[2.0.x] LPC176x Serial cleanup (#11032)

frameworks/CMSIS/LPC1768/lib/Print.h

@@ -40,7 +40,8 @@ class Print {
     void setWriteError(const int err = 1) { write_error = err; }
   public:
     Print() : write_error(0) {}
-
+    virtual ~Print() {}
+    
     int getWriteError() { return write_error; }
     void clearWriteError() { setWriteError(0); }
 
@@ -74,7 +75,7 @@ class Print {
     size_t println(double, int = 2);
     size_t println(const Printable&);
     size_t println(void);
-    size_t printf(const char *argList, ...);
+    virtual size_t printf(const char *argList, ...);
 };
 
 #endif // _CMSIS_PRINT_H_

frameworks/CMSIS/LPC1768/lib/Stream.h

@@ -47,9 +47,9 @@ class Stream : public Print
     int peekNextDigit(); // returns the next numeric digit in the stream or -1 if timeout
 
   public:
-    virtual int available() = 0;
-    virtual int read() = 0;
-    virtual int peek() = 0;
+    virtual size_t available() = 0;
+    virtual int16_t read() = 0; // signed int required for error (empty buffer) value
+    virtual int16_t peek() = 0;
     virtual void flush() = 0;
 
     Stream() {_timeout=1000;}

frameworks/CMSIS/LPC1768/lib/usb/cdcuser.cpp

@@ -211,7 +211,7 @@ void CDC_BulkIn(void) {
   if (numBytesAvail > 0) {
     numBytesAvail = numBytesAvail > (USB_CDC_BUFSIZE - 1) ? (USB_CDC_BUFSIZE - 1) : numBytesAvail;
     for(uint32_t i = 0; i < numBytesAvail; ++i) {
-      BulkBufIn[i] = usb_serial.transmit_buffer.read(); //todo: optimise
+      usb_serial.transmit_buffer.read(&BulkBufIn[i]);
     }
     USB_WriteEP(CDC_DEP_IN, &BulkBufIn[0], numBytesAvail);
   } else {