Initial commit of files

src/libPIC/pkt_recv.c

@@ -0,0 +1,297 @@
+/*****************************************************************************
+ * Copyright (C) 2008
+ * ProbeStar Telematics, LLC
+ * All Rights Reserved.  Proprietary and Confidential.
+ *============================================================================
+ * Packet Receive
+ *----------------------------------------------------------------------------
+ * Details
+*****************************************************************************/
+
+/*****************************************************************************
+ * includes
+*****************************************************************************/
+
+#include "system.h"
+#include "delay.h"
+#include "types.h"
+#include "serial.h"
+#include "packet.h"
+
+/*****************************************************************************
+ * defines
+*****************************************************************************/
+
+/*****************************************************************************
+ * macros
+*****************************************************************************/
+
+/*****************************************************************************
+ * structs & typedefs
+*****************************************************************************/
+
+/*****************************************************************************
+ * global constants
+*****************************************************************************/
+
+/*****************************************************************************
+ * global variables
+*****************************************************************************/
+
+/*****************************************************************************
+ * static constants
+*****************************************************************************/
+
+/*****************************************************************************
+ * static variables
+*****************************************************************************/
+
+/*****************************************************************************
+ * static prototypes
+*****************************************************************************/
+
+/*****************************************************************************
+ * C functions
+*****************************************************************************/
+
+///////////////////////////////////////////////////////////////////////////////
+// de-Packetizer
+///////////////////////////////////////////////////////////////////////////////
+
+void recvClear( BYTE n )
+{
+	// clear buffer till end of current packet
+	n++;
+	while ( n-- && getchavail() )
+		getch();
+}
+
+void recvFlush( void )
+{
+	// flush queue
+	SerialClear();
+}
+
+int recvGet( BYTE n )
+{
+	int c;
+	BYTE i;
+	UINT t;
+	DWORD v = 0;
+
+	for ( i = 0; i < n; i++ )
+	{
+		t = TIMEOUT;
+		if ( ( c = getchtimeout( &t ) ) < 0 )
+			return PACKET_ERR_TIMEOUT;
+		v |= ( c << ( i * 8 ) );
+	}
+	return v;
+}
+
+int recvWait( UINT iWait )
+{
+	iWait /= 10;
+
+	// wait for a packet
+	while ( iWait-- )
+	{
+		if ( getchavail() > 0 )
+			return 1;
+		DelayUsec( 100 );
+	}
+	return 0;
+}
+
+int recvHeader( WORD *pwCheck, WORD *pwId, BYTE *pbyFlag )
+{
