139 lines
5.5 KiB
C
139 lines
5.5 KiB
C
#ifndef SIMPLE_MODBUS_MASTER_H
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#define SIMPLE_MODBUS_MASTER_H
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// SimpleModbusMasterV10
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/*
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SimpleModbusMaster allows you to communicate
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to any slave using the Modbus RTU protocol.
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To communicate with a slave you need to create a packet that will contain
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all the information required to communicate to the slave.
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Information counters are implemented for further diagnostic.
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These are variables already implemented in a packet.
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You can set and clear these variables as needed.
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The following modbus information counters are implemented:
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requests - contains the total requests to a slave
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successful_requests - contains the total successful requests
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failed_requests - general frame errors, checksum failures and buffer failures
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retries - contains the number of retries
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exception_errors - contains the specific modbus exception response count
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These are normally illegal function, illegal address, illegal data value
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or a miscellaneous error response.
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And finally there is a variable called "connection" that
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at any given moment contains the current connection
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status of the packet. If true then the connection is
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active. If false then communication will be stopped
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on this packet until the programmer sets the connection
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variable to true explicitly. The reason for this is
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because of the time out involved in modbus communication.
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Each faulty slave that's not communicating will slow down
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communication on the line with the time out value. E.g.
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Using a time out of 1500ms, if you have 10 slaves and 9 of them
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stops communicating the latency burden placed on communication
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will be 1500ms * 9 = 13,5 seconds!
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Communication will automatically be stopped after the retry count expires
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on each specific packet.
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All the error checking, updating and communication multitasking
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takes place in the background.
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In general to communicate with to a slave using modbus
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RTU you will request information using the specific
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slave id, the function request, the starting address
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and lastly the data to request.
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Function 1, 2, 3, 4, 15 & 16 are supported. In addition to
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this broadcasting (id = 0) is supported for function 15 & 16.
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Constants are provided for:
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Function 1 - READ_COIL_STATUS
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Function 2 - READ_INPUT_STATUS
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Function 3 - READ_HOLDING_REGISTERS
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Function 4 - READ_INPUT_REGISTERS
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Function 15 - FORCE_MULTIPLE_COILS
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Function 16 - PRESET_MULTIPLE_REGISTERS
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Note:
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The Arduino serial ring buffer is 128 bytes or 64 registers.
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Most of the time you will connect the Arduino using a MAX485 or similar.
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In a function 3 or 4 request the master will attempt to read from a
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slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
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and two BYTES CRC the master can only request 122 bytes or 61 registers.
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In a function 16 request the master will attempt to write to a
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slave and since 9 bytes is already used for ID, FUNCTION, ADDRESS,
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NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
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118 bytes or 59 registers.
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Note:
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Using a USB to Serial converter the maximum bytes you can send is
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limited to its internal buffer which differs between manufactures.
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Since it is assumed that you will mostly use the Arduino to connect without
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using a USB to Serial converter the internal buffer is set the same as the
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Arduino Serial ring buffer which is 128 bytes.
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*/
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#include "Arduino.h"
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#define READ_COIL_STATUS 1 // Reads the ON/OFF status of discrete outputs (0X references, coils) in the slave.
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#define READ_INPUT_STATUS 2 // Reads the ON/OFF status of discrete inputs (1X references) in the slave.
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#define READ_HOLDING_REGISTERS 3 // Reads the binary contents of holding registers (4X references) in the slave.
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#define READ_INPUT_REGISTERS 4 // Reads the binary contents of input registers (3X references) in the slave. Not writable.
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#define FORCE_MULTIPLE_COILS 15 // Forces each coil (0X reference) in a sequence of coils to either ON or OFF.
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#define PRESET_MULTIPLE_REGISTERS 16 // Presets values into a sequence of holding registers (4X references).
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typedef struct
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{
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// specific packet info
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unsigned char id;
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unsigned char function;
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unsigned int address;
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// For functions 1 & 2 data is the number of points
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// For functions 3, 4 & 16 data is the number of registers
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// For function 15 data is the number of coils
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unsigned int data;
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unsigned int* register_array;
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// modbus information counters
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unsigned int requests;
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unsigned int successful_requests;
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unsigned int failed_requests;
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unsigned int exception_errors;
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unsigned int retries;
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// connection status of packet
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unsigned char connection;
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bool *connectionValid;
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bool *valueValid;
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}Packet;
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typedef Packet* packetPointer;
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// function definitions
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void modbus_update();
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void modbus_construct(Packet *_packet,
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unsigned char id,
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unsigned char function,
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unsigned int address,
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unsigned int data,
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unsigned int* register_array);
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void modbus_configure(HardwareSerial* SerialPort,
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long baud,
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unsigned char byteFormat,
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unsigned int _timeout,
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unsigned int _polling,
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unsigned char _retry_count,
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unsigned char _TxEnablePin,
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Packet* _packets,
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unsigned int _total_no_of_packets);
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#endif |