Abstract: Application of the modem VLSI digital technology to the area of portable sonar equipment, like depth sounders, fish finders, short-range sonars etc., provide automatic acquisition and recording of acoustic data, along with communication with various marine equipment, like chart plotter, GPS, or even host computer, using NMEA OJ83 protocol. The paper presents one such application, which constitutes the design of miniaturized microcontroller driven digital echosounder, and in particular (he bathymetric data processing employed in this design. The dedicated software for such a system consists of two parts: one hard-coded in the microcontroller EEPROM memory and the other running on attached equipment. The first one uses unique features of the microcontroller, which allows real-time compression of echo data, implementation of bottom tracking algorithms and communication with host computer, while the latter in general is used for presentation of echo signals and displaying of various echogram graphics along with associate reports.