Questions about using a DIO line for Buffered Triggering

[Tybalt]

I'm writing some software to scan an image using a series of buffers representing a line of the image on the PCI-6602.  So for this, I start with an image size and make a buffer with as many points as are needed to fill out a line on the axis.  Then I am using a DIO line as the trigger to switch locations in the buffer.  So for each line, the system goes to the first point, then triggers, waits, moves, triggers, etc.  To trigger I am sending a simple on-off through the DIO line into the gate of the counter.  This setup is currently working well, but for optimization purposes I need to know some more info.  With that out of the way, my questions:

1.)  In order to do this, I set up a counter on task 1 with edge counting.  Then, I set up a sample clock on task 1 and a DIO line on task 2.  The PCI-6602 has 8 channels, am I right in assuming that I am using 2 channels for this (one for the counter and the other for the sample clock)?

2.)  If so, is there a way to do a trigger based buffered counting without using the second channel, or is the smaple clock the only way to assign a trigger to a counter (not that we need 8 at the moment)?

Thanks in advance!!

[Jason_D]

Tybalt,

According to the product page here I show that the 6602 has 8 counters and 32 DIO lines.  So 1 is DIO and 1 is counter if I understand you correctly.  Therefore you could do 8 tasks just like this one.

[Tybalt]

Thanks for the reply!

So when I create the "sample clock timer" it isn't using a second channel for that?  I'm having a hard time understanding what the sample clock timer is doing in this application.  I feel that it's only purpose is to create the buffer, and signal when to switch the buffer.  Since I am writing digital output in order to switch the buffer, I feel like things like the "rate" don't really mean anything to me.  I'm wondering if there is a better way to do this...

[Jason_D]

Could you possibly post a snippet of the code you are working with or a screenshot.

[Tybalt]

I will include my code, but it's for matlab.  I programmed it before realizing that there is already a package for using nidaqmx in matlab, and its too confusing to go back now :).

        function [obj, error] = initialize(obj, N)
            %Program to initialize the PCI-6602 DAQ card.  Call is made as
            %is shown below:
            %                  [error] = initialize(obj, N)
            %
            %INPUTS
            %obj is the object to initialize.  obj must be a c_PCI6602
            %object.
            %N is the number of buffered spots per line to create.  This
            %will basically be area/step size on stage.
            %
            %OUTPUTS
            %error will be an array of numbers describing the errors in the
            %initialization program.

            if ~libisloaded('myni')
                disp('Matlab: Load nicaiu.dll')
                funclist = loadlibrary('nicaiu.dll','nidaqmx.h','alias','myni');
            end
            disp('Matlab: dll loaded')
            %libfunctionsview('myni')
            %Calling syntax for calllib() is
            %[X1,...,XN]=CALLLIB('LIBNAME','FUNCNAME',ARG1,...,ARGN) and the library
            %has been named myni up there.
           
            %Set Up Pointers-------------------
            obj.read_array = uint32(ones(1,N+1));  %This sets up an array of the size that we will want in the future.
            obj.p_readarray = libpointer('uint32Ptr',obj.read_array);  %makes a pointer to the array for the software to reference.
            obj.empty = [];
            obj.p_empty = libpointer('uint32Ptr',obj.empty);
            obj.sampread = int32(0);
            obj.p_sampread = libpointer('int32Ptr',obj.sampread);
            obj.sampwrit = int32(0);
            obj.p_sampwrit = libpointer('int32Ptr',obj.sampwrit);
           
            %Initialize System-----------------
            %create task 1 (counting)
            task1Name = '';  %type must be character string!
            task1Handle = uint32(1);  %type must be unsigned integer!
            [out1, task1Name, task1Handle]=calllib('myni','DAQmxCreateTask', task1Name, task1Handle);

            %create counter [task1] (type CI count edges) = assign counter to Dev1/ctr0
            cntrl = obj.counter;  %counter definition ex.'Dev1/ctr7'
            startval = uint32(0); %starting value for counting (0 is prob best)
            % NOTE: taskHandle and taskName are defined up there!
            [out2, counter, nameToAssignToChannel]=calllib('myni', 'DAQmxCreateCICountEdgesChan', task1Handle, cntrl, task1Name, obj.DAQmx_Val_Rising, startval, obj.DAQmx_Val_CountUp);

            %create daqmx timing sample clock = assign source to PFI#, task to task1, sample mode to finite, edges to rising, rate to 1000
            rate = double(1000);  %1000 of something.....
            numsamps = uint32(N+1);  %Produce N+1 samples and cut off the first one to leave N samples
            linein = obj.gateport;  %gate of counter 7 is PFI10 ex.'/Dev1/PFI10'
            [out3] = calllib('myni', 'DAQmxCfgSampClkTiming', task1Handle, linein, rate, obj.DAQmx_Val_Rising, obj.DAQmx_Val_FiniteSamps, numsamps);
           
            out4 = -0;  %set values in case if loop is negative
            out5 = -0;
           
            if obj.trigger == 0
                %create task 2 (timing)
                task2Name = '';  %type must be character string!
                task2Handle = uint32(2);  %type must be unsigned integer!
                [out4, task2Name, task2Handle]=calllib('myni','DAQmxCreateTask', task2Name, task2Handle);
               
                %create channel [task2] (type DO digital output) = assign line to Dev1/port0/line7 (this sends to output)
                lineout = obj.triggerport;  %Port where the ext trigger will come from. ex.'Dev1/port0/line3'
                [out5] = calllib('myni', 'DAQmxCreateDOChan', task2Handle, lineout, task2Name, obj.DAQmx_Val_ChanPerLine);
                TH2 = sprintf('%.0f', task2Handle);
                obj.task2 = str2num(TH2);
            end
            error = [out1 out2 out3 out4 out5];
            TH1 = sprintf('%.0f', task1Handle);
            obj.task1 = str2num(TH1);

[Jason_D]

Tybalt,

You have PFI lines 0-7 for DIO only.  You also have the rest of the lines for 8 counters.  You can see the different lines available here on page 32/62.