RTSI Trigger (DAQmx & C++)

Dear Reader
I tried to Synchronize the Starting of the output of two NI cards using the RTSI bus.
I wrote the following code - but the slave-device doesn't start.
Could anyone please tell me what's maybe missing?
Pascal
//PCIe 6259 (Dev1): AO master, export StartTrigger to RTSI0
    error = DAQmxCreateTask("",&ao6259TaskHandle);
    error = DAQmxCreateAOVoltageChan(ao6259TaskHandle, "Dev1/ao0", "", -5.0, 5.0, DAQmx_Val_Volts, "");
    error = DAQmxCfgSampClkTiming(ao6259TaskHandle, "OnboardClock", 1000.0, DAQmx_Val_Rising, DAQmx_Val_FiniteSamps, 10000);
    error = DAQmxExportSignal(ao6259TaskHandle, DAQmx_Val_StartTrigger, "RTSI0");
    error = DAQmxWriteRaw(ao6259TaskHandle, 10000, false, 10.0, dataBuffer, NULL, NULL);
//PCI 6733 (Dev2): Slave device (only triggered)
    error = DAQmxCreateTask("", &ao6733TaskHandle);
    error = DAQmxCreateAOVoltageChan(ao6733TaskHandle, "Dev2/ao0", "", -5.0, 5.0, DAQmx_Val_Volts, "");
    error = DAQmxCfgSampClkTiming(ao6733TaskHandle, "OnboardClock", 1000.0, DAQmx_Val_Rising, DAQmx_Val_FiniteSamps, 10000);
    error = DAQmxCfgDigEdgeStartTrig(ao6733TaskHandle, "RTSI0", DAQmx_Val_Rising);
    error = DAQmxWriteRaw(ao6733TaskHandle, 10000, false, 10.0, dataBuffer, NULL, NULL);
    error = DAQmxStartTask(ao6259TaskHandle);

Hello Pascal,
I took a look at your code and it ran perfectly on my machine. As I already told you: You need to start the slave task in advance!
I just added the red line of code.
#include <ansi_c.h>
//#include "stdafx.h"
//#include "windows.h"
#include <NIDAQmx.h>
#include <math.h>
#define false 0
#define true 1
int main(int argc, char* argv[])
    // PCI 6251 master, PCI 6733 as slave
    int32 error = 0;
    TaskHandle ao6251TaskHandle = 0;
    TaskHandle triggerHandle = 0;
    TaskHandle aiTaskHandle = 0;
    TaskHandle ao6733TaskHandle = 0;
    char errBuff[2048]={'\0'};
    const int32 nPoints = 10000;
    short dataBuffer[10000];
    float64 dummyBuffer[10];
    uInt32 digiData[10]={0xFFFFFFFF,2,4,8,16,32,64,128,256,0xFFFFFFFF};
    // Init analog dataBuffer
    int i=0;
    for (i=0; i<nPoints; i++) {
        dataBuffer[i] = floor(15000.0*sin(((double)i)/707.0)+15001.0);
    //PCI 6251 (Dev4): AO master, export StartTrigger to RTSI0
    error = DAQmxCreateTask("",&ao6733TaskHandle);
    error = DAQmxCreateTask("",&ao6251TaskHandle);
    error = DAQmxCreateAOVoltageChan(ao6251TaskHandle, "Dev4/ao0", "", -5.0, 5.0, DAQmx_Val_Volts, "");
    error = DAQmxCfgSampClkTiming(ao6251TaskHandle, "OnboardClock", 1000.0, DAQmx_Val_Rising, DAQmx_Val_FiniteSamps, 10000);
    error = DAQmxExportSignal (ao6251TaskHandle, DAQmx_Val_StartTrigger, "RTSI0");
    error = DAQmxWriteRaw(ao6251TaskHandle, 10000, false, 10.0, dataBuffer, NULL, NULL);
//PCI 6733 (Dev1): Slave device (only triggered)
error = DAQmxCreateAOVoltageChan(ao6733TaskHandle, "Dev1/ao0", "", -5.0, 5.0, DAQmx_Val_Volts, "");
error = DAQmxCfgSampClkTiming (ao6733TaskHandle, "OnboardClock", 1000.0, DAQmx_Val_Rising, DAQmx_Val_FiniteSamps, 10000);
error = DAQmxCfgDigEdgeStartTrig (ao6733TaskHandle, "RTSI0", DAQmx_Val_Rising);
error = DAQmxWriteRaw (ao6733TaskHandle, 10000, false, 10.0, dataBuffer, NULL, NULL);
DAQmxGetExtendedErrorInfo(errBuff,2048);
error = DAQmxStartTask(ao6733TaskHandle);
error = DAQmxStartTask(ao6251TaskHandle);
  getchar();
    DAQmxClearTask(ao6733TaskHandle);
    DAQmxClearTask(ao6251TaskHandle);
    return 0;
Hope this helps, regards, C.L.

