Sentinel Automatic Trigger System (SATS-MINI) Quick Start Guide and Resources

Use this resource to get started with the SATS-MINI

SATS-MINI Product Guide PDF

SATS-MINI Users and Programming Guide PDF

Purchase the SATS-MINI

Software Downloads - Current latest version is 1.1.2 (Important Bug Fix for 1.1.1)

Download Version 1.1.2 - Current Production Release

IMPORTANT - This release fixes some critical bugs reported by the field and it is essential to install this update.  This fix only affects the SATS-MINI firmware, the Shooty Chute UI functionality is the same as V1.1.1.  If you already have V1.1.1 of Shooty Chute installed you do not need to reinstall the V1.1.2 of the Windows UI. There are no core feature changes between versions 1.1.1 and 1.1.2.

Bug Fixes:

Logging Bug

  • The shutting down the SATS-MINI while in Armed, and the SATS-MINI is logging, there was a bug related to closing out the current log properly.  In some cases log data could still be written to the flash memory after the shutdown is triggered and it could write fragments of data and cause problems with the next power-up.
  • Not properly closing out the log can then lead to the next log number jumping to some random log number.
  • In some cases it can cause the SATS-MINI to not properly export all logs so some may be missing.

IMU Initialization

  • In burn-in cycle testing we would occationally see an issue where the IMU is not initialized correctly despite all the IMU self tests sucsessfully passing.  This would cause the accelerometer data to read zero for the X / Y / Z axis and when armed could lead to a false trigger.  The bug fix impliments a more rigorous set of secondary testing that checks the IMU accelerometer and that the magnitude of X / Y / Z is between 0.9G and 1.1G of acceleration.  If an error is detected the IMU is reinitialized again until the secondary testing passes.  If there is a cronic inability to get the IMU to initialize the SATS-MINI will enter the ERROR status and be non-operational.

IMPORTANT NOTE ABOUT BEST PRACTIVES - The SATS-MINI includes features that allow it to automatically turn on in the armed state and be ready to go when external power is applied via CH3, or CH4.  When power is removed the SATS-MINI can be programmed to automatically turn off after a period of time.  But even while the SATS-MINI has these features it is not set and forget! It is STRONGLY recommended that the pilot always check the SATS-MINI for proper operation before takeoff. If an unrecoverable error is detected the SATS-MINI will hold in the ERROR state (pulsing purple light) and will not monitor the flight.  In this case simply power cycling the SATS-MINI will clear this.  In testing over 1000's of power cycles the odds of this accuring are very small, however it is still best to always have a pre-flight check that the SATS-MINI is ready to go.

Upgrading: See "Install Shooty Chute Windows UI" and "Updating the Firmware" below.

Version is 1.1.1

Download Version 1.1.1 - First Production Release

Version 1.1.1 is considered our first non-beta production release and has many improvements over previous versions. Included are a number of new features both for the SATS-MINI, and the Shooty Chute UI.  There are also some bug fixes. We urge all SATS-MINI users on 1.0.XX beta versions to upgrade.  New in this release are:

Support for SATS-MINI V2.1 Hardware! The new version of the SATS-MINI adds a real time clock (RTC) so logging can be time-stamped when various log events happen, like log start, trigger event, power events, and shutdown events.  The RTC draws just 40 nano-amps and is very accurate with a temperature and voltage corrected time base.  Once set the RTC can run indefinitely as long as the Lipo battery stays connected and has even the most minimal charge even below 3.0V.  The V1.1.1 Shooty Chute UI includes a button that sets the RTC time to your PC time.  

