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99 lines
3.9 KiB
C
Executable File
99 lines
3.9 KiB
C
Executable File
/*! \file stxetx.h \brief STX/ETX Packet Protocol Implementation Library. */
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//*****************************************************************************
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//
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// File Name : 'stxetx.h'
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// Title : STX/ETX Packet Protocol Implementation Library
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// Author : Pascal Stang - Copyright (C) 2002-2003
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// Created : 10/9/2002
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// Revised : 02/10/2003
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// Version : 0.1
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// Target MCU : any
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// Editor Tabs : 4
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//
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// Description : This library provides a set of functions needed to send and
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// receive STX/ETX packets. STX/ETX is a simple packet protocol that can
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// be wrapped around user data for one or more of the following reasons:
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//
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// 1. packetization is needed
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// - Using packets can be helpful if your data naturally forms
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// little "bunches" or if different types of data must be sent
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// over the same channel (a serial cable, for example). If your
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// data forms "bunches", you can send user data inside STX/ETX
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// packets with a predetermined structure, like an array of A/D
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// conversion results. If you need a way to tell the receiver
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// what kind of data you're sending, you can use the TYPE field
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// in the STX/ETX packet.
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// 2. error checking is needed
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// - STX/ETX packets will add a checksum to your data. This
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// allows the receiver to verify that data was received correctly
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// and is error-free. Packets which are corrupted in transmission
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// and fail the the checksum test are automatically discarded.
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// Error checking is especially useful when the data transmission
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// channel is unreliable or noisy (examples: radio, infrared, long
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// cables, etc)
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//
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// STX/ETX packets have the following structure:
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//
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// [STX][status][type][length][user data...][checksum][ETX]
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//
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// All fields are 1 byte except for user data which may be 0-255 bytes.
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// Uppercase fields are constant (STX=0x02, ETX=0x03), lowercase fields
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// vary. The length field is the number of bytes in the user data area.
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// The checksum is the 8-bit sum of all bytes between but not including
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// STX/ETX.
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//
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// This code is distributed under the GNU Public License
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// which can be found at http://www.gnu.org/licenses/gpl.txt
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//
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//*****************************************************************************
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#ifndef STXETX_H
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#define STXETX_H
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#include "buffer.h"
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// include project-dependent configuration options
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#include "stxetxconf.h"
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// constants
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// packet markers
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#define STX 0x02 // start transmission marker
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#define ETX 0x03 // end transmission marker
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// packet length parameters
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#define STXETX_HEADERLENGTH 4 // number of bytes required for packet header
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#define STXETX_TRAILERLENGTH 2 // number of bytes required for packet trailer
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// packet field offsets
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#define STXETX_STATUSOFFSET 1 // number of bytes from STX to STATUS
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#define STXETX_TYPEOFFSET 2 // number of bytes from STX to TYPE
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#define STXETX_LENGTHOFFSET 3 // number of bytes from STX to LENGTH
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#define STXETX_DATAOFFSET 4 // number of bytes from STX to the data
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#define STXETX_CHECKSUMOFFSET 4 // number of bytes from STX+[length] to CHECKSUM
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#define STXETX_NOETXSTXCHECKSUM 3 // number of bytes used by STX,ETX,CHECKSUM
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// function prototypes
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//! Initialize STX/ETX packet protocol library
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void stxetxInit(void (*dataout_func)(unsigned char data));
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//! Send/Create STX/ETX packet
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void stxetxSend(unsigned char status, unsigned char type, unsigned char datalength, unsigned char* dataptr);
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//! Process a buffer containing STX/ETX packets
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unsigned char stxetxProcess(cBuffer* rxBuffer);
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//! Returns the received packet's status
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unsigned char stxetxGetRxPacketStatus(void);
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//! Returns the received packet's type
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unsigned char stxetxGetRxPacketType(void);
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//! Returns the received packet's datalength
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unsigned char stxetxGetRxPacketDatalength(void);
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//! Returns pointer to the received packet's data
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unsigned char* stxetxGetRxPacketData(void);
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#endif
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