I am using this function:
https://es.mathworks.com/help/matlab/import_export/use-events-and-callbacks-for-serial-port-communication.html
function readSerialData(s,~)
data = readline(s);
disp(data);
end
configureCallback(s,"terminator",#readSerialData)
To get data from my connected device. The device receives new data every second or so (50 Bytes), so I get the data displayed on the command line in real time. But I want to actually use this data, but I am not sure how to gather the variables.
I can not see any "data" variable in the workspace, to store it and plot a real time graph (that´s the target)
Thank you in advance :)
Related
My issue involves using the RS-232 Simulink RT blocks.
A model is uploaded to the target PC (xPC) and it transmits and receives data from a variable frequency drive (VFD) that controls a motor. The issue arises on the receiving end when I take data and try to send that data to a display block in my model as a string. Code would be helpful here:
disp = uint8(zeros(1,24));
display = uint8(zeros(1,length(disp)));
cmd = 0;
status = stat_lb;
%% Start-Up
% Initialization Period
if (status == 0 || status == 1)
cmd = 0;
msg = uint8('Start up');
display = [msg uint8(zeros( 1, length(disp)- length(msg) ))];
end
...
%Multiple status cases with unique displays.
...
disp = display
So, here the cmd portion functions as expected. As noted above, I want to display the display string on a display block in my Simulink model. As you can see, though, it is of type uint8, so I need to convert it to type string; however, when I pass it through either the ascii2str Simulink block or just place it in the function call (e.g. display = ascii2str(display)) I get the following error message:
Executing the 'CheckData' command produced the following error: Invalid parameter/value pair arguments
My thought is that this has something to do with the fact that I am using MEX and this function (ascii2str) is not supported. Anyways, I am wondering if anyone knows why I receive this error and if there is anything I can do to resolve it.
Oh, and one last thing: I can get the display to work if I just remove the ascii2str; however, the only problem with this is that the display is in uint8 form and not really helpful. So, if there is any other way that I can decode the uint8 to a string I am all ears.
Thanks!
I have found that there is no support for this feature in Simulink RT. One option is to use external functions, but I found it better for my application to simply output a number and have a table in the simulation that explained what each number meant.
I'm a student learning to use MATLAB. For an assignment, I have to create a simple state machine and collect some results. I'm used to using Verilog/Modelsim, and I'd like to collect data only when the state machine's output changes, which is not necessarily every time/sample period.
Right now I have a model that looks like this:
RequestChart ----> ResponseChart ----> Unit Delay Block --> (Back to RequestChart)
| |
------------------------> Mux --> "To Workspace" Sink Block
I've tried setting the sink block to save as "Array" format, but it only saves 51 values. I've tried setting it to "Timeseries", but it saves tons of zero values.
Can someone give me some suggestions? Like I said, MATLAB is new to me, please let me know if I need to clarify my question or provide more information.
Edit: Here's a screen capture of my model:
Generally Simulink will output a sample at every integration step. If you want to only output data when a particular event occurs -- in this case only when some data changes -- then do the following,
run the output of the state machine into a Detect Change block (from the Logic and Bit Operations library)
run that signal into the trigger port of a Triggered Subsystem.
run the output of the state machine into the data port of the Triggered Subsystem.
inside the triggered subsystem, run the data signal into a To Workspace block.
Data will only be saved at time point that the trigger occurs, i.e. when your data changes.
In your Simulink window, make sure the Relative Tolerance is small so that you can generate many more points in between your start and ending time. Click on the Simulation option at the top of the window, then click on Model Configuration Parameters.
From there, change the Relative Tolerance to something small... like 1e-10. After that, try running your simulation again. You should have a lot more points in your output array that you can now save.
I am trying to use MATLAB in order to know for every single time that a function is called, Matlab returns a specific value.what kind of command i can use that do this for me.
for example for first call return 1000 and for second time return 2000.
Try with the profiler. You will know the number of times that a function is called and the time that has taken.
