Aaron Allar / RS485

A basic library for RS485 communication

Dependencies:   BufferedSerial

Dependents:   mbed_blinko

RS485.h@4:6a8a69b660c2, 2017-05-21 (annotated)

Committer:
Allar
Date:
Sun May 21 20:41:37 2017 +0000
Revision:
4:6a8a69b660c2
Parent:
3:9af77202cc27 
Published

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Allar 0:dccd2df6a07c 1
Allar 0:dccd2df6a07c 2 /**
Allar 0:dccd2df6a07c 3 * @file RS485.h
Allar 0:dccd2df6a07c 4 * @brief RS485 protocol - using half duplex method
Allar 0:dccd2df6a07c 5 * @author Aaron Allar
Allar 0:dccd2df6a07c 6 * @version 1.0
Allar 0:dccd2df6a07c 7 * @see
Allar 0:dccd2df6a07c 8 *
Allar 0:dccd2df6a07c 9 * based on this method https://www.gammon.com.au/forum/?id=11428
Allar 0:dccd2df6a07c 10 *
Allar 0:dccd2df6a07c 11 * Can send from 1 to 255 bytes from one node to another with:
Allar 0:dccd2df6a07c 12 *
Allar 0:dccd2df6a07c 13 * Packet start indicator (STX)
Allar 0:dccd2df6a07c 14 * Each data byte is doubled and inverted to check validity
Allar 0:dccd2df6a07c 15 * Packet end indicator (ETX)
Allar 0:dccd2df6a07c 16 * Packet CRC (checksum)
Allar 0:dccd2df6a07c 17 */
Allar 0:dccd2df6a07c 18
Allar 0:dccd2df6a07c 19
Allar 0:dccd2df6a07c 20
Allar 0:dccd2df6a07c 21 #ifndef RS485_H
Allar 0:dccd2df6a07c 22 #define RS485_H
Allar 1:f7cead04d73e 23
Allar 1:f7cead04d73e 24 #include "BufferedSerial.h"
Allar 0:dccd2df6a07c 25 #include "mbed.h"
Allar 0:dccd2df6a07c 26
Allar 4:6a8a69b660c2 27 /** RS485 Library
Allar 0:dccd2df6a07c 28 *
Allar 4:6a8a69b660c2 29 * Can send from 1 to 255 bytes from one node to another with:
Allar 4:6a8a69b660c2 30 *
Allar 4:6a8a69b660c2 31 * Packet start indicator (STX)
Allar 4:6a8a69b660c2 32 * Each data byte is doubled and inverted to check validity
Allar 4:6a8a69b660c2 33 * Packet end indicator (ETX)
Allar 4:6a8a69b660c2 34 * Packet CRC (checksum)
Allar 4:6a8a69b660c2 35 *
Allar 4:6a8a69b660c2 36 * Using MAX485 modules or the MAX485 CSA+
Allar 0:dccd2df6a07c 37 *
Allar 0:dccd2df6a07c 38 * Example:
Allar 0:dccd2df6a07c 39 * @code
Allar 0:dccd2df6a07c 40 * #include "mbed.h"
Allar 0:dccd2df6a07c 41 * #include <RS485.h>
Allar 0:dccd2df6a07c 42 * Serial pc(USBTX, USBRX);
Allar 3:9af77202cc27 43 * RS485 RS485(PC_10,PC_11,PB_3); // Tx, Rx , !RE and DE MAX485 pin
Allar 0:dccd2df6a07c 44 *
Allar 3:9af77202cc27 45 * DigitalOut ho(PB_3); // this pin should be connected to !RE and DE
Allar 0:dccd2df6a07c 46 * typedef uint8_t byte;
Allar 0:dccd2df6a07c 47 *
Allar 0:dccd2df6a07c 48 * byte regvalue[9];
Allar 0:dccd2df6a07c 49 * byte data[9] = {0x01,0x04,0x00,0x48,0x00,0x02,0xf1,0xdd};//your data
Allar 0:dccd2df6a07c 50 * int main()
Allar 0:dccd2df6a07c 51 * {
Allar 0:dccd2df6a07c 52 * pc.printf("main\n");
Allar 0:dccd2df6a07c 53 * while(1) {
Allar 0:dccd2df6a07c 54 * pc.printf("Starting\n");
Allar 3:9af77202cc27 55 * ho = 1; // Enable sending on MAX485
Allar 0:dccd2df6a07c 56 * RS485.sendMsg(data,sizeof(data));
Allar 0:dccd2df6a07c 57 * wait_ms(600); // Must wait for all the data to be sent
Allar 3:9af77202cc27 58 * ho = 0; // Enable receiving on MAX485
Allar 0:dccd2df6a07c 59 * pc.printf("Getting data\n");
Allar 0:dccd2df6a07c 60 * if(RS485.readable() >0){
Allar 0:dccd2df6a07c 61 * memset(regvalue,0,sizeof(regvalue));
Allar 0:dccd2df6a07c 62 * wait_ms(200);
Allar 0:dccd2df6a07c 63 * RS485.recvMsg(regvalue,sizeof(data),500);
Allar 0:dccd2df6a07c 64 * wait_ms(200);
