RS485.h

00001 
00002 /**
00003  * @file    RS485.h
00004  * @brief   RS485 protocol - using half duplex method
00005  * @author  Aaron Allar
00006  * @version 1.0
00007  * @see
00008  *
00009  * based on this method https://www.gammon.com.au/forum/?id=11428
00010  * 
00011  * Can send from 1 to 255 bytes from one node to another with:
00012  *
00013  * Packet start indicator (STX)
00014  * Each data byte is doubled and inverted to check validity
00015  * Packet end indicator (ETX)
00016  * Packet CRC (checksum)
00017  */
00018 
00019 
00020 
00021 #ifndef RS485_H
00022 #define RS485_H
00023 
00024 #include "BufferedSerial.h"
00025 #include "mbed.h"
00026 
00027 /** RS485 Library
00028  *  
00029  * Can send from 1 to 255 bytes from one node to another with:
00030  *
00031  * Packet start indicator (STX)
00032  * Each data byte is doubled and inverted to check validity
00033  * Packet end indicator (ETX)
00034  * Packet CRC (checksum)
00035  *
00036  * Using MAX485 modules or the MAX485 CSA+
00037  *
00038  * Example:
00039  * @code
00040  *  #include "mbed.h" 
00041  *  #include <RS485.h>
00042  *  Serial pc(USBTX, USBRX); 
00043  *  RS485 RS485(PC_10,PC_11,PB_3); // Tx, Rx , !RE and DE MAX485 pin
00044  * 
00045  *  DigitalOut ho(PB_3); // this pin should be connected to !RE and DE
00046  *  typedef uint8_t byte;
00047  * 
00048  *  byte regvalue[9];
00049  *  byte data[9] = {0x01,0x04,0x00,0x48,0x00,0x02,0xf1,0xdd};//your data
00050  *  int main()
00051  *  {
00052  *    pc.printf("main\n");
00053  *    while(1) {
00054  *       pc.printf("Starting\n");
00055  *       ho = 1;                  // Enable sending on MAX485
00056  *       RS485.sendMsg(data,sizeof(data));
00057  *       wait_ms(600);            // Must wait for all the data to be sent   
00058  *       ho = 0;                  // Enable receiving on MAX485
00059  *       pc.printf("Getting data\n");
00060  *       if(RS485.readable() >0){
00061  *           memset(regvalue,0,sizeof(regvalue));
00062  *           wait_ms(200);
00063  *           RS485.recvMsg(regvalue,sizeof(data),500);
00064  *           wait_ms(200);
00065  *           for (int count = 0; count < 9; count++) {
00066  *               pc.printf("%X - ", regvalue[count]);
00067  *           }
00068  *       }else printf("No Data\n");
00069  *       printf("Done\n");
00070  *       wait_ms(1000);
00071  *    }
00072  *  } 
00073  * @endcode
00074  */
00075 
00076 
00077 /**
00078  *  @class RS485
00079  *  @communicating 
00080  */
00081 
00082 class RS485 : public BufferedSerial
00083 {
00084 private:
00085     typedef unsigned int word;
00086     typedef uint8_t byte;
00087     typedef uint8_t boolean;
00088     typedef void (*voidFuncPtr)(void);
00089     
00090 public:
00091     /** Create a BufferedSerial port, connected to the specified transmit and receive pins
00092      *  @param tx Transmit pin
00093      *  @param rx Receive pin
00094      *  @param dere Enable pin, this pin should be connected to !RE and DE
00095      *  @note uses BufferedSerial
00096      */
00097     RS485(PinName tx, PinName rx, PinName dere);
00098 
00099     /** calculate 8-bit CRC
00100     *  cyclic redundancy check
00101     *  @param addr byte pointer of information to use (typical an byte array)
00102     *  @param len length of byte of information were converting
00103     *  @return the CRC byte
00104     */
00105     static byte crc8 (const byte *addr, byte len);
00106     
00107     /** sendComplemented byte
00108     *  send a byte complemented, repeated
00109     *       only values sent would be (in hex):
00110     *       0F, 1E, 2D, 3C, 4B, 5A, 69, 78, 87, 96, A5, B4, C3, D2, E1, F0
00111     *  @what the byte to complement
00112     */
00113     void sendComplemented (const byte what);
00114     
00115     /** send message
00116     *  cyclic redundancy check
00117     *  @param data the data to be sent through RS485
00118     *  @param length length of the data 
00119     *  @note puts STX at start, ETX at end, and add CRC
00120     */   
00121     void sendMsg (const byte * data, const byte length);
00122     
00123     /** receive message
00124     *  reads serial port and populates data
00125     *  @param data buffer to receive into
00126     *  @param length length of the data 
00127     *  @param timeout clock_mseconds before timing out
00128     *  @return the number of bytes received
00129     *  
00130     */
00131     byte recvMsg (byte * data, const byte length, unsigned long timeout);
00132       
00133 
00134 };
00135 #endif