SATS-MINI Operational Features:

  • Configurable automatic shutdown after external power removal.  In V1.0.29 the turn off time was set for 2 minutes.  Now this is configurable for between 15 seconds to 10 minutes.
  • Automatic power-up in Safety / Armed. This feature makes sure that when the SATS-MINI is powered up is is always ready to fly.  This removes the possibility of power-up and then the user forgets to arm the SATS-MINI.  This feature should be used in conjunction with the Safety features.
  • Comprehensive error reporting.  There is more error detection now at powerup to make sure all the sensors are working and the IMU has no errors.  If there is an error the status LED will flash Purple at startup and the SATS-MINI can not be armed.  Connecting to the new Shooty Chute UI the errors are displayed on the dashboard.
  • Variable Log Rate.  You can now configure the detail flight logging rate for the SATS-MINI and to 5 Hz, 10 Hz (default), of 20 Hz.  Below is the log capacity at each of these:
    • 5 Hz logging capacity: 12hr 25min
    • 10 Hz logging capacity: 6hr 49mi
    • 20 Hz logging capacity: 3hr 6mi - This is useful when doing parachute system testing, or other testing, and you want the best resolution possible.

SATS-MINI Trigger Features:

  • Primary Axis Tolerance maximum is now 90 degrees.  This can be uses in conjunction with Tumble rotation of 90 degrees providing a fast trigger if the drone tips just 90 degrees.  This may also be usefull for VTOL, or Fixed Wing where a complete rotation is unlikely.
  • Altimeter Based Fall.  This trigger watches for a given descent distance occurring within a given time.  The default is a fall of 12 meters of fall happening is 1 second or less.  This triggers guards againt what can be described as a slow-motion crash where the done is not in freefall, or completely out of control, but instead descending at an unsafe rate.  For example, if the Lipo power on the drone is nearing complete discharge.
  • External Voltage Monitor.  This allows you to connect your drones main Lipo battery voltage to the expansion port pin 8.  The Shooty Chute UI lets you configure your minimum acceptable battery voltage.  When the feature is enabled the SATS-MINI will trigger the parachute if the external voltage monitor falls below the threshold for 0.5 seconds. The maximum voltage that can be monitored is 33.2 volts allowing you to monitor up to a 6S battery.

Bug Fixes:

  • Sometimes at startup the IMU could come up in an error state.  We discovered that one of the Magnetometer calibration values could sometimes be out of bounds causing this. Code was added to make sure this overrange IMU calibration value is limited when needed.  Even with this the IMU self-calibrates quickly and resumes normal operation in just a few seconds.
  • Error detection for the IMU was not properly watching for all the initialization errors in some cases.
  • Fixed a corner case in the rotation detection algorythem when using small Tumbling angles like 90 degrees, along with large Yaw rotation angles like 540 degrees. In certain combinations of movement this can cause problems when the Primary Axis Tolerance is exceeded causing the parachute ejection. We have no reports any customers had this issue.  We recognized the issue in our own testing.
  • Better detection when using mis-matched version of the SATS-MINI firmware and the Shooty Chute UI to alert the user of the problem. You should always be using the same version of all the software.

Upgrading: See "Install Shooty Chute Windows UI" and "Updating the Firmware" below.

Past Versions

Download Version 1.0.29 (Beta 3)

IMPORTANT UPGRADE INFORMATION FOR V1.0.29 - V1.0.29 has an important change for users of the Pixhawk with the PX4 software base.  When the Pixhawk powers up all the outputs produce a single 2000us PWM pulse regardless of the settings.  If you're using a channel from the Pixhawk into the SATS for an external parachute trigger input to the SATS. This can cause the SATS to eject the parachute.  Version 1.0.29 now required 3 PWM pulses in a row that satisfy the external PWM trigger input in order to eject the parachute. V1.0.29 has no configuration changes from V1.0.28 and will upgrade seamlessly.

If you still have V1.0.27 we strongly recommend that all these users upgrade to this latest version.  While 1.0.27 does not have any problems that hinder critical operation there are some important bug fixes regarding some UI interactions with the SATS.  Also features regarding secondary channel types have some minor bug fixes.

For people upgrading from V1.0.27 follow the notes below for installing the UF2 firmware file into the SATS-MINI.  This version must be used with the version 1.0.30 Shooty Chutes Windows UI so be sure to install that. The installer will seamlessly upgrade older versions. Again see the notes below regarding upgrading the SATS-MINI and migrating your settings to the new version.

