Diff: com.cpp

Revision:

0:26a151d2c6db

Child:

1:4f53de75bc96

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/com.cpp	Wed Jan 08 07:32:30 2014 +0000
@@ -0,0 +1,146 @@
+/****************************** com.cpp **********************************/
+/* Version: 1.0                                                          */
+/* Last Updated: June 1, 2013                                            */
+/*                                                                       */
+/* The com class implements reliable data transfer between two nodes     */
+/*using a checksum and a sequence number for guaranteed message delivery */
+/*over an xbee modem connected to the passed in tx and rx pins. Messages */
+/*are received and placed in the rxBuffer to be read when convenient.    */
+/*Messages are encoded by sending a byte with the value of the command   */
+/*then and int of the command.                                           */
+/*                                                                       */
+/* Commands:    0 -> Ack, does not get placed in rxQueue.                */
+/*              1 -> Throttle                                            */
+/*              2 -> Pitch                                               */
+/*              3 -> Roll                                                */
+/*              4 -> Yaw                                                 */
+/*************************************************************************/
+
+#include "mbed.h"
+#include "com.h"
+
+/*********************** com( PinName, PinName ) *************************/
+/*                                                                       */
+/*************************************************************************/
+
+com::com( PinName tx, PinName rx , PinName rssipin) : xbeeRx( tx, rx), xbeeTx( tx, rx), rssi(rssipin)
+{
+    bLength = 0;                            // How many bytes are in the buffer.
+    xbeeRx.baud(BAUDRATE);                    // Setup the serial baud rate.
+    xbeeTx.baud(BAUDRATE);                    // Setup the serial baud rate.
+    rxBuffer = new queue();                 // Point to the rxQueue.
+    signalStrength = 0;
+    xbeeRx.attach( this, &com::callback );    // Set callback as the interrupt handler. 
+    xbeeTx.printf("Communication.....Done\n\r");
+}
+
+/************************* bool isData()  ********************************/
+/*                                                                       */
+/*************************************************************************/
+
+bool com::isData()
+{
+    if( rxBuffer->isEmpty() )
+        return false;
+        
+    return true;
+}
+
+/************************ void write( char ) *****************************/
+/* Write a packet out the xbee com port.                                 */
+/*                                                                       */
+/* Data format byte[]                                                    */
+/*                byte[0] = command.                                     */
+/*                byte[1] = upper 8 bits of value.                       */
+/*                byte[2] = lower 8 bits of value.                       */
+/*                byte[3] = Checksum byte[0] + byte[2].                  */
+/*                byte[4] = Sequence Number.                             */
+/*                byte[5] = 255 End of message.                          */
+/*************************************************************************/
+
+void com::write( short command, short value  )
+{
+    xbeeTx.putc( (char)command );     // Command
+    xbeeTx.putc( 0 );                 // First 8 bits in array. 
+    xbeeTx.putc( (char)value );       // Second 8 bits in array.
+    xbeeTx.putc( command + value );   // Checksum array[0] + array[1].
+    xbeeTx.putc( 0 );                 // Sequence number.
+    xbeeTx.putc( 255 );               // End of message.
+}
+
+/*************************** char read()  ********************************/
+/*                                                                       */
+/*************************************************************************/
+
+short * com::read()
+{
+    if( !rxBuffer->isEmpty())
+        return rxBuffer->pop();
+        
+    return NULL;
+}
+
+/************************ void callback() ********************************/
+/*                                                                       */
+/*************************************************************************/
+
+void com::callback()
+{   
+    while( xbeeRx.readable() )
+    {
+        char data = xbeeRx.getc(); 
+//        xbeeTx.printf("data: %d\n\r", data);
+        if( bLength++ < BUFFERSIZE )
+            buffer[bLength] = data;      
+     
+        if( data == 255 )
+            packetBuilder();
+    }
+}
+
+/********************** void packetBuilder() *****************************/
+/* Creates a packet from the buffered data and places it in the rxBuffer */
+/* queue to be read whenever convenient. Max value of +/- 8063.          */
+/*************************************************************************/
+
+void com::packetBuilder()
+{
+    char * commandData = new char[bLength];
+    commandData[4] = buffer[--bLength];     // Sequence Number.
+    commandData[3] = buffer[--bLength];     // CheckSum value.
+    commandData[2] = buffer[--bLength];     // Second 7 bits.
+    commandData[1] = buffer[--bLength];     // Fisrt 7 bits.
+    commandData[0] = buffer[--bLength];     // Command.
+    
+      
+    if( commandData[0] + commandData[2] == commandData[3] ) // Validate checksum.
+    {
+        short * array = new short[2];
+        
+        array[0] = (short)commandData[0];
+        
+        short value = (short)(commandData[1] * 128 + commandData[2]);
+        
+        if( value > 8062 )
+            value = (short)value + 57344;
+        
+        array[1] = value;
+//        xbeeTx.printf("Cmd: %d,\tVal: %d\n\r,",array[0],array[1]);
+        rxBuffer->add( array );   // Add to read buffer.
+        write( (short)commandData[0], (short)commandData[4]); // Ack the packet with sequence nuber.
+    } 
+    delete[] commandData;
+    bLength = 0;    // Reset the buffer length.                                           
+}
+
+
+/********************** bool isSignalGood() ******************************/
+/* For future use   */
+/*************************************************************************/
+bool com::isSignalGood()
+{
+    signalStrength = rssi.dutycycle();
+    if (signalStrength > RSSI_THRES) return true;
+    else return false;
+}
+