Question

Hello,

I'm looking for an example of a bash script line to execute a Modbus TCP read request to a slave.

I've searched a lot but I didn't find anything in the documentation.
I need, at initialization, to execute some read/write requests on a Modbus slave and then configure the Modbus_tcp_master.

Thanks

Answer 1

Hi,

You can use the modbus_tcp_test command to gather slave register values through CLI.

EB.

Comments

These Modbus functions are supported:

• 1 (read coils)
• 2 (read inputs)
• 3 (read input registers)
• 4 (read holding registers)
• 5 (write to a single coil)
• 6 (write to a single holding register)
• 15 (write to multiple coils)
• 16 (write to multiple holding registers)

It supports these data types (currently only for reading functions: 1, 2, 3, 4)

• 8-bit signed integer
• 8-bit unsigned integer
• 16-bit signed integer, big-endian (byter order 1, 2)
• 16-bit signed integer, little-endian (byter order 2, 1)
• 16-bit unsigned integer, big-endian (byte order 1, 2)
• 16-bit unsigned integer, little-endian (byte order 2, 1)
• 32-bit signed integer, big-endian (byte order 1, 2, 3, 4)
• 32-bit signed integer, little-endian (byte order 4, 3, 2, 1)
• 32-bit signed integer, byte order 2, 1, 4, 3
• 32-bit signed integer, byte order 3, 4, 1, 2
• 32-bit unsigned integer, big-endian (byte order 1, 2, 3, 4)
• 32-bit unsigned integer, little-endian (byte order 4, 3, 2, 1)
• 32-bit unsigned integer, byte order 2, 1, 4, 3
• 32-bit unsigned integer, byte order 3, 4, 1, 2
• 32-bit IEEE 754 single-precision floating-point number, big-endian (byte order 1, 2, 3, 4)
• 32-bit IEEE 754 single-precision floating-point number, little-endian (byte order 4, 3, 2, 1)
• 32-bit IEEE 754 single-precision floating-point number, byte order 2, 1, 4, 3
• 32-bit IEEE 754 single-precision floating-point number, byte order 3, 4, 1, 2
• HEX
• ASCII

Usage

modbus_tcp_test IP PORT TIMEOUT SLAVE_ID FUNCTION REG_ADDRESS REG_COUNT/VALUE(S) DATA_TYPE

• IP
  • An IPv4 address of the Modbus TCP slave to be tested
• PORT
  • A port (a number in range [0;65535]) which the Modbus TCP slave to be tested is listening to
• TIMEOUT
  • TCP connection timeout, in seconds, in range [1;30]
• SLAVE_ID
  • The slave ID of the Modbus TCP slave to be tested, in range [1;255]
• FUNCTION
  • The Modbus function to be performed: one of 1, 2, 3, 4, 5, 6, 15, 16
• REG_ADDRESS
  • From/to which register address the Modbus function will be performed
• REG_COUNT/VALUE(S)
  • If FUNCTION is 1 or 2:
    • How many coils to read, a number in range [1;2000]
  • If FUNCTION is 3 or 4:
    • How many registers to read, a number in range [1;125]
  • If FUNCTION is 5
    • What coil value to write, either 0 or 65280 (0xFF00)
  • If FUNCTION is 6
    • What register value to write, a number in range [0;65535]
  • If FUNCTION is 15
    • What coil values to write: a sequence of up to 246 8-bit unsigned integers (numbers in range [0;255]) separated by spaces, each representing 8 coils to set
      • For example, 123 54 22 sets 24 coils to values: 01111011 00110110 00010110
  • If FUNCTION is 16
    • What register values to write a sequence of up to 123 16-bit unsigned integers (numbers in range [0;65535]) separated by spaces
• DATA_TYPE
  • Only relevant when reading data from the Modbus TCP slave (functions 1, 2, 3, 4)
  • Must be specified but is ignored when FUNCTION is 5, 6, 15, or 16
  • Specifies how the data retrieved from the Modbus TCP slave will be interpreted
  • For example, we read three registers and received four bytes: AA BB CC DD EE FF
    • When interpreted as HEX, will be interpreted as AA BB CC DD EE FF
    • When interpreted as 16-bit unsigned big-endian integers, will be interpreted as 43707 552455 61183
    • When interpreted as 32-bit unsigned big-endian integers, will be interpreted as 2864434397
      • (not enough to make another number because only two more bytes of data are available)

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Thanks a lot ! It will be very useful.

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Thanks a lot for this post, very useful!

I need function code F22 to write a MASK value. Any suggestion on how to implement this in the RUT955?