[tinyusb] Only read from CDC if data is available

Author: salkinium

examples/generic/usb/main.cpp

@@ -46,6 +46,12 @@ int main()
 		tud_task();
 		midi_task();
 
+#if CFG_TUD_CDC
+		// Do a loopback on the CDC
+		if (char input; usb_stream0.get(input), input != modm::IOStream::eof) {
+			usb_stream0 << input;
+		}
+#endif
 		if (tmr.execute())
 		{
 			Leds::toggle();

ext/hathach/uart.hpp

@@ -29,6 +29,12 @@ class UsbUart : public modm::Uart
 		return tud_cdc_n_connected(ITF);
 	}
 
+	static inline void
+	flushWriteBuffer()
+	{
+		tud_cdc_n_write_flush(ITF);
+	}
+
 	static inline bool
 	write(uint8_t c)
 	{
@@ -45,22 +51,26 @@ class UsbUart : public modm::Uart
 		return rc;
 	}
 
-	static inline void
-	flushWriteBuffer()
+	static inline bool
+	isWriteFinished()
 	{
-		tud_cdc_n_write_flush(ITF);
+		return not transmitBufferSize();
 	}
 
 	static inline bool
 	read(uint8_t& c)
 	{
-		return tud_cdc_n_read(ITF, &c, sizeof(uint8_t));
+		if (receiveBufferSize())
+			return tud_cdc_n_read(ITF, &c, sizeof(uint8_t));
+		return false;
 	}
 
 	static inline std::size_t
 	read(uint8_t *data, std::size_t length)
 	{
-		return tud_cdc_n_read(ITF, data, length);
+		if (receiveBufferSize())
+			return tud_cdc_n_read(ITF, data, length);
+		return 0;
 	}
 
 	static inline std::size_t
@@ -69,11 +79,37 @@ class UsbUart : public modm::Uart
 		return tud_cdc_n_available(ITF);
 	}
 
+	static inline std::size_t
+	discardReceiveBuffer()
+	{
+		const std::size_t rxsize = receiveBufferSize();
+		tud_cdc_n_read_flush(ITF);
+		return rxsize;
+	}
+
 	static inline std::size_t
 	transmitBufferSize()
 	{
 		return tud_cdc_n_write_available(ITF);
 	}
+
+	static inline std::size_t
+	discardTransmitBuffer()
+	{
+		const std::size_t txsize = transmitBufferSize();
+		tud_cdc_n_write_clear(ITF);
+		return txsize;
+	}
+
+	static inline bool
+	hasError()
+	{
+		return false;
+	}
+
+	static inline void
+	clearError()
+	{}
 };
 
 using UsbUart0 = UsbUart<0>;