data flow synchronization

[acoustic50]

i am working on a senior thesis project involving sound localization and am running into a problem involving the syncrhonization of my data inputs. basically i have four receivers providing digital inputs through the daq. if a signal is hi i need to obtain the time at which it went hi and pass it on. after obtaining hi signals from 3 out of the 4 receivers within an interval of 15 ms i then need to perform a calculation to find the position (using a matlab script node). as of now i am able to determine times/hi signal arrivals/presence of 3 hi signals. the problem that i am having is that for a transmitter pulse of 1 ms in duration (every 70 ms) i obtain the same times of arrival for the 3 receivers that go hi. (i.e. if lines 1,2, and 4 go hi i get 1.652 sec for all of them). this is not accurate as the transmitter is not located in the center of the sensor distribution and the maximum time of flight is approx 10 ms. upon examining the program with the highlight execution function i noticed that the different portions of the data are executing at random times (i.e. the process is not sequential.) thus, the local variables containing the times of arrival are not necessarily stored directly after a hi signal is recorded for a particular input line.

i attempted to use a sequence structure (frame 0: initialize start time, frame 1: take data/present time from line 1 (if lo, set the time of arrival to 0, if true, set the time of arrival as the "preseent time", frame 2: same w/ line 2, fr 3: same w/ line 3, fr. 4: same w/ line 4, etc...) this doesn't work well though (3 sensors are never interpreted as simultaneously hi).

any ideas on how to fix this problem would be greatly appreciated!!!! thanks!

[vicky]

Hi,
Could you post your code or some sample code so that we can figure out the best way out.
cheers
vicky
Labview7.00