NMEALog accepts data from up to two instruments natively, or several via a mux and logs data based on settable criteria, such as delta position, delta depth, delta time. Data is logged onto an SD-card and one card can hold several months worth of data.
The project image shows an existing chart with added depth data (darker blue)
Two input channels, optically isolated
On-board capacitor backup that flushes and closes files on power loss