After upgrading and restarting the SATS-MINI will power-up in the Error state and will pulse purple.  With the new Windows UI go to Tools - Factory Reset to update the SATS-MINI EEProm and Flash memory. After restarting the SATS-MINI should power-up in Idle quickly.  Sometimes after factory reset the SATS may not immediately restart. In that case force the SATS-MINI off using a paper clip. Then turning on the SATS-MINI should be fine.

Download Version 1.0.28 (Beta 2)

V1.0.28 has some important bug fixes regarding some UI interactions with the SATS.  Also features regarding secondary channel types have some minor bug fixes.

New in V1.0.28 is a feature (optional) that allows the SATS to auto-turnoff after external power is removed.  This coupled with the auto-on when power is applied allow you to connect your autopilot +5V power to Channel 3 or 4 power pin (pin 2).  When the autopilot supplies 5V power the SATS will automatically turn on. When the auto-pilot turns off the SATS will then wait 2 minutes and turn itself off.  With this feature enabled you don't need to manage the SATS_MINI power, it will automatically turn on and off with your drone power. If there is a complete loss of power to your autopilot this likely means the drone is going to lose control and crash. The SATS-MINI will detect the drone falling and trigger the parachute before the unit turns off.

Download Version 1.0.27 (Beta 1)


We always ship the SATS-MINI pre-loaded with the latest software available and with the default configuration.  If you ordered the SATS-MINI as part of a bundled product, like the Inspire 2 or Mavic 2 parachute the SATS-MINI comes pre-set with the Z axis orientation set. Also, the channels come pre-configured for proper operation.  Before flight do charge the SATS-MINI via the USB port. We DO recommend thorough ground testing before flight to validate operation. See the instructions below for basic operation. If you have any questions about the device, please contact us!

Get Started Here

Here we give you the most important information you need to get up and going fast. Much of this information here is also covered in the SATS-MINI Product Guide and the SATS-MINI Users and Programming Guide so be sure to refer to these for more detailed information.

The Sentinel Automatic Trigger System (SATS-MIN) has many complex programmable features that can be setup using the Shooty Chute Windows UI program. Once the configuration is uploaded the only thing you need to do to fly and protect your drone is to turn on the SATS-MINI. Also before you fly be sure the SATS-MINI is in the operational Safety / Armed state so the parachute can trigger. After flying, disarm the SATS-MINI and power down. Later you can download your flight log to your PC using the Shooty Chute app. If you parachute is needed the flight log becomes an essential part of diagnosing what the failure is.

Preloaded Default Configuration

The SATS-MINI comes preloaded with a default configuration that will work for most drone applications. In this configuration the channels are programmed as:

Safety Altitude - This is set to 0 so the altitude-based safety is not active.  After testing you may want to set this to typically 10 meters so the SATS stays in safety until 10 meters above ground level (AGL). Above 10 meters the SATS-MINI will auto-arm.  Download the flight log file to verify proper operation.

External Power Auto-Shutdown - It is generally cleared.  For some parachute systems this will be enabled.  For example, the Inspire 1 or Inspire 2, these bundles have external battery power supplied by the Skycat V3 Trigger (connected to Channel 3).  The SATS-MINI will automatically turn on and off with the application and removal of the external power. If you use the SATS-MINI with the Pixhawk you may also want to use this feature.

Channel 1 - Trigger, Trigger output, PWM, servo sweep 45 degrees to 135 degrees, no delay, 5V Power Out - Use this channel for the Harrier or other launcher that needs a servo PWM signal

Channel 2 - Trigger Delayed, Trigger Output, PWM, servo sweep 45 degrees to 135 degrees, 500ms delay, 5V Power Out - Use this channel for your PWM output if you want to delay the parachute trigger. In that case you would use Channel 1 for Flight Termination, then Channel 2 to eject the parachute 500ms later.

Channel 3 - Skycat V3 Trigger, Trigger Output, PWM, servo sweep 45 degrees to 135 degrees, no delay, 5V Power In - This channel is preconfigured for the Skycat V3 trigger. Channel 3 can accept power from the V3 Trigger. And at the same time this channel will provide the PWM output to launch the parachute.

