two cyton boards: synchronize sample clock, offset time
sherrywang
Calgary
Hi! Our lab is planning to use LSL for data recording. If we use two cyton boards with their own usb dongle or wifi shield, the maximum time offset will be 8ms(since each of them has +/-4ms), is that correct? Is there any efficient way to measure the offset? And how can we synchronize the sample clock of the two boards? Thanks!
Comments
Sherry, hi.
See this related thread,
http://openbci.com/forum/index.php?p=/discussion/1850/synchronizing-two-cyton-daisy-boards-in-order-to-get-32-channels
Is your application measuring a single subject, or 2 subjects? The sample clocks on the two boards cannot by synced, due to hardware and firmware restrictions. I do know that LSL has some ability to relate the timing of two LSL streams by the use of NTP Network Time Protocol logic in the LSL libraries. But not the same as the precise sample alignment that happens with the same sample clock -- as with the mainboard and Daisy. Nor do I think you could count on the LSL offset time staying exactly the same over the same or even different runs.
If this is two subjects and you want an approximate synchronization, you could possibly use one of the GPIO output pins on one Cyton, connected over to the Aux channel (there are 3 of them) on the other Cyton. This is the same idea used for External Trigger. You could mod the firmware on the generating Cyton, to toggle a square wave off/on, say once per second.
Regards,
William