The present invention relates to a handheld upgrade tool comprising nonvolatile memory (320), an information element (330), an I/O port connector (340), a sensor port connector (350) individually attachable to a sensor port (210) of a patient monitor in lieu of a sensor (30), the sensor port electrically connected to a processor board (200) comprising a plurality of firmware instructions executable by the processor board to calculate a plurality of physiological parameters in response to a sensor signal received from the sensor a tool digital signal processor (DSP) (310) configured to authenticate the processor board, wherein to authenticate the processor board the tool DSP is configured to verify that a valid processor board is connected to the sensor port by performing a successful encrypted handshake with the processor board, wherein an encrypted handshake is successful if the upgrade tool recognizes the processor board and the processor board recognizes the upgrade tool, and determine that a board type of the processor board matches an upgrade tool type of the handheld upgrade tool, and based on authentication of the processor board, make an additional parameter available for output by the patient monitor, wherein making the additional parameter available for output by the patient monitor enables the processor board to calculate at least one additional physiological parameter in response to the sensor signal received from the sensor.
