Diff: example3b.cpp

Revision:

18:21ef26402365

diff -r 6c9b57c14868 -r 21ef26402365 example3b.cpp
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+++ b/example3b.cpp	Thu Apr 21 09:20:41 2011 +0000
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+/*
+    Copyright (c) 2011 Andy Kirkham
+ 
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+ 
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+ 
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+    
+    @file          example3b.cpp 
+    @purpose       Demos a simple filter.
+    @version       see ChangeLog.c
+    @author        Andy Kirkham
+*/
+
+/*
+    This example shows how to use the new callback system. In the old system
+    Mbed's FunctionPointer[1] type was used to store abd make calls to callbacks.
+    However, that limits the callback function prototype to void func(void);
+    which means we cannot pass parameters.
+    
+    This latest version of MODSERIAL now uses its own callback object. This allows
+    the passing of a pointer to a class that holds information about the MODSERIAL
+    object making the callback. As of version 1.18 one critcal piece of information
+    is passed, a pointer to the MODSERIAL object. This allows callbacks to use the
+    MODSERIAL functions and data.
+        
+    Additionally, since MODSERIAL and the callback parameter class MODSERIAL_IRQ_INFO
+    are friends, MODSERIAL_IRQ_INFO can access the protected functions of MODSERIAL.
+    This is used to ensure functions that can only be called during a callback
+    can be invoked from a callback. 
+    
+    [1] http://mbed.org/projects/libraries/svn/mbed/trunk/FunctionPointer.h    
+*/
+
+
+#ifdef COMPILE_EXAMPLE3_CODE_MODSERIAL
+
+#include "mbed.h"
+#include "MODSERIAL.h"
+
+void rxCallback(MODSERIAL_IRQ_INFO *info) {
+
+    // Get the pointer to our MODSERIAL object that invoked this callback.
+    MODSERIAL *pc = info->serial;
+    
+    // info->serial points at the MODSERIAL instance so we can use it to call
+    // any of the public MODSERIAL functions that are normally available. So
+    // there's now no need to use the global version (pc in our case) inside
+    // callback functions.    
+    char c = pc->rxGetLastChar(); // Where local pc variable is a pointer to the global MODSERIAL pc object.
+    
+    // The following is rather daft but demos the point.
+    // Don't allow the letter "A" go into the RX buffer.
+    // Basically acts as a filter to remove the letter "A" 
+    // if it goes into the RX buffer.
+    if (c == 'A') {
+        // Note, we call the MODSERIAL_IRQ_INFO::rxDiscardLastChar() public function which
+        // is permitted access to the protected version of MODSERIAL::rxDiscardLastChar()
+        // within MODSERIAL (because they are friends). This ensures rxDiscardLastChar()
+        // can only be called within an rxCallback function. 
+        info->rxDiscardLastChar(); 
+    }
+}
+
+#endif