GPIO (General Purpose I/O)

The lines are general purpose because the DAQ assigns them no meaning: what each line is used for is decided by the experiment and recorded in the session's channel map.

Three kinds of line serve three kinds of instrument. Analog inputs acquire a continuous voltage — a photodiode, a treadmill or wheel encoder, a lever position, a lick sensor — sampled and stored as a channel beside the electrode channels. Digital inputs acquire TTL events — a trial start from a behavior controller, a camera frame pulse, a laser or stimulator trigger — timestamped on the same clock as the neural samples, which is what makes an event-aligned analysis exact rather than aligned between two clocks afterwards. Analog and digital outputs drive the other direction: a synchronization pulse to a camera or a second recording system, a reward signal to the training apparatus, or a trigger that a closed-loop protocol issues from what the software sees in the data.

The count of lines is a specification to check against the protocol before ordering. XDAQ ALL-IN-ONE and ONE+ provide 8 analog in, 8 analog out and 32 digital I/O, CORE2 7, 7 and 31; Smartbox provides 2 analog in and 2 digital I/O. GPIO signals appear in Radiens as channels in the same session as the neural data, so a behavioral event and a spike are read from one file. The data acquisition system entry covers how they are synchronized.