Improve behaviour on full USB buffer

Software/VNA_embedded/Application/Drivers/USB/usb.c

@@ -284,3 +284,8 @@ void USB_LP_IRQHandler(void)
 uint16_t usb_available_buffer() {
 	return sizeof(usb_transmit_fifo) - usb_transmit_fifo_level;
 }
+
+void usb_clear_buffer() {
+	usb_transmit_fifo_level = 0;
+	data_transmission_active = 0;
+}

Software/VNA_embedded/Application/Drivers/USB/usb.h

@@ -21,7 +21,7 @@ void usb_init(usbd_recv_callback_t receive_callback);
 bool usb_transmit(const uint8_t *data, uint16_t length);
 uint16_t usb_available_buffer();
 void usb_log(const char *log, uint16_t length);
-
+void usb_clear_buffer();
 
 #ifdef __cplusplus
 }

Software/VNA_embedded/Application/Hardware.cpp

@@ -231,6 +231,7 @@ void HW::SetIdle() {
 	FPGA::Enable(FPGA::Periphery::Port2Mixer, false);
 	FPGA::Enable(FPGA::Periphery::RefMixer, false);
 	FPGA::Enable(FPGA::Periphery::PortSwitch, false);
+	activeMode = Mode::Idle;
 }
 
 HW::AmplitudeSettings HW::GetAmplitudeSettings(int16_t cdbm, uint64_t freq, bool applyCorrections, bool port2) {

Software/VNA_embedded/Application/VNA.cpp

@@ -408,7 +408,17 @@ void VNA::SweepHalted() {
 		// This function is called from a low level interrupt, need to dispatch to lower priority to allow USB
 		// handling to continue
 		STM::DispatchToInterrupt([](){
-			while(usb_available_buffer() < reservedUSBbuffer);
+			uint32_t start = HAL_GetTick();
+			while(usb_available_buffer() < reservedUSBbuffer) {
+				if(HAL_GetTick() - start > 100) {
+					// still no buffer space after some time, something more serious must have gone wrong
+					// -> abort sweep and return to idle
+					usb_clear_buffer();
+					FPGA::AbortSweep();
+					HW::SetIdle();
+					return;
+				}
+			}
 			FPGA::ResumeHaltedSweep();
 		});
 	}