How can I connect MATLAB with MODBUS RTU gas stream analyzer?

Goal: To send the following message to a MODBUS RTU-enabled X-stream gas analyzer using 16-bit low bit first, using a test message and response to retrieve device serial number (Address 3141-3147, String Output) over RS-232 serial communication port, 16-bit (Low-byte, High-byte) format. The device is an Emerson Process Management XSTREAM X2GP Gas Stream Analyzer that accepts RTU format and either 32-bit Daniel mode or 16-big High or Low (is this same as high byte first or low byte first?).

[Address, Mode, 2xAddress, 2xCoilCount , 2x CRC]

Where:

[ 01, 03, ‘3141’,’0007’,CRC]

Should I use:

   [01 03 49 65 00 07 90 224]

Or

   [01 03 31 41 00 07 210 20] ?

Since for the test file, I want to retrieve the serial number, I expect 7 coils to be returned (3141-3147) correct?

,

Then fwrite(s,messagevector) does not find a response from fread(s, 2) within specified timeout. The following connection setup was used in MATLAB to conform with device settings:

opt.serial=’COM1’;
s=serial(opt.serial);
set(s,’BaudRate’,9600,’DataBits’,8,’StopBits’,1,’Parity’,’even’,Timeout’,3);
set(s,’readasyncmode’,’continous’);

3141 is given as the address code per documentation

Append CRC Code:

N = length(message);
crc = hex2dec('ffff');
polynomial = hex2dec('a001');

for i = 1:N
    crc = bitxor(crc,message(i));
    for j = 1:8
        if bitand(crc,1)
            crc = bitshift(crc,-1);
            crc = bitxor(crc,polynomial);
        else
            crc = bitshift(crc,-1);
        end
    end
end

lowByte = bitand(crc,hex2dec('ff'));
highByte = bitshift(bitand(crc,hex2dec('ff00')),-8);

amsg = message;
amsg(N+1) = lowByte;
amsg(N+2) = highByte;

Answer 1

[Walter Roberson]

My suspicion would be that you should use

[01, 03, typecast(uint16([3141, 7]),'uint8')]

followed by the CRC.

This relies upon the fact that in all currently supported MATLAB versions, the architecture is Intel x86 or x64, both of which are "little-endian", which is the same order that the destination wants.

In decimal this would be [01, 03, 69, 12, 07, 00] followed by the CRC

Answer 2

[Matthew Inoue]

I tried to implement the code that you suggested using

appendcrc([01, 03, typecast(uint16([3141, 7]),'uint8')])

However, MATLAB returned an error in appendcrc using the bitxor (double mixed with integers must have integer values) which I corrected (maybe?) using:

appendcrc(double([01, 03, typecast(uint16([3141, 7]),'uint8')]))

Unfortunately, no message was received. One of my concerns with the existing code is the device is setup for both 32-bit "Daniel" mode and 16-bit Low and High byte first modes (9001 register vs. 6001-6002, for instance). The message sent 16 bits so I'm not quite clear on if my message is correct.

I believe the relevant section of the manual (with attached in-pdf target) is: http://www2.emersonprocess.com/siteadmincenter/PM%20Rosemount%20Analytical%20Documents/PGA_Manual_X-STREAM_XE_201010.pdf#9_HASXEE-IM-HS_X-STREAM%20XE_ModBus%20Commands_e.indd%3A9.2%20Supported%20Functions

[Walter Roberson]

I will try to return to this when my eyes are more rested.

Answer 3

[Camilo Cárdenas]

Hello,

I am trying to carry out a such communication with a x-stream XEGK-Analyzator.

Therefore I would like to ask you if you have reached it and if you ca share some tips and or codes?

regards!