,18 +509,26 @@ check_again:
  * used to check a link is established even if the device
  * is valid.
  */
-bool PIOS_COM_Available(uint32_t com_id)
+uint32_t PIOS_COM_Available(uint32_t com_id)
 {
     struct pios_com_dev *com_dev = PIOS_COM_find_dev(com_id);
 
     if (!PIOS_COM_validate(com_dev)) {
-        return false;
+        return COM_AVAILABLE_NONE;
     }
 
     // If a driver does not provide a query method assume always
     // available if valid
     if (com_dev->driver->available == NULL) {
-        return true;
+        if (com_dev->has_rx && com_dev->has_tx) {
+            return COM_AVAILABLE_RXTX;
+        } else if (com_dev->has_rx) {
+            return COM_AVAILABLE_RX;
+        } else if (com_dev->has_tx) {
+            return COM_AVAILABLE_TX;
+        }
+
+        return COM_AVAILABLE_NONE; /* can this really happen? */
     }
 
     return (com_dev->driver->available)(com_dev->lower_id);
diff --git a/flight/pios/posix/pios_com.c b/flight/pios/posix/pios_com.c
index 8eab84a4e..8cd754055 100644
--- a/flight/pios/posix/pios_com.c
+++ b/flight/pios/posix/pios_com.c
@@ -509,18 +509,26 @@ check_again:
  * used to check a link is established even if the device
  * is valid.
  */
-bool PIOS_COM_Available(uint32_t com_id)
+uint32_t PIOS_COM_Available(uint32_t com_id)
 {
     struct pios_com_dev *com_dev = PIOS_COM_find_dev(com_id);
 
     if (!PIOS_COM_validate(com_dev)) {
-        return false;
+        return COM_AVAILABLE_NONE;
     }
 
     // If a driver does not provide a query method assume always
     // available if valid
     if (com_dev->driver->available == NULL) {
-        return true;
+        if (com_dev->has_rx && com_dev->has_tx) {
+            return COM_AVAILABLE_RXTX;
+        } else if (com_dev->has_rx) {
+            return COM_AVAILABLE_RX;
+        } else if (com_dev->has_tx) {
+            return COM_AVAILABLE_TX;
+        }
+
+        return COM_AVAILABLE_NONE; /* can this really happen? */
     }
 
     return (com_dev->driver->available)(com_dev->lower_id);
diff --git a/flight/pios/stm32f10x/pios_usb_cdc.c b/flight/pios/stm32f10x/pios_usb_cdc.c
index e7c3c1fda..4b45cbeff 100644
--- a/flight/pios/stm32f10x/pios_usb_cdc.c
+++ b/flight/pios/stm32f10x/pios_usb_cdc.c
@@ -43,7 +43,7 @@ static void PIOS_USB_CDC_RegisterTxCallback(uint32_t usbcdc_id, pios_com_callbac
 static void PIOS_USB_CDC_RegisterRxCallback(uint32_t usbcdc_id, pios_com_callback rx_in_cb, uint32_t context);
 static void PIOS_USB_CDC_TxStart(uint32_t usbcdc_id, uint16_t tx_bytes_avail);
 static void PIOS_USB_CDC_RxStart(uint32_t usbcdc_id, uint16_t rx_bytes_avail);
-static bool PIOS_USB_CDC_Available(uint32_t usbcdc_id);
+static uint32_t PIOS_USB_CDC_Available(uint32_t usbcdc_id);
 
 const struct pios_com_driver pios_usb_cdc_com_driver = {
     .tx_start   = PIOS_USB_CDC_TxStart,
@@ -353,7 +353,7 @@ RESULT PIOS_USB_CDC_SetControlLineState(void)
     return USB_SUCCESS;
 }
 
-static bool PIOS_USB_CDC_Available(uint32_t usbcdc_id)
+static uint32_t PIOS_USB_CDC_Available(uint32_t usbcdc_id)
 {
     struct pios_usb_cdc_dev *usb_cdc_dev = (struct pios_usb_cdc_dev *)usbcdc_id;
 
@@ -361,8 +361,8 @@ static bool PIOS_USB_CDC_Available(uint32_t usbcdc_id)
 
     PIOS_Assert(valid);
 
-    return PIOS_USB_CheckAvailable(usb_cdc_dev->lower_id) &&
-           (control_line_state & USB_CDC_CONTROL_LINE_STATE_DTE_PRESENT);
+    return (PIOS_USB_CheckAvailable(usb_cdc_dev->lower_id) &&
+            (control_line_state & USB_CDC_CONTROL_LINE_STATE_DTE_PRESENT)) ? COM_AVAILABLE_RXTX : COM_AVAILABLE_NONE;
 }
 
 static struct usb_cdc_line_coding line_coding = {
diff --git a/flight/pios/stm32f10x/pios_usb_hid.c b/flight/pios/stm32f10x/pios_usb_hid.c
index 532a78a7c..6b1e9d81b 100644
--- a/flight/pios/stm32f10x/pios_usb_hid.c
+++ b/flight/pios/stm32f10x/pios_usb_hid.c
@@ -43,13 +43,14 @@ static void PIOS_USB_HID_RegisterTxCallback(uint32_t usbhid_id, pios_com_callbac
 static void PIOS_USB_HID_RegisterRxCallback(uint32_t usbhid_id, pios_com_callback rx_in_cb, uint32_t context);
 static void PIOS_USB_HID_TxStart(uint32_t usbhid_id, uint16_t tx_bytes_avail);
 static void PIOS_USB_HID_RxStart(uint32_t usbhid_id, uint16_t rx_bytes_avail);
+static uint32_t PIOS_USB_HID_Available(uint32_t usbhid_id);
 