+	int c = 0;
+	WORD n = 0;
+	UINT t;
+
+	// software timeouts
+	// check if line needs to turn around
+	if ( dirRadio( RADIO_LISTEN ) )
+	{
+		// generous wait for a packet
+		if ( !recvWait( PACKET_WAIT_TIME ) )
+			return PACKET_ERR_TIMEOUT;
+	}
+	else
+	{
+		// wait for next packet
+		if ( !recvWait( PACKET_WAIT_TIME/2 ) )
+			return PACKET_ERR_TIMEOUT;
+	}
+
+	// wait till synchronization string
+	while ( n < PACKET_SYNC_LENGTH )
+	{
+		t = TIMEOUT;
+		c = getchtimeout( &t );
+
+		if ( c == PACKET_RECV_SYNC )
+		{
+			if ( n < PACKET_SYNC_LENGTH - 1 )
+				n++;
+		}
+		else if ( c == PACKET_SYNC_CHAR )
+		{
+			if ( n == PACKET_SYNC_LENGTH - 1 )
+				n++;
+			else
+				n = 0;
+		}
+		else if ( c < 0 )
+			return c;
+		else
+			n = 0;
+	}
+
+#ifdef PACKET_FILTER
+	// got it
+	if ( g_byPacketAvail )
+		g_byPacketAvail--;
+#endif
+	// init checksum or CRC
+	*pwCheck = 0;
+
+	// id
+	*pwId = (WORD) recvGet( PACKET_ID_SIZE );
+
+	// flag byte
+	*pbyFlag = (BYTE) recvGet( PACKET_FL_SIZE );
+
+	// byte count
+	n = (WORD) recvGet( PACKET_BC_SIZE );
+
+	// check flag
+	if ( *pbyFlag )
+	{
+		// check control flag bits
+		if ( *pbyFlag & PACKET_FLAG_STREAM )
+			return n;	// ignore rest of bits used for streaming counter
+
+		// check each flag
+		if ( *pbyFlag & PACKET_FLAG_CRC )
+			g_bPacketCRC = 1;
+	}
+
+	return n;
+}
+
+int recvByte( WORD *pwCheck )
+{
+	UINT t = TIMEOUT;
+	int c;
+
+	if ( ( c = getchtimeout( &t ) ) < 0 )
+		return c;
+
+	if ( g_bPacketCRC )
+		*pwCheck = doCRC16( *pwCheck, c );
+	else
+		*pwCheck += (BYTE) c;
+	return (BYTE) c;
+}
+
+int recvData( WORD *pwCheck, PKTBANK BYTE * pbyData, WORD nBytes, WORD maxBytes )
+{
+	WORD nRead = 0;
+	UINT t;
+	int c;
+
+	// read bytes
+	while ( nBytes-- )
+	{
+		// read
+		t = TIMEOUT;
+		c = getchtimeout( &t );
+		if ( c < 0 )
+			return c;
+
+		// store data away
+		if ( pbyData && ( nRead < maxBytes ) )
+			*pbyData++ = c;
+
+		// CRC or checksum
+		if ( g_bPacketCRC )
+			*pwCheck = doCRC16( *pwCheck, c );
+		else
+			*pwCheck += (BYTE) c;
+
+		// count
+		nRead++;
+	}
+
+	return nRead;
+}
+
+int recvTrailer( WORD *pwCheck )
+{
+	UINT t = TIMEOUT;
+	WORD wCheck;
+	int c;
+
+	if ( ( c = getchtimeout( &t ) ) < 0 )
+		return c;
+
+	// CRC or checksum
+	if ( g_bPacketCRC )
+	{
+		// low byte
+		wCheck = c;
+		// high byte
+		if ( ( c = getchtimeout( &t ) ) < 0 )
+			return c;
+		wCheck |= (c << 8);
+
+		// compare CRCs
+		if ( *pwCheck != wCheck )
+			return 0;
+	}
+	else
+	{
+		// byte, masked
+		*pwCheck += (BYTE) c;
+		*pwCheck &= 0xff;
+
+		// good checksum is zero
+		if ( *pwCheck )
+			return 0;
+	}
+	return 1;
+}
+
+int recvPacket( WORD *pwId, PKTBANK BYTE *pbyPacket, BYTE *pbyFlag, WORD maxBytes )
+{
+	WORD wCheck;
+	int nBytes;
+
+	// header
+	if ( ( nBytes = recvHeader( &wCheck, pwId, pbyFlag ) ) < 0 )
+		return nBytes;
+
+	// check
+	if ( nBytes > maxBytes )
+		return PACKET_BUF_TOOBIG;
+
+	// data
+	if ( ( nBytes = recvData( &wCheck, pbyPacket, (WORD)nBytes, (WORD)maxBytes ) ) < 0 )
+		return nBytes;
+
+	// checksum
+	if ( recvTrailer( &wCheck ) )
+		return nBytes;
+	return PACKET_BAD_CHECKSUM;
+}
+
+int recvFinish( WORD nBytes )
+{
+	WORD wCheck;
+
+	recvData( &wCheck, NULL, nBytes, nBytes );
+	if ( recvTrailer( &wCheck ) )
+		return nBytes;
+	return PACKET_BAD_CHECKSUM;
+}