Channel 4 - Nano RX, Trigger Input, PWM, Trigger PWM 2000us, 10% Tolerance, 5V Power In - The optional TBS Nano receiver, if installed, will use this channel in order to provide an PWM trigger signal so you can remote eject the parachute from the Skycat rescue radio. If the Nano is not installed then you can use Channel 4 for any other virtual IO feature.

Failure Detection Settings used to trigger the parachute are defaulted to:

  • Tumbling (Non-Primary Axis) - 360 degrees roll in under 2 seconds

  • Yaw (Primary Axis) - 540 degrees rotation in under 2 seconds

  • Free Fall - Accelerometer fused X/Y/Z magnitude threshold <= 0.3G for >= 0.5 seconds

These settings will work for most all drones like the Mavic 2, Phantom 4, and other DJI drones. The settings will not result in false triggers for normal flying conditions.

To change the settings, use the Shooty Chute Windows UI to edit the configuration. See the SATS-MINI Users and Programing Guide for details how to use the program.

SATS-MINI Basic Operation

Below is a rendering of the SATS-MINI case and the various features.

To turn on the SATS-MINI press and hold the System Mode button for 2 seconds. Once the indicator lights come on release. The SATS-MINI will come up in the same System State it was in when powered down. The mode light may temporarily show solid Purple if there is a startup process that needs to happen before going to the operational state. In rare cases it can remain solid Purple for several minutes so just wait.

To Turn Off the SATS-MINI quickly press and release the System Mode button. The SATS-MINI will beep twice, high then low. After that press and hold for two seconds. The SATS-MINI will do a Triad of beeps and turn off.

To change SATS-MINI operational states press and hold the System Mode button for 1 second and it will transition between operational states. The beeper will also sound.

Install Shooty Chute Windows UI

1 - Download the SATS-MINI Windows UI software from our website (link on this page).

2 - Double click on the ShootyChutes.msi file and follow the steps. Windows will complain that the publisher is unknown. Click the links to force Windows to install the software. You will need to agree to the End User License Agreement.


Using the Shooty Chute UI

1 - First plug in the SATS-MINI USB port to your computer first so the COM port is created. This will also turn on the SATS-MINI.

2 - Start Shooty Chute.

3 - The serial port of the SATS-MINI should be listed. Click Connect. The box next to Connect should turn Green.

4 - Physically moving the SATS-MINI should cause the 3D box rendering to track the movements.


Control Panel

NOTE: If the SATS-MINI does not have a valid configuration then the Status LED will pulse PURPLE. In this case you need to send a default configuration to the SATS-MINI and restart. To do this use Tools - Send Default Configuration. After restart the status LED will flash Green and the UI Drone will track the movement of the SATS-MINI. WHen upgrading the SATS-MINI firmware we recommend that you do “Tools - Reset to Factory Defaults”. The software release will indicate when that is needed.


Updating the Firmware

The SATS-MINI is always shipped with the latest firmware software. When new versions are available the firmware installs for the SATS-MINI are provided as a self installing UF2 file format.

Before you start: Before upgrading save your current SATS-MINI setup to your hard drive.  Also download your log file if you want to save it. After you upgrade you can reload your configuration saving you setup time.  Always test your configuration thoroughly before flight.

In order to install:

  1. Power-up the SATS-MINI and connect the USB cable. You should hear the beep that the USB port is recognized. 

  2. Before you start, make sure the SATS-MINI is in the Idle state, the green light should be flashing which is Idle.

  3. To load the firmware, first you need to put the SATS-MINI into the bootloader mode. To do this use a paper clip or other small tool and press the reset button through the clear bezel twice within 1 second or less. There is an access hole in the SATS-MINI case to reach the Reset button. This will put the SATS-MINI into the Bootloader mode and a Drive letter will show up in your Windows File Explorer that says FEATHERBOOT. The status LED will also pulse red. 

  4. Open the release folder on your PC. Drag the file ATS.UF2 file into the FEATHERBOOT folder and you should see the red light flicker and the SATS-MINI will restart. 

  5. The green idle light will start to flash and the SATS-MINI with be in Idle.

  6. Connect the Shooty Chute UI and do the Factory Reset in the Tools section.



To Configure the SATS-MINI


1 - After connecting click Tools - Device Setup. The current setup for the SATS-MINI will be pulled into the UI. 


