Petrel Firmware V27

Petrel Firmware V27

NOTE: You must have Shearwater Desktop 2.3.8+ to perform this update.

Download the complete change log in the Petrel Firmware V27 Release Notes
Download the firmware here: Petrel Firmware V27

Firmware Update Instructions

Note: Updating the firmware will reset the decompression tissue loading.

  1. Ensure that you have Shearwater Desktop 2.3.8+
  2. Save the above .zip to your desktop or laptop computer.
  3. Extract the .swfw file from the zip and save it to your desktop
  4. In Shearwater Desktop, go to Dive Computer > Update Firmware... and select the firmware .swfw file.
  5. On your Petrel, navigate to Dive Log > Upload Log and wait for the 3 minute countdown timer to begin.
  6. Go back to Shearwater Desktop and click the Start button.

NOTE: Hardware Versions for Petrel 1 and Petrel 2


Petrel 2 Digital Compass
Petrel firmware v27 is the first version to support the new hardware features of the Petrel 2, which are:


  • Tilt compensated digital compass.
  • Smart Ready Bluetooth (to add support for iOS devices).

A single firmware file and version number will be used for both the Petrel 1 and Petrel 2. All new features will apply to both models, except those related to the hardware differences listed above.

Listing of changes in Petrel Firmware v27

Petrel 2 Only:

  • NEW FEATURE: Tilt compensated digital compass. Accessed by pressing the right button once.



Calibrate the compass, using the “System Setup > Compass” menu, before first use.

Instructions in the manual or at:

Instructional Videos

NEW FEATURE: Bluetooth Smart Ready for Apple iOS device support. The Bluetooth Smart Ready module supports both Bluetooth Classic (v2.1) standard and the new low energy Bluetooth Smart (v4.0) standard.

All Models:


  • temp graph dive log

    Temperature Graph in the Dive Log

    NEW FEATURE: A plot of the dive temperature is now shown in the dive log view. Also shows minimum, maximum, and average temperature for the dive. Accessed after the dive log graph.

  • dive info

    Additional dive information can now be viewed in the dive log

    NEW FEATURE: Additional information can now be viewed in the dive log view. Accessed after the temperature graph (see above). Includes:

    • Mode (OC Tec, OC Rec, OC/CC, Gauge, etc)
    • Surface Interval
    • Surface pressure in millibar
    • Deco model and conservatism
    • Start CNS %
    • End CNS %

  • CHANGE: When surface pressure is less than 960 millibar, now forces the use of auto altitude setting (i.e. cannot use the SeaLvl setting). This does not change the saved setting.
  • The dive planner now inserts ascent legs in the results table to perform gas switches during the initial ascent to the first deco stop. The decompression calculations always included these switches, but the planner results were only showing a single ascent to the first deco stop using the bottom gas. This change results in more accurate gas usage results for some dives.

EXT Model:

  • External PPO2 monitoring is now supported for 2 sensors (previously only allowed 1 or 3 sensors). Access the 2 sensor mode by performing a PPO2 calibration with only sensors #1 and #2 connected (single sensor mode accessed by calibrating with only sensor #2 connected). When using the 2 sensor mode, a configurable value may be displayed on the right side of the screen.

Two sensors can now be used in the external PPO2 monitoring mode

(not available on controller models)
A configurable value (maximum depth in the above image) can optionally be displayed

The voting works as follows in 2 sensor mode:

Voting Passed

  • If sensors within 20%, voting passes and the average PPO2 of the two sensors is used for decompression and CNS calculations.

Voting Failed

  • If the two sensors differ by more than 20%, voting has failed.
  • Failed sensors are shown in yellow (unless below 0.4 or above 1.6, then they will be shown in red).
  • PPO2 display will alternate with the message “VOTING FAILED”.
  • The lower PPO2 value will be used for decompression calculations.
  • The higher PPO2 value will be used for CNS calculations.