Why is my board triggering on the wrong edge?

Question

I am using 3 PCI-6110 S Series boards to acquire several channels of analogue data. I have the same trigger signal connected to pin PFI0 of all of these boards which I wish to use to start my acquisition. Although I have configured this trigger to start acquiring on the falling edge, I see that it is sometimes starting on the rising edge - although the majority of the time it does start on the falling edge. It would also appear that when the first card triggers on the 'wrong' edge, the other 2 cards trigger on the correct edge despite the same signal being connected to all. I cannot tell if the other 2 cards ever trigger on the wrong edge when the first one doesn't.
Does anyone have any suggestions as to why this might happen? Optimally I would like the acquisition to start on the correct edge only but if all my cards would at least start on the same edge then I could get round that. To this means I am looking at perhaps using a RTSI cable between the cards. Should this do the trick?
The configuration I am using (for all 3 cards) is as follows:
siStatus = DAQ_Config(Device, 1, 0);
//although I believe that DAQ_Config() above actually calls this next line I have it in anyway:
siStatus = Select_Signal(Device, ND_IN_START_TRIGGER, ND_PFI_0, ND_HIGH_TO_LOW);
siStatus =  AI_Change_Parameter(Device, ND_PFI_0, ND_AI_COUPLING, ND_DC);
siStatus = SCAN_Setup(Device, m_siNumberOfChannels, m_pasiChannels, m_pasiGains);
siStatus = SCAN_Start(Device,...);
One thing I was uncertain about was whether to use 'ND_IN_START_TRIGGER' or 'ND_IN_SCAN_START' in 'Select_Signal()' as I am unsure of the difference. But as my card didn't seem to trigger at all when I used 'ND_IN_SCAN_START' I removed it! I have also tried adding the line:
siStatus = Configure_HW_Analog_Trigger(Device, ND_ON, liLowLevel, liHighLevel, ND_HIGH_HYSTERESIS, ND_PFI_0);
where I had liLowLevel = 138 and liHighLevel = 154 to represent 0.8V and 2V respectively but my card did not at all. (It looked to me like perhaps there is an error in the NIDAQ help for Configure_HW_Analog_Trigger() in the calculation of these levels for a 12 bit bipolar device which uses:
level = (voltage/5 +1) * 128
so I used
level = (voltage/10 +1) * 128
- is this correct?)
I used this in case my trigger signal had some noise spikes on the rising edge that were being mistaken for falling edges although this looks unlikely.
I am desperate to get this fixed as am on a tight schedule so would appreciate any suggestions.

Answer 1

a shame that Apple Support Communities didnt answer to you yet.
I guess you CANT make a 16:9 ratio picture just because the software does not make you do so.