I have an application written in ansi C that will create an NI task that will run a continueous collection of several AI lines at a set collection rate (see CollectionRate below). This is a simplified version of the setup of the ai task:
ni_rc = DAQmxCreateTask (
"", // name assigned to the task
&ai_task); // reference to the task created in this function
for (i = 0; i < ai_channels; i++)
{
/* Create an NI AI voltage channel.
*/
if (ai_ptrs[i].chan_num >= 0)
{
char chan_name[MAX_STRLEN]; // NI channel name, e.g. "Dev1/ai2"
//
long chan_num = ai_ptrs[i].chan_num;
sprintf (chan_name, INPUT_CHANNEL_FORMAT, deviceName, chan_num);
ni_rc = DAQmxCreateAIVoltageChan (
ai_task, // task to which to add the channel
chan_name, // names of the physical channels to use
"", // name(s) to assign to the created virtual channel(s)
terminal_config, // differential vs. single-ended
(double) devsupp_ai_channels[chan_num].volts_min, // minimum voltage expected
(double) devsupp_ai_channels[chan_num].volts_max,
(long) DAQmx_Val_Volts, // units in which to generate voltage (unscaled)
""); // name of a custom scale
}
}
ni_rc = DAQmxCfgSampClkTiming (
ai_task, // task reference
"", // clock source terminal (internal clock)
(double)CollectionRate, // sampling rate in hz
(long) DAQmx_Val_Rising, // rising edge of clock signal is active
(long) DAQmx_Val_ContSamps, // continuous sampling
1ULL); // samples per channel to acquire
ni_rc = DAQmxStartTask (ai_task);
Now I need to use an external sample clock. That part will be easy just change the DAQmxCfgSampClkTiming statement to:
ni_rc = DAQmxCfgSampClkTiming (
ai_task, // task reference
CLOCK_SOURCE, // clock source terminal e.g. PFI7 or RTSI2...
MAX_COLECTION_RATE, // maximum sampling rate in hz
(long) DAQmx_Val_Rising, // rising edge of clock signal is active
(long) DAQmx_Val_ContSamps, // continuous sampling
1ULL); // samples per channel to acquire
However I also need to have the external clock GATED by a second external signal. I am sure given the capabilities of the card and the DAQmx software In can be done but how? Do I need to set up a second task with a counter (as a divide by 1). The clock input and gate to the counter will be from a hardware terminal and use the counter output as the CLOCK_SOURCE?
