daq process usb-6008

how to acquire data from this code to process it in another operation in realtime

    % get connected devices
   d = daq.getDevices
   %create session 
    s = daq.createSession('ni')
    %add analog channel  s.addAnalogInputChannel('ID',channel num, 'measurement type')
   s.addAnalogInputChannel('Dev1',0, 'Voltage')

      % set rate of scan  4 scans/second ,  run for 3 seconds
   s.Rate=1000;
   s.DurationInSeconds=30;

v= s.Channels(1);
set(v)
%_____________________________
v.TerminalConfig = ' Differential';
v.Coupling = ' DC';
%start continuous aquisition and plot

h = s.addlistener('DataAvailable', @(src,event) plot(event.TimeStamps, event.Data/.001));
s.NotifyWhenDataAvailableExceeds = 200;
s.startBackground()

Answer 1

[Walter Roberson]

The line

h = s.addlistener('DataAvailable', @(src,event) plot(event.TimeStamps, event.Data/.001));

creates the (anonymous) callback function that will be called when data is available; in this case the data is plotted. You would change that line to do whatever processing you needed.

[mado]

if i want to take the data and store it as a matrix ???

[Walter Roberson]

function storedata(src, event)
  global matrix_index
  global matrix_data
  if isempty(matrix_index); matrix_index = 0; matrix_data = zeros(1024,1)); end
  newdata = event.Data;
  matrix_data(matrix_index+1 : matrix_index + length(newdata)) = newdata;
  matrix_index = matrix_index + length(newdata);
end

except that I would probably rewrite this to use shared variables instead of global variables.

[mado]

executing this function give error message

Not enough input arguments.

[Walter Roberson]

How did you add it as a listener? It should have been something like

h = s.addlistener('DataAvailable', @storedata);

[mado]

that line want give me values that i can process ,i need to have values in a matrix or i can sent it to workspace, i execute it and it gave

h =

event.listener handle
Package: event

Properties:
     Source: {[1x1 daq.ni.Session]}
  EventName: 'DataAvailable'
   Callback: @storedata
    Enabled: 1
  Recursive: 0

Methods, Events, Superclasses

[mado]

any help?

[Walter Roberson]

That line establishes the conditions under which the routine "storedata" will be automatically invoked. It would be the 'storedata' routine that would be responsible for getting the data to where you need it. The code I gave for 'storedata' saves the data to a global variable.

[mado]

 here is all the code i don't understand how to get data to use it in math operation after storing ," storedata" can't be used alone on single line .
how could "storedata" be able to store and restore ??

   %%get connected devices
 d = daq.getDevices
 %create session 
  s = daq.createSession('ni')
  %add analog channel  s.addAnalogInputChannel('ID',channel num, 'measurement type')
  s.addAnalogInputChannel('Dev1',0, 'Voltage')

% set rate of scan 4 scans/second , run for 3 seconds s.Rate=1000; s.DurationInSeconds=30;

v= s.Channels(1); set(v) %_____________________________ %% v.TerminalConfig = ' Differential'; v.Coupling = ' DC';

%% %start continuous aquisition and plot

h = s.addlistener('DataAvailable', @storedata); s.NotifyWhenDataAvailableExceeds = 200; s.startBackground()

[Walter Roberson]

In the routine that needs to access the data, you would add

global matrix_index
global matrix_data

and then the accumulated data so far would be

matrix_data(1:matrix_index)

[mado]

thank you it's working now . i have another problem in

    %  v.TerminalConfig = ' Differential';

when i changed it to singleEnded it don't read real signal idon't know why .

[Walter Roberson]

Single Ended signals use the physical wires differently than Differential. Single Ended use one signal wire (per direction) and a common ground and the signal on the single wire is measured relative to the common ground. Differential use two wires (per direction) and the signal is measured as the difference between the two wires.

[mado]

ok i have done that and both of sinlended and diff are working with labview but here just only differential working

[Walter Roberson]

Could you remind us which MATLAB version you are using?

And to check, is your USB-6008 board from National Instruments ?

[mado]

MATLAB Version: 7.14.0.739 (R2012a) Operating System: Microsoft Windows 7 Version 6.1 (Build 7600) Java Version: Java 1.6.0_17-b04 with Sun Microsystems Inc. Java HotSpot™ 64-Bit Server VM mixed mode .

yes , it's NI board

[Walter Roberson]

Could you show your current code that tries to use single-ended ?

[mado]

just i changed differential to SingleEnded

    %%get connected devices
   d = daq.getDevices
   %create session 
    s = daq.createSession('ni')
    %add analog channel  s.addAnalogInputChannel('ID',channel num, 'measurement type')
    s.addAnalogInputChannel('Dev1',0, 'Voltage')

% set rate of scan  4 scans/second ,  run for 3 seconds
 s.Rate=1000;
 s.DurationInSeconds=30;

v= s.Channels(1);
set(v)
%_____________________________
v.TerminalConfig = ' SingleEnded';
v.Coupling = ' DC';
%start continuous aquisition and plot

h = s.addlistener('DataAvailable', @(src,event) plot(event.TimeStamps, event.Data));
s.NotifyWhenDataAvailableExceeds = 200;
s.startBackground()
 s.wait()
delete (h)
h = s.addlistener('DataAvailable', @storedata);s.NotifyWhenDataAvailableExceeds = 200;
s.startBackground()

global matrix_index
global matrix_data
matrix_data(1:matrix_index)

[Walter Roberson]

As complete speculation: is it possible that you need channel 1 instead of channel 0 for your single ended measurement ?

Answer 2

[mado]

I need to use both of channel 0 and 1 , will it make a difference ?

[Walter Roberson]

Looking at http://www.tau.ac.il/~electro/pdf_files/computer/ni_6008_ADC_manual.pdf

Could you have a look at page 7 and verify your wiring? Differential 0 uses pins 2 and 3, diff 1 uses pins 5 and 6, diff 2 uses pins 8 and 9, diff 3 uses pins 11 and 12; Single ended 0 is pin 2, SE 1 is pin 5, SE 2 is pin 8, SE 3 is pin 11, SE 4 is pin 3, SE 5 is pin 6, SE 6 is pin 9, SE 7 is pin 12.

[mado]

ok, i know that Analog Input Channels 0 to 7—For single-ended measurements, each signal is an analog input voltage channel. For differential measurements, AI 0 and AI 4 are the positive and negative inputs of differential analog input channel 0. The following signal pairs also form differential input channels: <AI 1, AI 5>, <AI 2, AI 6>, and <AI 3,AI 7>.

how to verify writing , i think it's written right

[Walter Roberson]

If you have checked your wiring, then I suggest you open a case with MATLAB technical support. I do not have the software or equipment to go further on this myself.