2 - At this time you can reload your saved setups.


3 - You can now do any other configuration items needed at this time. After making a change be sure to upload to the SATS-MINI which will automatically restart the unit.


General Settings

Advanced Settings

IMPORTANT!: Be sure to ground test any updates you make. It’s less expensive to discover setup issues on the ground rather than in flight!

SATS-MINI Primary Axis Calibration

In order to optimize the SATS-MINI detection algorithm you need to tell the system which way is up. The calibration procedure allows you to mount the SATS-MINI on your drone in any imaginable orientation and it will work the same. Follow these steps:

  1. Mount the SATS-MINI on your drone. Any orientation is OK.

  2. Turn on the SATS-MINI and first initialize the IMU magnetometer by rotating the SATS-MINI (or rotate your drone) a few rotations around all three axes. The internal Co-processor will then learn the position of magnetic north. If you have a large drone it may be easier to detach the SATS-MINI and rotate it on it’s own, then reattach.

  3. This next step is optional and is not required for proper SATS-MINI operation. In order to have the SATS-MINI exactly track your drone movement so the Shooty Chute animated UI drone matches the physical drone movement you will want to orient your drone to face magnetic North. If you have a cell phone compass, or a tool like GPS Essentials it can tell you which way to point your drone. 

  4. Next put your drone in a level position (optionally facing magnetic north) so we can capture the physical SATS-MINI orientation. In the UI go to Tools - Device Setup. Click Acquire in order to capture the raw IMU orientation. You will see angle values populate the X / Y / Z fields. Clicking acquire again should result in consistent values.

  5. Upload that to the SATS-MINI and restart the SATS-MINI.

  6. Reconnect the UI and the SATS-MINI and the UI drone should appear level and the drone arrow will face away from you. If you did step #3 your movement of the drone tilting will be exactly matched by the UI Drone. Also, it’s key that the IMU is internally calibrated (step 2). If it does not face away from you the IMU magnetometer may not have been completely settled when you acquired the position. Repeat the calibration process if needed. In any case the Z axis will be very close to optimal for the detection algorithm to work properly after calibration.


If you have a parachute deployment the log file is a critical tool to determine the exact cause of the drone failure.  So managing the log and making sure you can capture flight information is extremely valuable.

When the SATS-MINI is in safety or armed trigger events, flight data and other events like low power are logged to the onboard Flash memory. The Flash memory will hold approximately 6 hours of detailed log data when running at 10 Hz. Once at 30 minutes or less log space available only critical events are logged. To dump the log to your hard drive, do the following:

1 - Connect the Shooty Chute UI to your SATS-MINI.  Then go to Tools - Dump Log.

2 - Enter the file name to save to. The dump is in CSV format and can be easily viewed in Excel.

3 - Click Save. The message box will tell you once the dump is completed.

After dumping logs are not deleted. Instead new logs are appended and a new log number assigned. You can erase the log using Tools - Erase Log.

Using the SATS-MINI with Pixhawk Based Systems

The Pixhawk hardware platform can work well with the SATS-MINI depending on the software stack used. The key feature needed is the ability to stop the rotors when the parachute is ejected by the SATS-MINI. Also the SATS-MINI can be driven by the Parachute Channels output of the Pixhawk to provide external trigger of the SATS-MINI to eject the parachute. The defaule SATS-MINI configuration has CH4 setup for external trigger 2000us, 20% tolerance.  The the Pixhawn parachute output to this PWM pulse width.  Also the Pixhawk 5V power pin on the Parachute output channel will also feed power to the SATS-MINI to keep the Lipo battery charged.

PX4 Software Stack - The latest version of the PX4 now has support for Flight Termination built in.  The feature in not yet merged into an official branch (V1.10 is the latest, but does not have support), but is in Master.  Here is the documentation on how to setup Flight Termnination: - General article about flight termination done by the PX4 firmware - External ATS Integration to support Flight Termninatioin. This lets the SATS-MINI stop the rotors. Connect one of the PWM parachute out channels to Aux5 or Main5. Termination happes when the SATS-MINI assets a 2000us signal (135 degrees).