 const struct pios_com_driver pios_usb_hid_com_driver = {
     .tx_start   = PIOS_USB_HID_TxStart,
     .rx_start   = PIOS_USB_HID_RxStart,
     .bind_tx_cb = PIOS_USB_HID_RegisterTxCallback,
     .bind_rx_cb = PIOS_USB_HID_RegisterRxCallback,
-    .available  = PIOS_USB_CheckAvailable,
+    .available  = PIOS_USB_HID_Available,
 };
 
 enum pios_usb_hid_dev_magic {
@@ -370,4 +371,9 @@ static void PIOS_USB_HID_EP_OUT_Callback(void)
 #endif /* PIOS_INCLUDE_FREERTOS */
 }
 
+static uint32_t PIOS_USB_HID_Available(uint32_t usbhid_id)
+{
+    return PIOS_USB_CheckAvailable(usbhid_id) ? COM_AVAILABLE_RXTX : COM_AVAILABLE_NONE;
+}
+
 #endif /* PIOS_INCLUDE_USB_HID */
diff --git a/flight/pios/stm32f4xx/pios_usb_cdc.c b/flight/pios/stm32f4xx/pios_usb_cdc.c
index 277165af2..830b26bad 100644
--- a/flight/pios/stm32f4xx/pios_usb_cdc.c
+++ b/flight/pios/stm32f4xx/pios_usb_cdc.c
@@ -43,7 +43,7 @@ static void PIOS_USB_CDC_RegisterRxCallback(uint32_t usbcdc_id, pios_com_callbac
 static void PIOS_USB_CDC_RegisterCtrlLineCallback(uint32_t usbcdc_id, pios_com_callback_ctrl_line ctrl_line_cb, uint32_t context);
 static void PIOS_USB_CDC_TxStart(uint32_t usbcdc_id, uint16_t tx_bytes_avail);
 static void PIOS_USB_CDC_RxStart(uint32_t usbcdc_id, uint16_t rx_bytes_avail);
-static bool PIOS_USB_CDC_Available(uint32_t usbcdc_id);
+static uint32_t PIOS_USB_CDC_Available(uint32_t usbcdc_id);
 
 const struct pios_com_driver pios_usb_cdc_com_driver = {
     .tx_start   = PIOS_USB_CDC_TxStart,
@@ -445,7 +445,7 @@ static bool PIOS_USB_CDC_CTRL_IF_Setup(uint32_t usb_cdc_id, struct usb_setup_req
     return true;
 }
 
-static bool PIOS_USB_CDC_Available(uint32_t usbcdc_id)
+static uint32_t PIOS_USB_CDC_Available(uint32_t usbcdc_id)
 {
     struct pios_usb_cdc_dev *usb_cdc_dev = (struct pios_usb_cdc_dev *)usbcdc_id;
 
@@ -453,8 +453,8 @@ static bool PIOS_USB_CDC_Available(uint32_t usbcdc_id)
 
     PIOS_Assert(valid);
 
-    return PIOS_USB_CheckAvailable(usb_cdc_dev->lower_id) &&
-           (control_line_state & USB_CDC_CONTROL_LINE_STATE_DTE_PRESENT);
+    return (PIOS_USB_CheckAvailable(usb_cdc_dev->lower_id) &&
+            (control_line_state & USB_CDC_CONTROL_LINE_STATE_DTE_PRESENT)) ? COM_AVAILABLE_NONE : COM_AVAILABLE_RXTX;
 }
 
 /**
diff --git a/flight/pios/stm32f4xx/pios_usb_hid.c b/flight/pios/stm32f4xx/pios_usb_hid.c
index f80c3a567..0d1e7928c 100644
--- a/flight/pios/stm32f4xx/pios_usb_hid.c
+++ b/flight/pios/stm32f4xx/pios_usb_hid.c
@@ -41,13 +41,14 @@ static void PIOS_USB_HID_RegisterTxCallback(uint32_t usbhid_id, pios_com_callbac
 static void PIOS_USB_HID_RegisterRxCallback(uint32_t usbhid_id, pios_com_callback rx_in_cb, uint32_t context);
 static void PIOS_USB_HID_TxStart(uint32_t usbhid_id, uint16_t tx_bytes_avail);
 static void PIOS_USB_HID_RxStart(uint32_t usbhid_id, uint16_t rx_bytes_avail);
+static uint32_t PIOS_USB_HID_Available(uint32_t usbhid_id);
 
 const struct pios_com_driver pios_usb_hid_com_driver = {
     .tx_start   = PIOS_USB_HID_TxStart,
     .rx_start   = PIOS_USB_HID_RxStart,
     .bind_tx_cb = PIOS_USB_HID_RegisterTxCallback,
     .bind_rx_cb = PIOS_USB_HID_RegisterRxCallback,
-    .available  = PIOS_USB_CheckAvailable,
+    .available  = PIOS_USB_HID_Available,
 };
 
 enum pios_usb_hid_dev_magic {
@@ -549,4 +550,9 @@ static bool PIOS_USB_HID_EP_OUT_Callback(uint32_t usb_hid_id, __attribute__((unu
     return rc;
 }
 
+static uint32_t PIOS_USB_HID_Available(uint32_t usbhid_id)
+{
+    return PIOS_USB_CheckAvailable(usbhid_id) ? COM_AVAILABLE_RXTX : COM_AVAILABLE_NONE;
+}
+
 #endif /* PIOS_INCLUDE_USB_HID */