The Flexi 1 incorporates a single serial port, which can be used to communicate with external devices or sensors. It supports RS232 and TTL signal levels. This can be selected by physical jumpers on the Flexi 1 PCB; Set both towards the dot for RS232 level, or away from the dot for TTL level. Both must be set in the same position. Current firmware does not use the serial port, but please contact Digital Matter regarding adding support for existing devices or sensors.