Ben J-
Thanks for the reply, I *think* I made some progress this afternoon - the cards are getting triggered and data is getting collected now at least.
I didn't select a clock source for ch1 specifically in the initial code - my very thin understanding of DAQmx leads me to believe that specifying that channel as an empty string causes it to use its internal clock. I could be wrong, I'm very new to DAQmx. Anyway, I re-wrote the code to just include two Tasks instead of representing each DAQ board with its own object, and gave specific timing info to each Task just to be certain of what they were doing.
The code that worked in terms of collecting data is listed below. The one thing that I'm not confident of is the RTSI routing. It seems I can specify signals from the Dev1 card as inputs for the Dev2 card which suggests that these signals are routed automatically, but I'd love to know how to verify that this is true. Our measurement is very sensitive to clock skew between the two cards so checking that the RTSI signals are properly routed would put a lot of minds at ease.
Best regards,
Eric
void IDAQmxCards.ColectData()
{
// set up channel 1
try
{
task1 = new Task("Task1");
// Channel definition
aiChannel1 = task1.AIChannels.CreateVoltageChannel(
"Dev1/ai0",
"Dev1_ai0",
AITerminalConfiguration.Differential,
ch1MinVoltage,
ch1MaxVoltage,
AIVoltageUnits.Volts
);
// Sample Clock
task1.Timing.ConfigureSampleClock(
"OnboardClock",
sampleRate,
SampleClockActiveEdge.Falling,
SampleQuantityMode.FiniteSamples,
samples
);
task1.Control(TaskAction.Verify);
task1.Done += new TaskDoneEventHandler(Task1_Callback);
}
catch (DaqException dEx)
{
MessageBox.Show(dEx.Message, "NI-6250 Ch1 Error");
task1.Stop();
task1.Dispose();
}
// set up channel 2
try
{
task2 = new Task("Task2");
// Channel definiton
aiChannel2 = task2.AIChannels.CreateVoltageChannel(
"Dev2/ai0",
"Dev2_ai0",
AITerminalConfiguration.Differential,
ch2MinVoltage,
ch2MaxVoltage,
AIVoltageUnits.Volts
);
// Sample Clock -> use Dev1 clock
task2.Timing.ConfigureSampleClock(
"/Dev1/ai/SampleClock",
sampleRate,
SampleClockActiveEdge.Falling,
SampleQuantityMode.FiniteSamples,
samples
);
// Trigger off Dev1 StartTrigger
task2.Triggers.StartTrigger.ConfigureDigitalEdgeTrigger(
"/Dev1/ai/StartTrigger",
DigitalEdgeStartTriggerEdge.Falling
);
task2.Control(TaskAction.Verify);
task2.Done += new TaskDoneEventHandler(Task2_Callback);
}
catch (DaqException dEx)
{
MessageBox.Show(dEx.Message, "NI-6250 Ch2 Error");
task2.Stop();
task2.Dispose();
}
// Start tasks, begin task2 first since it will wait for signals from task1
task2.Start();
task1.Start();
}
// Callbacks
void Task1_Callback(object sender, TaskDoneEventArgs e)
{
// read
AnalogSingleChannelReader reader = new AnalogSingleChannelReader(task1.Stream);
ch1Data = reader.ReadMultiSample(samples);
// stop task and release hardware
task1.Stop();
task1.Dispose();
}
void Task2_Callback(object sender, TaskDoneEventArgs e)
{
// read
AnalogSingleChannelReader reader = new AnalogSingleChannelReader(task2.Stream);
ch2Data = reader.ReadMultiSample(samples);
// stop task and release hardware
task2.Stop();
task2.Dispose();
}
