Detecting Falling Edges of Pulses

Learn how the Time Tagger distinguishes rising and falling edges of a pulse and how each is represented in your data.

On the software level, the rising and falling edges are independent channels. In the Graphical User Interface, Time Tagger Lab, the rising and falling edges are marked explicitly with a pictogram. In the software libraries, the number of a falling edge channel is a negative number of the physical input. For example, the rising and falling edges of the physical input 2 correspond to the software channels 2 and -2, respectively. You can also use the method getInvertedChannel() to find the inverted channel number for your specific hardware revision.

Note: Time Taggers delivered before mid-2018 used a legacy 0-based channel numbering scheme, where rising and falling edges were assigned separate, non-negative channel numbers rather than positive/negative pairs. This legacy scheme was supported in software up to v2.21.2. Starting with v2.22.0, only the current 1-based scheme described above is supported, with rising edges numbered 1 to N and falling edges -1 to -N. If you are upgrading to v2.22.0 or later and have code written for older hardware, you may need to update your channel numbering accordingly. See the documentation for the full legacy-to-current channel mapping table.