In the main function:
profile on
To stop it:
profile off
And to show the statistics:
profile viewer
Hope it helps!
I have just recently started to use MATLAB to acquire data off of a data acquisition board and was in need of a function to acquire data continuously (i.e. until I ctrl^C out of the function). To do this I am using the data acquisition toolbox on a 32-bit windows OS.
Based on the documentation in matlab help and a few of the answers on this site, I found that after adding channels to my input handle I should:
set my 'SamplesPerTrigger' to Inf
set the 'TimerPeriod' to some value to trigger the 'TimerFcn'
set the 'TimerFcn' to some subfunction callback which appends data to a persistent variable
Is this a correct way to do this?
My code is as follows:
function acquire_arena_test(samprate,daq_device ,device_ID ,channels, saveroot)
setup.SampleRate = samprate;
setup.DAQdevice = {daq_device, device_ID};
setup.AIChannels = channels;
setup.SaveRoot = {saveroot};
ai = analoginput(setup.DAQdevice{1},setup.DAQdevice{2});
addchannel(ai,[setup.AIChannels]);
set(ai,'SamplesPerTrigger',Inf);
set(ai,'TimerPeriod',0.5);
set(ai,'TimerFcn',{#AcquireData,ai});
start(ai);
while(strcmpi(get(ai,'Running'),'On'))
pause(1)
end
stop(ai);
time = datestr(now,30);
save([saveroot time], 'data');
delete(ai);
clear ai;
function AcquireData(hObject, ~)
persistent totalData;
data = getdata(hObject);
if isempty(totalData)
totalData =data;
else
totalData = [totalData; data];
end
The initial analog input is definitely working properly. I have tried many permutations of giving the AcquireData callback to 'TimerFcn'. The error I receive is
`??? Error using ==> acquire_arena_test>AcquireData
Too many input arguments.
Warning: The TimerFcn callback is being disabled.
To enable the callback, set the TimerFcn property. `
Thanks in advance for any help.
I think the syntax you use for setting up your TimerFcn is wrong. You write
set(ai,'TimerFcn',{#AcquireData,ai});
but this means that your function AcquireData will be called with tree parameters: AcquireData(ai, event, ai) as explained here, which then of course triggers the error message since your AcquireData function only accepts two parameters. Just change your code to
set(ai,'TimerFcn',#AcquireData);
and it should work; the ai object is automatically passed as the first parameter (see the link to the MATLAB documentation above).
Sorry about answering my own question, but I figured it out. The trigger was not needed after all. Using a national instruments board (or a sound card, as it turns out) you can just change the LoggingMode to 'disk' and specify a file to save the .daq (data acquisition toolbox) file to save as with LogFileName. If you want to use the memory on your board, change the mode to disk&Memory. Helpful document:
http://www.mathworks.com/help/toolbox/daq/f12-16658.html
The script below acquires data during the pause, which is as long as you want it to be..
daqreset;
clear all;
ai = analoginput('nidaq','Dev1');
chans = addchannel(ai,0:6);
set(ai,'SamplesPerTrigger',Inf);
set(ai,'SampleRate',1000)
set(ai,'LogToDiskMode','Overwrite')
set(ai,'LogFileName','log.daq')
set(ai,'LoggingMode', 'disk')
start(ai)
pause()
stop(ai)
data = daqread('log.daq');
delete(ai);
Note that you still need to set 'SamplesPerTrigger' to Inf for this to work properly. Thank you to Jonas for his help as well.
I'm developing an iphone app, I need to create a certain size file on filesystem and filled with NO data first, then seek to a offset and write data when get data from somewhere else
How can I do it?
The lseek BSD function is explicitly capable of that.
man lseek:
The lseek() function allows the file offset to be set beyond the end of the
existing end-of-file of the file. If data is later written at this point,
subsequent reads of the data in the gap return bytes of zeros (until data is
actually written into the gap).
NSMutableData or fseek is probably what you want