diff --git a/firmware/hackrf_usb/hackrf_usb.c b/firmware/hackrf_usb/hackrf_usb.c
index e4cd3da3..86a1ab13 100644
--- a/firmware/hackrf_usb/hackrf_usb.c
+++ b/firmware/hackrf_usb/hackrf_usb.c
@@ -884,48 +884,16 @@ const usb_request_handlers_t usb_request_handlers = {
 	.reserved = 0,
 };
 
-// TODO: Seems like this should live in usb_standard_request.c.
-bool usb_set_configuration(
-	usb_device_t* const device,
-	const uint_fast8_t configuration_number
+void usb_configuration_changed(
+	usb_device_t* const device
 ) {
-	const usb_configuration_t* new_configuration = 0;
-	if( configuration_number != 0 ) {
-		
-		// Locate requested configuration.
-		if( device->configurations ) {
-			usb_configuration_t** configurations = *(device->configurations);
-			uint32_t i = 0;
-			const usb_speed_t usb_speed_current = usb_speed(device);
-			while( configurations[i] ) {
-				if( (configurations[i]->speed == usb_speed_current) &&
-				    (configurations[i]->number == configuration_number) ) {
-					new_configuration = configurations[i];
-					break;
-				}
-				i++;
-			}
-		}
-
-		// Requested configuration not found: request error.
-		if( new_configuration == 0 ) {
-			return false;
-		}
-	}
+	set_transceiver_mode(transceiver_mode);
 	
-	if( new_configuration != device->configuration ) {
-		// Configuration changed.
-		device->configuration = new_configuration;
-		set_transceiver_mode(transceiver_mode);
-
-		if( device->configuration ) {
-			gpio_set(PORT_LED1_3, PIN_LED1);
-		} else {
-			gpio_clear(PORT_LED1_3, PIN_LED1);
-		}
+	if( device->configuration->number ) {
+		gpio_set(PORT_LED1_3, PIN_LED1);
+	} else {
+		gpio_clear(PORT_LED1_3, PIN_LED1);
 	}
-
-	return true;
 };
 
 void sgpio_irqhandler() {
diff --git a/firmware/hackrf_usb/usb.h b/firmware/hackrf_usb/usb.h
index ccaa9184..4b1d50f4 100644
--- a/firmware/hackrf_usb/usb.h
+++ b/firmware/hackrf_usb/usb.h
@@ -28,13 +28,6 @@
 
 #include "usb_type.h"
 
-// TODO: This is a lame move, requiring an extern to be defined to complete
-// the interface between this API and the application.
-extern bool usb_set_configuration(
-	usb_device_t* const device,
-	const uint_fast8_t configuration_number
-);
-
 void usb_peripheral_reset();
 
 void usb_device_init(
diff --git a/firmware/hackrf_usb/usb_standard_request.c b/firmware/hackrf_usb/usb_standard_request.c
index 71a38232..cfb58ee0 100644
--- a/firmware/hackrf_usb/usb_standard_request.c
+++ b/firmware/hackrf_usb/usb_standard_request.c
@@ -20,6 +20,7 @@
  */
 
 #include <stdint.h>
+#include <stddef.h>
 
 #include "usb_standard_request.h"
 
@@ -58,10 +59,51 @@ usb_transfer_type_t usb_endpoint_descriptor_transfer_type(
 	return (endpoint_descriptor[3] & 0x3);
 }
 
-extern bool usb_set_configuration(
+void (*usb_configuration_changed_cb)(usb_device_t* const) = NULL;
+
+void usb_set_configuration_changed_cb(
+	void (*callback)(usb_device_t* const)
+) {
+	usb_configuration_changed_cb = callback;
+}
+
+bool usb_set_configuration(
 	usb_device_t* const device,
 	const uint_fast8_t configuration_number
-);
+) {
+
+	const usb_configuration_t* new_configuration = 0;
+	if( configuration_number != 0 ) {
+		
+		// Locate requested configuration.
+		if( device->configurations ) {
+			usb_configuration_t** configurations = *(device->configurations);
+			uint32_t i = 0;
+			const usb_speed_t usb_speed_current = usb_speed(device);
+			while( configurations[i] ) {
+				if( (configurations[i]->speed == usb_speed_current) &&
+				    (configurations[i]->number == configuration_number) ) {
+					new_configuration = configurations[i];
+					break;
+				}
+				i++;
+			}
+		}
+
+		// Requested configuration not found: request error.
+		if( new_configuration == 0 ) {
+			return false;
+		}
+	}
+	
+	if( new_configuration != device->configuration ) {
+		// Configuration changed.
+		device->configuration = new_configuration;
+		if (usb_configuration_changed_cb)
+			usb_configuration_changed_cb(device);
+	}
+	return true;
+}
 	
 static usb_request_status_t usb_send_descriptor(
 	usb_endpoint_t* const endpoint,
diff --git a/firmware/hackrf_usb/usb_standard_request.h b/firmware/hackrf_usb/usb_standard_request.h
index 5a0bdac6..77fd1b10 100644
--- a/firmware/hackrf_usb/usb_standard_request.h
+++ b/firmware/hackrf_usb/usb_standard_request.h
@@ -25,6 +25,10 @@
 #include "usb_type.h"
 #include "usb_request.h"
 
+void usb_set_configuration_changed_cb(
+        void (*callback)(usb_device_t* const)
+);
+
 usb_request_status_t usb_standard_request(
 	usb_endpoint_t* const endpoint,
 	const usb_transfer_stage_t stage
@@ -42,4 +46,9 @@ usb_transfer_type_t usb_endpoint_descriptor_transfer_type(
 	const uint8_t* const endpoint_descriptor
 );
 
+bool usb_set_configuration(
+	usb_device_t* const device,
+	const uint_fast8_t configuration_number
+);
+
 #endif//__USB_STANDARD_REQUEST_H__