DAQmxCfgSa​mpClkTimin​g NICARD 6031 E PCI and Visual C++ 6.0

Question

To the attention of the support department or someone else wellcome! -):
I am using an NICARD 6031 E PCI. I am also using Visual C++ 6.0.
I declared a variable for an external ANALOG SAMPLE CLOCK. I am supplying
this CLOCK signal to the input PIN /Dev1/PFI7
//, m_sSampClk(_T("ai/SampleClock"))
I am not using this variable now and this is why is commented. Instead, I
just call /Dev1/PFI7 below in the routine.
I am using the following routine to SAMPLE input values based on the
external CLOCK signal entering the /Dev1/PFI7 PIN
nErrorCode = DAQmxCfgSampClkTiming (m_hAnalogTask, //task handle
"/Dev1/PFI7", //Sample Clock from ATMEGA88 (AI SAMP CLK)
50000, //Sampling rate (float64) points per second
DAQmx_Val_Rising, //Acquire samples on rising edges of the
Sample Clock.
DAQmx_Val_FiniteSamps, //Finite mode for buffered hardware
timing acquisition
128); //128 samples per channel
if(nErrorCode!=0) //error encountered
DAQmxGetErrorString(nErrorCode, szErrorMsg, 1024);
AfxMessageBox(szErrorMsg);
Can you please let me know if my routine is correct and I do not need to
declare a variable for the SAMPLE CLOCK because I call it on the routine
directly? I searched examples on your website but I only find LABVIEW and
not Visual C++ examples.
Regards,
Javier Contreras.
Solved!
Go to Solution.

Answer 1

Hi Brad
First of all , thanks very much for your help, it is very much appreciatedI reply below your comments for clarity.
Hi Javier,
To debug a system
with multiple possible points of failure, it really helps to break it
down into smaller, easily verifiable pieces.
For example:
Connect
a known good signal. If you don't know if your position detector works
correctly, then connect something else in its place for now, like a
battery or a function generator. Once you have verified that you can
correctly measure a battery or a signal from a function generator, then
connect your position detector and figure out how to get results that
you expect from it
Ok. I could connect a power supply with a resistance and then I would be injecting a current to the system. In that way I would see on the screen the expected current I am injecting. 
Verify that the signal is connected
correctly using the device test panels in MAX. (Or the DAQ Assistant in
MAX, which allows external clocks and other settings that the device
test panel does not. To get there, right-click "Data Neighborhood",
select "Create New...", select "DAQmx Task", etc.)
Thanks. I already checked whether the connections are properly done in Measurement and Automation Explorer. Never used the DAQ Assistant in Measurement and Automation Explorer but I will try it too. However the connections are correct. Differential with CH0 (PINs 3 and 4 on the 100 pin connector) and CH1 ((PINs 5 and 6 on the 100 pin connector), which is the declared in my code as m_sChannels(_T("Dev1/ai0,Dev1/ai1")). I need differential.
Write your
DAQmx code separately from your UI code. Acquire the data and display
it in a simple, easily verifiable manner (hence OutputDebugString or printf or the debugger). Make sure you get the results you expect.
In the past and now I am using the same UI code to display properly other values from very similar circuits and other circuits, so I believe my UI is working properly for sure.
Write your UI code separately from your DAQmx code. Feed it fake data and make sure it gets displayed correctly.
Again, I am using exactly the same base UI code for other setups and it works fine. 
Once all of the pieces work in isolation, put them together and see if they work together.
I am pretty sure that my UI code works perfectly from other setups.
Looking at your NIWrapper.cpp, here are some specific things you should check:
You
are setting the min/max expected values to -2 and 0. Are those correct?
If you always read -2 or you always read 0, then you should try a wider
range, like -10 and 10. If you're expecting 0-1.8 V, then 0 to 2 would
be better.
Yes, may be I should change it to 0 to 2. However, to be on the safe side just in case my signal polarity is changed, can I use -2 to 2?
You are setting the terminal configuration to
DAQmx_Val_Diff. Make sure you have your signals connected to ACH0/ACH8
and ACH1/ACH9 and that the signals are within +/-10 V of AIGND.
s(Yes the signals are connected properly as I checked in Measurement and Automation Explorer. I declared them as m_sChannels(_T("Dev1/ai0,Dev1/ai1")). Signals within +-10V of AIGND. AIGND is connected to the GND of my circuit as it should. What happened to the UNICODE, etc conversion ISSUE we talked last time? Do I need conversion, etc as you said? I do not have a clue on this conversion issue even after reading your link! -) 
DAQmx
ignores external sample clocks that happen before the task is started.
If you need to send a serial command to start your external device (I
don't know, I didn't read your whole program), it would be better to
start the DAQmx task, send the serial command, and then read from the
DAQmx task, so that you don't miss any external sample clocks.
Yes, this is another issue I was working on. I was trying to send a char, 'r' over the RS232 to synchronise as I did in another code in the past which worked fine.
However, I did not seem to make the MAX232 component do what I wanted. I am using the MAX232a from MAXIM and I attach the datasheet in this email. From my UI code, I first send a char 'r' to an ATMEGA128 microcontroller, and if the ATMEGA128 sees the char 'r' then it starts the sending of data from another component and sends the external CLOCK to the NICARD AIsample pin.
However, the char 'r' from my UI code did not seem to arrive to the ATMEGA128 since it did not start the data acquisition or the clock. I already used this char 'r' approach in the past with the ATMEGA128 too and it worked fine with another type of SMD MAX232. Would it be fine if I measured the voltage values of the MAX232 pins while transmitting the char and then LET you know these values for you to check if the MAX232 works fine?
I also tried another approach to synchronise which is to set from the UI code one pin from the NICARD to HIGH, and then ATMEGA checks if this pin was HIGH and if it was then it transmitted. However, this PIN seemed to stay HIGH and the approach did not work. Of course I would like to synchronise but I have not managed, so I have the ATMEGA128 code sending inside a FOR loop on every iteration.
And the NICARD of course will be receiving sets of 129 CLOCKs on every iteration but spaced with a GAP of 10ms. I wish I could synchronise but it is not working. Can you check the values of the voltages of the MAX232a if I send you the values myself while it is transmitting char 'r'? Just for you to check of course.
You're passing -1 as the timeout for DAQmxWaitUntilTaskDone(). This
will cause DAQmx to wait forever if you don't get enough external
sample clocks, hanging your program.
Yes, I am passing -1. But I am providing enough CLOCK samples (129). I have the CLOCK waveform on a photo I made of the oscilloscope. This hanging of the program was the case, when the ATMEGA128 did not send anything because the PIN remained in the one state HIGH or LOW without changing everytime as it should, in order to inform the ATMEGA128 that it could send data.
I attach the MAX232 component datasheet.
Thanks and best regards.
Javier.
Attachments:
MAX220-MAX249.pdf ‏397 KB