diff --git a/stm32/aioc-fw/Src/usb_serial.c b/stm32/aioc-fw/Src/usb_serial.c
index cfd0f7d..995e8f8 100644
--- a/stm32/aioc-fw/Src/usb_serial.c
+++ b/stm32/aioc-fw/Src/usb_serial.c
@@ -251,3 +251,32 @@ void USB_SerialTask(void)
 {
 
 }
+
+#include "device/usbd_pvt.h"
+
+bool USB_SerialSendLineState(uint8_t lineState)
+{
+#if 0
+    /* TODO: This causes issues with the stack if its being called before CDC was initialized? Crashes on terminal connect */
+    uint8_t const rhport = 0;
+    static uint8_t notification[10] = {
+        /* bmRequestType */ 0xA1,
+        /* bNotification */ 0x20,
+        /* wValue */ 0x00, 0x00,
+        /* wIndex */ ITF_NUM_CDC_0, 0x00,
+        /* wLength */ 0x02, 0x00,
+        /* Data */ 0x00, 0x00
+    };
+
+    notification[8] = lineState;
+    notification[9] = 0x00;
+
+    // claim endpoint
+    TU_VERIFY( usbd_edpt_claim(rhport, EPNUM_CDC_0_NOTIF) );
+
+    return usbd_edpt_xfer(rhport, EPNUM_CDC_0_NOTIF, notification, sizeof(notification));
+#else
+    return true;
+#endif
+}
+
diff --git a/stm32/aioc-fw/Src/usb_serial.h b/stm32/aioc-fw/Src/usb_serial.h
index 51aaaa4..27d2237 100644
--- a/stm32/aioc-fw/Src/usb_serial.h
+++ b/stm32/aioc-fw/Src/usb_serial.h
@@ -1,6 +1,9 @@
 #ifndef USB_SERIAL_H_
 #define USB_SERIAL_H_
 
+#include <stdint.h>
+#include <stdbool.h>
+
 #define USB_SERIAL_UART             USART1
 #define USB_SERIAL_UART_IRQ         USART1_IRQHandler
 #define USB_SERIAL_UART_PERIPHCLK   RCC_PERIPHCLK_USART1
@@ -10,7 +13,14 @@
 #define USB_SERIAL_UART_PIN_TX      GPIO_PIN_9
 #define USB_SERIAL_UART_PIN_RX      GPIO_PIN_10
 
+#define USB_SERIAL_LINESTATE_DCD    0x01
+#define USB_SERIAL_LINESTATE_DSR    0x02
+#define USB_SERIAL_LINESTATE_BREAK  0x04
+#define USB_SERIAL_LINESTATE_RI     0x08
+
 void USB_SerialInit(void);
 void USB_SerialTask(void);
 
+bool USB_SerialSendLineState(uint8_t lineState);
+
 #endif /* USB_SERIAL_H_ */