11-12-2008 01:44 AM
Hello,
I have a CRIO-9014 with 2 modules: 9401 an 9239.
I feed the DI with a PPS from a GPS. I record the delay between the PPS and the first analog measurement following.
The FPGA clock isn't 40 MHz exactly. The 9239 is a timed module then follow the FPGA clock then I have few microseconds drift every seconds.
By example, one second I will get the first measurement at 10 us and the next second will be at 13 us.
I would like to stack the data .... add together values of few seconds of data and divide by the number of data.
The problem is : I need to shift data depending time of measuremet otherwise the stacking will be wrong
I have tried different options: use the time in a waveform (doesn't work), use a 1M array ( too big, too slow).
Anybody has got an idea?
Mathieu
11-12-2008 04:51 PM
Hi Mathieu,
I am going to cheat and quotethis kb:
"You can use the SMB connector of cRIO-9012/9014/9074 controllers to connect a digital device to the controller. For example, if you connect the pulse-per-second (PPS) output of a GPS device to the SMB connector of a cRIO-9012/9014/9074 , you can use the GPS device to correct for drift of the system clock of the controller. You can also use the SMB connector as a general purpose digital I/O line."
It looks like you want to use the SMB pin for GPS drift correction.