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TheRealMichaelJordan wrote:
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Attachments:
Triggered with RTSI from DAQ.vi ‏63 KB
camera configuration.jpg ‏218 KB

Thanks a lot, the post helped.
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Attachments:
camera configuration.jpg ‏168 KB
External Camera Trigger(SMB).vi ‏57 KB

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http://decibel.ni.com/content/docs/DOC-8473
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Attachments:
Gen Gated Dig Pulse Train-Continuous.vi ‏38 KB

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I'm reading a continuous stream of CAN-messages with a CAN-Object. I'm creating occurences and reading multiple samples in a while loop.
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I am using following code to continuously acquire data from 2 channels, then export to a text file for analysis with Execel or Origin. The data file should contain four columns:
t1 Y1 t2 Y2
I know it is convenient to use Write Measurement File express VI, but since this express VI open and close file in each loop execution, I prefer to use low-level File I/O functions to save computer resources (I need to reserve resources for image acquisition and analyses).
The following attached VI just show the overall frame of the code, but is not executable now. I hope to get some suggestions from this forum to finish it.
Here, I have two main questions, thank you in advance if you can provide hints to any of them.
(1) How to get correct t0 and dt values for the waveform data
I am using 25Hz pulse signal to externally trigger DAQmx through PFI0. I set 100Hz for the rate input of the DAQmx timing VI since LabVIEW help says "If you use an external source for the Sample Clock, set this input to the
maximum expected rate of that clock. " .
When I use Write Measurement File express VI, I found in the resulting text file, the dt is 0.01 instead of 0.04, i.e., the value of dt in the waveform data is not determined by external PFI0 signal, but by the rate input for the DAQmx timing VI. Also, I found t0 does not always start from zero. However, from the display of data plot, I am sure the acquisition is at 25Hz.
Some people in this forum ever told me to use Get Waveform Component and Build waveform functions to manually rebuild the waveform data in order to get correct t0 and dt. I tried and no luck to succeed. Anyone can give me more detailed hints?
(2) How to write data of 'NChan NSample' at one time in a loop
I have two channel DAQmx, and for each channel there are several data points. I plan to use following method to export data:
Suppose in one loop DAQmx Read VI read 10 samples from each channel, so I assume I will get four arrays of 10 elements:
t_channel_1, Y_channel_1, t_channel_2, Y_channel_2.
Then I use a loop structure of N=10 to concatenate t1, tab,Y1,tab, t2,tab, Y2,return in 'element by element' mode, i.e., do 10 times of string concatenate and write to text file.
I don't know whether above method is effective. Anyone can advise a better one?
(3) Convert from timestamp to elapsed time in milisecond
In the final text file, the time column should be the values of elapsed time in milisecond since the start of acquisition. So, I think I need to get the timestamp of the first data point so that for later data points I can use Elapsed Time express VI to extract elapsed time in milisecond. However, I don't know how to get the timestamp at the starting of acquisition. Please advise if you know it.
Sincerely,
Dejun
Message Edited by Dejun on 08-30-2007 10:34 AM
Attachments:
code.jpg ‏86 KB
code.vi ‏49 KB

tbob wrote:
Ravens Fan:
Read his post again:
"I am using 25Hz pulse signal to externally trigger DAQmx through PFI0. I set 100Hz for the rate input of the DAQmx timing VI since LabVIEW help says "If you use an external source for the Sample Clock, set this input to the maximum expected rate of that clock. " .
When I use Write Measurement File express VI, I found in the resulting text file, the dt is 0.01 instead of 0.04, i.e., the value of dt in the waveform data is not determined by external PFI0 signal, but by the rate input for the DAQmx timing VI. Also, I found t0 does not always start from zero. However, from the display of data plot, I am sure the acquisition is at 25Hz."
He says in the 1st paragraph that he sets theDAQmx timing to 100Hz because that is his maximum expected clock rate. In the 2nd paragraph he says that in his measurement file dt is 0.01 instead of 0.04. This indicates that the dt value is determined by the DAQmx timing rate, not the PFI0 clock rate. I am thinking that he should set the DAQmx timing to match the PFI0 timing, 25Hz.
Maybe this would work.
You're right, I did misread what he said. But, I still have questions about what he said. " I set 100Hz for the rate input of the DAQmx timing VI ". The code shows a rate input of 25 to the timing VI. And nowhere else do I see a setting of 100Hz. I ran his code (used a simulated device) and put an indicator on the to dt's in the clusters. The came up as .04 which is what i would expect. It is hard to comment what is going on in the file since there is nothing being send to the write text file VI.
Message Edited by Ravens Fan on 08-31-2007 12:18 PM

