Best way to acquire data from both serial port and D/A board in real time?

[elsafanny]

In my experiment, I have 2 kinds of data: analog and digital. Now, I have to write a programme to acquire both data not only in real time but also in sychronicity. My colleague tried to write a program for this purpose. However, the digital part was failed. For example, the data length found from "data buffer" is correct in the first 10 seconds; however, the format became wrong later.

Is it one program involved two different data acquisition methods? 

[Conseils]

Hi,

You need to figure out when the serial port sample occured by some technique and then obtain the equivalent sample from the aquisition board, probably from a circular buffer. If you know the sample rate (pretty implicit really) you can 'cherry pick' the appropriate measurement from the buffer to be synchronus with the serial port measurement.