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Reading data from Modbus RTU device (Kamstrup Multical 603) with CR6 logger

ipantev Jan 5, 2021 08:55 AM

Hi all,

As part of a project, I am trying to use a CR6 datalogger to read data from a Modbus RTU device (Kamstrup Multical 603 with a HC-003-67 Modbus RTU module). 


- Modbus slave address = 93

- Communication speed = 19200baud

- Parity/stop = Even parity/ One stop bit

- Default datagram (register addressing on the RTU)


For now I am trying to read registers 1-82 (inclusive), which are made up of 32bit IEEE Float values (i.e. 2 registers make up one value - 1&2, 3&4... 81&82). The hex addresses for these are in the range 0000 to 0051. Alternatively I can use other registers from the datagram which are defined in UINT 16bit.


I'm using a 2-wire shielded 24-awg cable and this is connected to the Data A- / B+ / GND ports on the Modbus RTU module (see link). On the CR6 I am using the COM1/2 pair as well as the corresponding GND.


 Below are the relevant parts of the cr6 program I've been trying:

'Modbus communication with Kamstrup Multical603 with HC-003-67 RTU
Public Modbus_data(81) 'Data from the default registers in the Logger
Public Modbus_Result
Public Modbus_Bool

 The code below is executed in the main scan loop:

'Read information over Modbus from the Kamstrup Multical 603 reader
SerialOpen (ComC1,19200,18,200,0,4) 'Set bit parity and baud rate to correct values ()
ModbusMaster (Modbus_Result, ComC1, 19200, 93, 3, Modbus_data(),1,40,3,200)
SerialClose (ComC1)


Unfortunately, there is no data read into the Modbus_data array (all remain zeros) and the Modbus_Result variable is incremented by 1 at each scan interval indicating a communication timeout.

Does anyone have an idea how to proceed from here?

Links with info:

Multical 603 energy meter here

Additional Modbus RTU module HC-003-67 and datagram here

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