Experimental: USBSerial: allow multiple callbacks on RX

Author: facchinm

cores/arduino/USB/PluggableUSBSerial.h

@@ -44,6 +44,8 @@
 * @endcode
 */
 
+#define MAX_CALLBACKS_ON_IRQ    4
+
 namespace arduino {
 
 
@@ -155,7 +157,7 @@ class USBSerial: public USBCDC, public ::mbed::Stream, public HardwareSerial {
         USBCDC::lock();
 
         if ((mptr != NULL) && (tptr != NULL)) {
-            rx = ::mbed::Callback<void()>(mptr, tptr);
+            rx[howManyCallbacks++] = ::mbed::Callback<void()>(mptr, tptr);
         }
 
         USBCDC::unlock();
@@ -171,7 +173,7 @@ class USBSerial: public USBCDC, public ::mbed::Stream, public HardwareSerial {
         USBCDC::lock();
 
         if (fptr != NULL) {
-            rx = ::mbed::Callback<void()>(fptr);
+            rx[howManyCallbacks++] = ::mbed::Callback<void()>(fptr);
         }
 
         USBCDC::unlock();
@@ -186,7 +188,7 @@ class USBSerial: public USBCDC, public ::mbed::Stream, public HardwareSerial {
     {
         USBCDC::lock();
 
-        rx = cb;
+        rx[howManyCallbacks++] = cb;
 
         USBCDC::unlock();
     }
@@ -270,7 +272,8 @@ class USBSerial: public USBCDC, public ::mbed::Stream, public HardwareSerial {
     }
 
 private:
-    ::mbed::Callback<void()> rx;
+    ::mbed::Callback<void()> rx[MAX_CALLBACKS_ON_IRQ];
+    int howManyCallbacks = 0;
     void (*_settings_changed_callback)(int baud, int bits, int parity, int stop);
 };
 }

cores/arduino/USB/USBSerial.cpp

@@ -94,8 +94,14 @@ void USBSerial::data_rx()
     USBCDC::assert_locked();
 
     //call a potential handler
-    if (rx) {
-        rx.call();
+    int i = 0;
+    while (i < howManyCallbacks) {
+        if (rx[i]) {
+            rx[i].call();
+        } else {
+            break;
+        }
+        i++;
     }
 }