How to set Query Instrument Block parameters in proper format?

Hello,

I'm trying to remote control Keysight DC Electronic Load N3300A with Simulink via GPIB interface, and use GPIB-USB-HS+ board from NI to connect the instrument with my PC. I want to set the instrument to be in CC mode and sink 1.25A of current, and then send the measured current data back to my Simulink model. There is no problem that I control it with sending command through Test & Measuring Tool or run in Matlab script, Here are the commands in Matlab scrip:

C1 = gpib('ni',0,3); % Board index=0, Address=3

fopen(C1);

C1.EOSMode = 'read&write';

C1.EOSCharCode = 'LF';

fprintf(C1,'CHAN 2'); % Using channel 2

fprintf(C1,'INPUT OFF');

fprintf(C1,'FUNC CURR'); % Set CC mode

fprintf(C1,'CURR:RANG MIN'); % Set low current range

fprintf(C1,'CURR 1.25'); % Set current sink to be 1.25A

fprintf(C1,'INPUT ON');

fprintf(C1,'MEAS:CURR?'); % mearsure the input current

CurData = fscanf(C1)

fclose(C1);

delete(C1);

clear C1;

CurVal = str2double(CurData);

And thus I use the same settings and commands in Query Instrument Block in Simulink, but there is no response from the instrument. I am not sure the parameters I set in the block are in correct format, here are my settings:

Parameters

　Block Sample Time: 1

Hardware Configuration

　Timeout: 10

　Buffer Size: 512

　Interface: GPIB

　Board Vendor: National Instruments

　Board index: 0

　Primary Address: 3

　Secondary Address: 0

Instrument Initialization

　Send string: 'CHAN 2 ; INPUT OFF ; FUNC CURR ; CURR:RANG MIN ; CURR 1.25 ; :INPUT ON'

　*I had also tried selecting Execute function, but not sure if I have to type fprintf or fprintf('CHAN 2 ; INPUT OFF ; FUNC CURR ; CURR:RANG MIN ; CURR 1.25 ; :INPUT ON').

Query

　Query command: 'MEAS:CURR?'

　Data format: ASCII

　ASCII format string: '%c' (I'd also tried '%1.3f')

　Byte order: Little Endian

Checked "Remove any additional bytes from input buffer"

After initial response: Repeat query for new data

In addition, since I can obtain the instrument data via Matlab script and store it in workspace, is there any method to run a m-file in each time step in Simulink? I would like to import the measured data into my Simulink model and apply Simulink Destop Real-Time to do the real-time processing. However, I can't write the commands into Matlab Function Block because it exists an error "The 'gpib' class does not support code generation." and also don't know if callbacks can run the script automatically in every time step.

Any tips about setting Query Instrument Block or importing data from m-file would be greatly appreciated!

Regards,

Joanne

Answer 1

[Jan Houska]

Hi Joanne,

you cannot use gpib object with SImulink Desktop Real-Time in External mode because it does not support code generation. However, you can still use the object with SImulink Desktop Real-Time in Normal mode. To do that, please put the Real-Time Sync block into your model and run the model from the SIMULATION toolstrip tab (as opposed to the DESKTOP REAL-TIME tab).

Good Luck, Jan

[Pin An Lin]

Hi Jan,

Thank you for the reply. I know the gpib object can be only used in normal and accelerator mode. And I haven't applied Real-Time Sync block because I would like to first comfirm my PC can obtain the correct response via Query Instrument block. However, I didn't get any response from the instrument and always get 0A even there is no real-time processing.

Regards,

Joanne

Answer 2

[Andrei]

Joanne,

If you're using the gpib code within a MATLAB Function block, since it does not support code generation you need to declare gpib (and the gpib related functions you're using, i.e. fopen, etc.) with coder.extrinsic ( https://www.mathworks.com/help/simulink/function-definition.html ). Within a MATLAB Function block for setting/getting gbib property values you would also need to use the set and get functions rather than dot notation.

Another option would be to call your MATLAB function via an Interpreted MATLAB Function block ( https://www.mathworks.com/help/simulink/slref/interpretedmatlabfunction.html ).

For troubleshooting the behavior you are seeing with the Query Instrument block, consider contacting MathWorks support.

Andrei