Data acqusition with embedded matlab function. Some functions don't work.

Hi, sorry for so many questions, but I keep getting stuck in making a speed control system for rotating shaft via an encoder and a Pci 1711 acqusition board.

At first I tried making the pulse count through simulink but I found that the program wasn't fast enough and it missed many pulses when the speed wasn't too low ( less than 75 RPM). Then I tried to make a little program in a .m file for measuring pulses and worked well.

Now I want to use that file in the simulink model with an embedded matlab function block, when trying to build the model with the funciton block I find that some functions are not supported for code generation, even though I made a little program for using the analog output and I could build it without problems so I don't know why some functions are available and some are not for code generation.

Any ideas or help about will be vey appreciated.

Thanks in advance.

Alejandro

[ayam mohsen]

please help me ,what version of matlab using with pci-1711,thanks

[Walter Roberson]

Ayam, anything from R14SP1 onward, and R14 itself if you apply the fix I posted the link to in response to your other query.

[ayam mohsen]

thank you walter Roberson ,i read the page

Answer 1

[Azzi Abdelmalek]

Unfortunatly there are some functions which are not allowed with code generation. The only way to find solutions to your problems is to find another way to program whatever you want by usig compatibles codes.

Answer 2

[Kaustubha Govind]

The (Embedded) MATLAB Function Block automatically generates C code from your MATLAB code for accelerated execution, hence only a subset of MATLAB functions are supported for code-generation. If you are simply running the simulation in normal mode (and don't intend to generate code from your model), you can use the coder.extrinsic (formerly eml.extrinsic) directive to call unsupported functions from the block.

However, it may be simpler for you to use the Interpreted MATLAB Function block or a MATLAB S-function block. If you are using toolbox functions like from the Data Acquisition Toolbox, you may find that the toolbox ships with Simulink versions of the functions. For example: Data Acquisition Block Library.

[Alejandro Martín]

Thanks a lot for the answers. My goal is to control the speed of an actual DC motor via matlab, so I want to build a code out of the simulink diagram. I am trying to use an embedded matlab function block because using the real time windows target blocks in simulink the acquisition wasn't fast enough. I saw little programs in the internet which used some data acquisiton functions using the embedded function block but I can't get it working in my program; so I don't know if Matlab doesn't support data acquision via embedded function (although I saw it done in the internet with 'analoguotput' function) or I'm doing something wrong.

Any hint or ideas about a workaround to the problem or a new approach to it will be welcome.

[Kaustubha Govind]

Alejandro: analoguotput doesn't sound like something shipped with MATLAB. Perhaps it is a user-defined function implemented using functions that are supported for code-generation, or might be using coder.extrinsic, or even calls to external libraries invoked using coder.ceval.

[Walter Roberson]

analogoutput is part of the DAQ toolbox

[Azzi Abdelmalek]

the faster way to data aquisition is "xpc target" or using a special card with it's own processor

[Kaustubha Govind]

Walter: Thanks for the correction!

Alejandro: As Walter pointed out, analogoutput is part of the DAQ toolbox, but is not listed amongst the functions supported for code-generation. I'm guessing that the implementations that you've seen declare and use the function with eml.extrinsic (now coder.extrinsic). However, the DAQ Simulink library does ship with the equivalent "Analog Output" block, so you may simply use that.

[Alejandro Martín]

Thanks a lot Kaustubha, Walter and Azzi. I mentioned analoguotput as an example for using in a data acquisition board (I found and example of that in the internet using embedded matlab function), but I tried using an embedded matlab function in the first place because data acquisition in digital input with real time windows target was not fast enough for my application(don't know why because the speeds are low); so I tried with digital input or analog input for counting the pulses when I found out that the functions belonging to data acquisition were not available for code-generation. Now I don't know what to do for acquiring data for making the speed measurements for implementing a control system. Thanks again and sorry for the hassle.

[Kaustubha Govind]

Alejandro: Are you saying that the analogoutput MATLAB function is faster than the Analog Output block in the Simulink library? Since you're using Real-Time Windows Target, would any of the driver blocks from that library work for you: http://www.mathworks.com/products/rtwt/supported/index.html

[Azzi Abdelmalek]

Alejandro, can you tell us what do you mean by fast aquisition? what is your sample time, if it's around 10^-6 s, Real time windows target will not be the good choice, mainly if your machine is a simple PC.

[Alejandro Martín]

Hello again.

Kaustubha, What I meant is quite close to what you wrote, If I make a model in simulink, and use a digitaliput function of the real time windows target library, some pulses are missed. Instead, using the digital input function (the one that belongs to data acquisition toolbox) in a .m file it does not miss pulses (at least for the speeds i'm trying to measure). I wrote the example of analogoutput and analoginput because after trying with digitalinput I made a program for measuring pulses using the analoginput function and attempted to "put" the code in an embedded matlab function block but i found that those functions were not supported for code generation. The same occured with a program using the digitalinput function.

Azzi, sorry for not commenting about the speeds, I want to measure a digital signal with a maximum frequency of, let's say, 120hz. With these speeds I shouldn't be having trouble unsing real time windows target.

Thanks to both of you for your help.

[Kaustubha Govind]

Alejandro: I don't have expertise in the data acquisition area, so there's not much useful advice that I can provide. Perhaps you could contact Tech Support and ask if it is expected that the Simulink Data Acquisition blocks are slower than their MATLAB counterparts?