Daqmx read.vi timestamp incorrect problem (storing the timestamp from start task)

Hello,
I have a state machine with 1st state: configure DAQ where i have [daqmx create channel.vi --> daqmx timing sample clock--> DAQmx start trigger--> daqmx start trigger] connected in order
sample clock in continuous mode, 10000 samples to read and sample rate 1000 Hz ,
start trigger has rising edge selected with a dev1/PFI0 from a daq board.
next state of SM is read channels which has daqmx read.vi set to 1d waveform Nchan Nsamp.
and the program first configures and goes to read channels state and is just waiting for the true value on PFI0,
but the time stamp is not updated to current time/ when daqmx read starts instead it is getting the initial t0 from the time when it was in configure DAQ state of my SM in other words it stores the starting time when strart task.vi was run and then updates from then on.
so in effect i am not getting the exact time stamp values while i am running the vi.
i tried to build waveform by inputting the actual current time but the chart doesnot scroll and shows only few values each reading, when i tried to input the t0 from the waveform given out by read daqmx. vi, it then behaves normally..
option #1 from this link says
http://forums.ni.com/ni/board/message?board.id=250&thread.id=47648&view=by_date_ascending&page=2
Try and do exactly what the driver does. This
will require you to do exactly what you are doing in the posted
example. Call the current system time immediately prior to calling the
DAQmx Read and subtract dt * x where x is the number of samples already
acquired. This will require you to know exactly how many samples have
been acquired. This can be found by calling the Total Samples Per
Channel Acquired property immediately prior to the DAQmx Read. This
introduces some points of innaccuracy. For example, you're system time
is already innaccurate to some amount. In addition, it takes some time
between calling system time, calling the total samples acquired, and
calling the DAQmx read. If 2 samples are acquired between calling the
system time and total samples acquired, you could be off by a few
samples. For slower clock rates, you will have more accuracy.
but there are no samples that are acquired until the rising edge, so the number of samples is always zero before the read operation
http://digital.ni.com/public.nsf/allkb/5D42CCB17A70A06686256DBA007C5EEA
this link says that
and the number of samples in my waveform is constantly changing around 20-40, so i cannot really input the current time to build the waveform, thats what i can figure out for now..
can somebody tell me why this is happening or is there any fix around this, how to get the current time into my daqmx read.viso it displays the currect time on my waveform chart
Thanks,

thanks,
im using LV 8.6, daqmx driver 8.9.5.
yes the program u posted get the currect time. but see attached program thats what i have in my program exactly
if you took out the time to using the get waveform components using the waveform from daqmx read. i still have the timestamp as the application start time. plz see attached code 8.2v and FP
the waveform time x axis is not current, it is starting from the application start time.
PS: samples to read = 10,000 and sample rate = 1000
plz help..
Attachments:
daqmx read problemp.png ‏8 KB
daqmx read problem.vi ‏36 KB

Using RTSI on the PCI-7811R FPGA

I have created a FPGA vi that outputs a certain signal that I want to go out a DIO and the RTSI. It goes out the DIO ok. But there seems to be nothing going out the RTSI line. I've added the RTSI resourse to the project, and all I do in the FPGA VI is configure the RTSI as Write, and then simply run a boolean value into it, just like I do with the DIO.
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National Instruments
Applications Engineer

Check RTSI functionality?

Being new to Labview and data acquisition, I've changed a simple RTSI example VI for 2 E-series boards. I cannot see any difference in VI execution if I wire the RTSI triggering to the second device (AI start) or not.How can I be certain that device 2 is really triggered by RTSI0?
Current setup is as follows:
1) AI config board #1
2) Route signal to as
3) AI config board #2
4) AI start board #2, trigger type Digital A, Analog channel&Level:
5) AI start board #1
As mentioned, I see no difference if step 4) gets triggering or not. So, how can I verificy RTSI functionality and confirm signal reception over RTSI?

The example I downloaded did not terminate the RTSI connections by routing the RTSI line used to after VI completion (Another example had both master and slave board waiting for a digital trigger leading to time outs, leading to cross-wired example confusion). Apparently RTSI connections remain open until the boards are reset, feeding the module a trigger on all RTSI lines I had tried to call today (and yesterday...).
Now I can determine RTSI trigger reception per channel by verifying a time out in . If a time out occurs, no trigger has been received.
I'm sure it's written somewhere, but it should be clearer in the RTSI help file that lines must be closed upon VI completion!

RTSI Trigger (DAQmx & C++)

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