Allar 0:dccd2df6a07c 65 * for (int count = 0; count < 9; count++) {
Allar 0:dccd2df6a07c 66 * pc.printf("%X - ", regvalue[count]);
Allar 0:dccd2df6a07c 67 * }
Allar 0:dccd2df6a07c 68 * }else printf("No Data\n");
Allar 0:dccd2df6a07c 69 * printf("Done\n");
Allar 0:dccd2df6a07c 70 * wait_ms(1000);
Allar 0:dccd2df6a07c 71 * }
Allar 0:dccd2df6a07c 72 * }
Allar 0:dccd2df6a07c 73 * @endcode
Allar 0:dccd2df6a07c 74 */
Allar 0:dccd2df6a07c 75
Allar 0:dccd2df6a07c 76
Allar 0:dccd2df6a07c 77 /**
Allar 0:dccd2df6a07c 78 * @class RS485
Allar 4:6a8a69b660c2 79 * @communicating
Allar 0:dccd2df6a07c 80 */
Allar 0:dccd2df6a07c 81
Allar 0:dccd2df6a07c 82 class RS485 : public BufferedSerial
Allar 0:dccd2df6a07c 83 {
Allar 0:dccd2df6a07c 84 private:
Allar 0:dccd2df6a07c 85 typedef unsigned int word;
Allar 0:dccd2df6a07c 86 typedef uint8_t byte;
Allar 0:dccd2df6a07c 87 typedef uint8_t boolean;
Allar 0:dccd2df6a07c 88 typedef void (*voidFuncPtr)(void);
Allar 0:dccd2df6a07c 89
Allar 0:dccd2df6a07c 90 public:
Allar 0:dccd2df6a07c 91 /** Create a BufferedSerial port, connected to the specified transmit and receive pins
Allar 0:dccd2df6a07c 92 * @param tx Transmit pin
Allar 0:dccd2df6a07c 93 * @param rx Receive pin
Allar 3:9af77202cc27 94 * @param dere Enable pin, this pin should be connected to !RE and DE
Allar 0:dccd2df6a07c 95 * @note uses BufferedSerial
Allar 0:dccd2df6a07c 96 */
Allar 0:dccd2df6a07c 97 RS485(PinName tx, PinName rx, PinName dere);
Allar 0:dccd2df6a07c 98
Allar 0:dccd2df6a07c 99 /** calculate 8-bit CRC
Allar 0:dccd2df6a07c 100 * cyclic redundancy check
Allar 2:2701d79eba7c 101 * @param addr byte pointer of information to use (typical an byte array)
Allar 1:f7cead04d73e 102 * @param len length of byte of information were converting
Allar 0:dccd2df6a07c 103 * @return the CRC byte
Allar 0:dccd2df6a07c 104 */
Allar 0:dccd2df6a07c 105 static byte crc8 (const byte *addr, byte len);
Allar 0:dccd2df6a07c 106
Allar 0:dccd2df6a07c 107 /** sendComplemented byte
Allar 0:dccd2df6a07c 108 * send a byte complemented, repeated
Allar 0:dccd2df6a07c 109 * only values sent would be (in hex):
Allar 0:dccd2df6a07c 110 * 0F, 1E, 2D, 3C, 4B, 5A, 69, 78, 87, 96, A5, B4, C3, D2, E1, F0
Allar 0:dccd2df6a07c 111 * @what the byte to complement
Allar 0:dccd2df6a07c 112 */
Allar 0:dccd2df6a07c 113 void sendComplemented (const byte what);
Allar 0:dccd2df6a07c 114
Allar 0:dccd2df6a07c 115 /** send message
Allar 0:dccd2df6a07c 116 * cyclic redundancy check
Allar 1:f7cead04d73e 117 * @param data the data to be sent through RS485
Allar 1:f7cead04d73e 118 * @param length length of the data
Allar 0:dccd2df6a07c 119 * @note puts STX at start, ETX at end, and add CRC
Allar 0:dccd2df6a07c 120 */
Allar 0:dccd2df6a07c 121 void sendMsg (const byte * data, const byte length);
Allar 0:dccd2df6a07c 122
Allar 0:dccd2df6a07c 123 /** receive message
Allar 0:dccd2df6a07c 124 * reads serial port and populates data
Allar 1:f7cead04d73e 125 * @param data buffer to receive into
Allar 1:f7cead04d73e 126 * @param length length of the data
Allar 1:f7cead04d73e 127 * @param timeout clock_mseconds before timing out
Allar 1:f7cead04d73e 128 * @return the number of bytes received
Allar 0:dccd2df6a07c 129 *
Allar 0:dccd2df6a07c 130 */
Allar 0:dccd2df6a07c 131 byte recvMsg (byte * data, const byte length, unsigned long timeout);
Allar 0:dccd2df6a07c 132
Allar 0:dccd2df6a07c 133
Allar 0:dccd2df6a07c 134 };
Allar 0:dccd2df6a07c 135 #endif