ArduPilot Software Stack - This software stack has parachute support already, but it does not have external Flight Termination allowing a tight integration with an external ATS like the SATS-MINI.  We have submitted an enhancement request to have external Flight Terminationi supported but there has not been any effory yet to comnplete this.  Here is the request:

If this seems valuable please advocate for this to the ArduPilot development community so we can get this implimented.

Testing and Verification

After setting up your SATS-MINI be sure to test and verify all operations.  Use the ShootyChute UI for some of these tests.

  1. Test for rotation detection - This may be easiest to do before the SATS-MINI is mounted to the drone.  After arming with the red light flashing flip the device end over end and the SATS-MINI should trigger showing a blue flashing light. You can use a Servo to verify movement.

  2. Test for Free Fall detection - After arming toss the device into the air being careful to not have it rotating.  After about ½ second the SATS-MINI should trigger to a blue light.

  3. Make sure the SATS-MINI IMU is calibrated. The ShootyChute UI top pane note the line Calibration Status says “Calibrated”.  All units are calibrated at the factory and should not need recalibration.  If it does not indicate calibration or you see the Error indicator show that there is a IMU error contact Fruity Chutes for assistance.

  4. With the drone level on the ground using the ShootyChute UI check that the virtual drone should also be level.  

  5. Rotating the drone will cause the virtual drone to rotate.

  6. Test the parachute channel endpoints.  You can toggle the SATS-MINI states using the mode pulldown.  If you have an energetic parachute system like CO2 or Pyro be sure to disconnect these first.  Use a servo to test for channel operation.

  7. If you are using advanced features like altimeter safety or overrides be sure to verify these.

  8. If you are using external trigger input be sure to test again for proper operation.

  9. Dry run your setup - If you are concerned about possible false triggers due to sensitive setup parameters test fly the SATS-MINI on your drone first and make sure the device does not trigger accidentally.  Fly the drone at the edges of the flight envelope to see if you can false trigger the SATS.  If you do see a false trigger then download the flight log to see the conditions.  You may need to adjust the trigger settings.

  10. After testing, download the Log file and verify for expected operation.

Best Practices

  1. Unless you are using an external 5V input power feed make sure you charge the SATS daily before flight. Charging can be done via USB cable to your computer.  Charging takes about 90 minutes. The Yellow charge light will extinguish once charged.

  2. Before flight make sure the SATS-MINI is sufficiently charged.  The SATS-MINI LiPo is sufficient to operate the unit for up to 6 hours of operation (when not using the Nano receiver).  When there is under one hour of battery life left the device will chirp twice per second.  Do not fly if the SATS-MINI is chirping since the battery life may be short.

  3. Check the parachute launcher and connection to the SATS-MINI before flight.

  4. Before takeoff make sure the SATS-MINI is armed (or in safety if used).

    IMPORTANT - The SATS-MINI includes features that allow it to automatically turn on in the armed state and be ready to go when external power is applied via CH3, or CH4.  When power is removed the SATS-MINI can be programmed to automatically turn off after a period of time.  But even while the SATS-MINI has these features it is not set and forget! It is STRONGLY recommended that the pilot always check the SATS-MINI for proper operation before takeoff. If an unrecoverable error is detected the SATS-MINI will hold in the ERROR state and will not monitor the flight.  In this case simply power cycling the SATS-MINI will clear this.  In testing over 1000's of power cycles the odds of this accuring are very small, however it is still best to always have a pre-flight check that the SATS-MINI is ready to go.

  5. After flight disarm the SATS-MINI and turn to save battery and log space.

What To Do After Parachute Deployment

If the SATS-MINI triggers a parachute deployment be sure to disarm the SATS-MINI and download the log file.  The log events will show what condition caused the parachute to eject.  If you like please send the log to Fruity Chutes and we can do a post-deployment analysis to verify operation.  Also helpful would be to indicate the drone type, weight, parachute system and so on.  Also flight conditions.


Contact us if you require any other assistance!


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