Gustavo González / SimpleModbusSlave

SimpleModbusSlave allows you to communicate to any slave using the Modbus RTU protocol. The crc calculation is based on https://os.mbed.com/users/jpelletier/code/CRC/ The functions implemented are functions 3 and 16. read holding registers and preset multiple registers of the Modbus RTU Protocol. This implementation DOES NOT fully comply with the Modbus specifications.

SimpleModbusSlave.h@1:85e226914fb7, 2017-10-25 (annotated)

Committer:
gugani
Date:
Wed Oct 25 10:38:11 2017 +0000
Revision:
1:85e226914fb7
Parent:
0:7c5265097fd2 
Initial commit

Who changed what in which revision?

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gugani 0:7c5265097fd2 1 #ifndef SIMPLE_MODBUS_SLAVE_H
gugani 0:7c5265097fd2 2 #define SIMPLE_MODBUS_SLAVE_H
gugani 0:7c5265097fd2 3
gugani 0:7c5265097fd2 4 /*
gugani 0:7c5265097fd2 5 SimpleModbusSlave allows you to communicate
gugani 0:7c5265097fd2 6 to any slave using the Modbus RTU protocol.
gugani 0:7c5265097fd2 7
gugani 0:7c5265097fd2 8 The crc calculation is based on the work published
gugani 0:7c5265097fd2 9 by jpmzometa at
gugani 0:7c5265097fd2 10 http://sites.google.com/site/jpmzometa/arduino-mbrt
gugani 0:7c5265097fd2 11
gugani 0:7c5265097fd2 12 By Juan Bester : bester.juan@gmail.com
gugani 0:7c5265097fd2 13
gugani 0:7c5265097fd2 14 The functions implemented are functions 3 and 16.
gugani 0:7c5265097fd2 15 read holding registers and preset multiple registers
gugani 0:7c5265097fd2 16 of the Modbus RTU Protocol, to be used over the Arduino serial connection.
gugani 0:7c5265097fd2 17
gugani 0:7c5265097fd2 18 This implementation DOES NOT fully comply with the Modbus specifications.
gugani 0:7c5265097fd2 19
gugani 0:7c5265097fd2 20 Specifically the frame time out have not been implemented according
gugani 0:7c5265097fd2 21 to Modbus standards. The code does however combine the check for
gugani 0:7c5265097fd2 22 inter character time out and frame time out by incorporating a maximum
gugani 0:7c5265097fd2 23 time out allowable when reading from the message stream.
gugani 0:7c5265097fd2 24
gugani 0:7c5265097fd2 25 These library of functions are designed to enable a program send and
gugani 0:7c5265097fd2 26 receive data from a device that communicates using the Modbus protocol.
gugani 0:7c5265097fd2 27
gugani 0:7c5265097fd2 28 SimpleModbusSlave implements an unsigned int return value on a call to modbus_update().
gugani 0:7c5265097fd2 29 This value is the total error count since the slave started. It's useful for fault finding.
gugani 0:7c5265097fd2 30
gugani 0:7c5265097fd2 31 This code is for a Modbus slave implementing functions 3 and 16
gugani 0:7c5265097fd2 32 function 3: Reads the binary contents of holding registers (4X references)
gugani 0:7c5265097fd2 33 function 16: Presets values into a sequence of holding registers (4X references)
gugani 0:7c5265097fd2 34
gugani 0:7c5265097fd2 35 All the functions share the same register array.
gugani 0:7c5265097fd2 36
gugani 0:7c5265097fd2 37 Exception responses:
gugani 0:7c5265097fd2 38 1 ILLEGAL FUNCTION
gugani 0:7c5265097fd2 39 2 ILLEGAL DATA ADDRESS
gugani 0:7c5265097fd2 40 3 ILLEGAL DATA VALUE
gugani 0:7c5265097fd2 41
gugani 0:7c5265097fd2 42 Note:
gugani 0:7c5265097fd2 43 The Arduino serial ring buffer is 128 bytes or 64 registers.
gugani 0:7c5265097fd2 44 Most of the time you will connect the arduino to a master via serial
gugani 0:7c5265097fd2 45 using a MAX485 or similar.
gugani 0:7c5265097fd2 46
gugani 0:7c5265097fd2 47 In a function 3 request the master will attempt to read from your
gugani 0:7c5265097fd2 48 slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
gugani 0:7c5265097fd2 49 and two BYTES CRC the master can only request 122 bytes or 61 registers.
gugani 0:7c5265097fd2 50
gugani 0:7c5265097fd2 51 In a function 16 request the master will attempt to write to your
gugani 0:7c5265097fd2 52 slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
gugani 0:7c5265097fd2 53 NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
gugani 0:7c5265097fd2 54 118 bytes or 59 registers.
gugani 0:7c5265097fd2 55
gugani 0:7c5265097fd2 56 Using the FTDI converter ic the maximum bytes you can send is limited
gugani 0:7c5265097fd2 57 to its internal buffer which is 60 bytes or 30 unsigned int registers.
gugani 0:7c5265097fd2 58
gugani 0:7c5265097fd2 59 Thus:
gugani 0:7c5265097fd2 60
gugani 0:7c5265097fd2 61 In a function 3 request the master will attempt to read from your
gugani 0:7c5265097fd2 62 slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
gugani 0:7c5265097fd2 63 and two BYTES CRC the master can only request 54 bytes or 27 registers.
gugani 0:7c5265097fd2 64
gugani 0:7c5265097fd2 65 In a function 16 request the master will attempt to write to your
gugani 0:7c5265097fd2 66 slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
gugani 0:7c5265097fd2 67 NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
gugani 0:7c5265097fd2 68 50 bytes or 25 registers.
gugani 0:7c5265097fd2 69
gugani 0:7c5265097fd2 70 Since it is assumed that you will mostly use the Arduino to connect to a
gugani 0:7c5265097fd2 71 master without using a USB to Serial converter the internal buffer is set
gugani 0:7c5265097fd2 72 the same as the Arduino Serial ring buffer which is 128 bytes.
gugani 0:7c5265097fd2 73
gugani 0:7c5265097fd2 74 The functions included here have been derived from the
gugani 0:7c5265097fd2 75 Modbus Specifications and Implementation Guides
gugani 0:7c5265097fd2 76
gugani 0:7c5265097fd2 77 http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
gugani 0:7c5265097fd2 78 http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
gugani 0:7c5265097fd2 79 http://www.modbus.org/docs/PI_MBUS_300.pdf
gugani 0:7c5265097fd2 80 */
gugani 0:7c5265097fd2 81
gugani 0:7c5265097fd2 82
gugani 0:7c5265097fd2 83
gugani 0:7c5265097fd2 84 // function definitions
gugani 0:7c5265097fd2 85 void modbus_configure(long baud, char _slaveID, char _TxEnablePin, unsigned int _holdingRegsSize, unsigned char _lowLatency);
gugani 0:7c5265097fd2 86 unsigned int modbus_update(unsigned int *holdingRegs);
gugani 1:85e226914fb7 87 unsigned int newdatarec(void);
gugani 1:85e226914fb7 88 unsigned int newdatasent(void);
gugani 0:7c5265097fd2 89
gugani 0:7c5265097fd2 90 #endif