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

Resources to get started with the SATS-MINI

SATS-MINI Product Guide with VTOL Support PDF

SATS-MINI Quick Start Guide PDF

SATS-MINI Users and Programming Guide with VTOL PDF

Purchase the SATS-MINI

SATS-MINI Software Downloads
Current Version: 1.3.6

Download Version 1.3.6 - Current Production Release

Updates for version 1.3.6 - This is a critical update - This update adds support to the new V2.3 SATS-MINI hardware that features an upgraded barmetric sensor.  It also fixes a bug in the Real Time Clock library that was causing occational error conditions during startup.  The startup error caused the real time clock I to fail to initialize and instead go to the error state with a pulsing purple light.  The probability of this error was fairly low overall, perhaps one in 600 startups.  However there are some devices in the field where the chances of the startup error are much higher, perhaps 5%.  A side benifit is the startup time is faster and more consistent.

IMPORTANT - Best Practices - 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. However, 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 the error. In testing over thousands of power cycles, the odds of this occurring are very small; however, it is still best to always have a pre-flight check to ensure the SATS-MINI is ready to go.

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

Previous SATS-MINI Software Releases

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.

Diagram of SATS-MINI next to the real device.

IMPORTANT - READ FIRST FOR NEW SATS-MINI USERS - 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, 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!

The Sentinel Automatic Trigger System (SATS-MINI) has many complex programmable features that can be setup using the Shooty Chute Windows UI program. Once the configuration is uploaded, the only thing required to fly and protect your drone is to turn on the SATS-MINI. Before you fly, ensure that 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 your 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 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 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 launchers 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 this 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 a PWM trigger signal so you can remote eject the parachute from the Skycat rescue radio. If the Nano is not installed, 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 almost all drones, such as 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 on how to use the program.

SATS-MINI Basic Operation

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

Diagram of the SATS-MINI

To turn on the SATS-MINI press and hold the System Mode button for 2 seconds. Once the indicator lights come on, release the button. 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 before changing.

To Turn Off the SATS-MINI, quickly press and release the System Mode button. The SATS-MINI will beep twice: high then low. After this, 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 states. The beeper will sound as well.

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 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 will 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 restarting, 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 this is needed.

Updating the Firmware to a New Version

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, and 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.
  • Before upgrading the SATS-MINI, install the new Shooty Chute UI. You will need this in order to complete the Firmware upgrade. The new UI will not work with pre 1.2.X firmware, so do not connect to the SATS-MINI before upgrading the firmware to the latest version.

In order to install:

  1. Power-up the SATS-MINI and connect the USB cable. You should hear a beep, indicating 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.

  3. To load the firmware, you first 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 (RST). 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 ATS.UF2 file into the FEATHERBOOT folder. You should see the red light flicker, and the SATS-MINI will restart. 

  5. The SATS-MINI will power up in the Error state (Purple pulsing). The UI will tell you you need 

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

To Configure the SATS-MINI

For detailed information about setting up and programming the SATS-MINI download the SATS-MINI Users and Programming Guide with VTOL PDF

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. 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 direction is up. The calibration procedure allows you to mount the SATS-MINI on your drone in any imaginable orientation. Follow these steps:

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

  2. Turn on the SATS-MINI and first initialize the IMU magnetometer by rotating the SATS-MINI (or rotating 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 precisely 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. 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 will be exactly matched by the UI Drone. 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.

Important: When using the Fixed Angle detection the calibration, offset is not considered. The SATS-MINI must be mounted in the native IMU orientation onto the aircraft. See the SATS-MINI Product Guide for details.


If you have a parachute deployment, the log file is a critical tool to determine the exact cause of the drone failure. As such, 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, such as low power, are logged to the onboard Flash memory. The Flash memory will hold approximately 6 hours of detailed log data when running at 10Hz. Once at 30 minutes or less log space available, only critical events are logged. To transfer 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.

New! - If you enable Terse Logging, only key events are logged for each flight and take very little log space, so many thousands of flights can be logged. And if you have a parachute trigger the detail logging immediatly before and after the parachute trigger are saved to the log file. Also enable Auto Erase to automatically erase the log file once it is full.

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. Additionally, the SATS-MINI can be driven by the Parachute Channels output of the Pixhawk to provide external trigger of the SATS-MINI and eject the parachute. The default SATS-MINI configuration has CH4 setup for external trigger 2000us, 20% tolerance. The Pixhawk parachute output also uses a 2000us PWM pulse width. In addition to this, the Pixhawk 5V power pin on the Parachute output channel will 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 is not yet merged into an official branch (V1.10 is the latest, but does not have support), but it is in Master. Here is the documentation on how to setup Flight Termination: - General article about flight termination done by the PX4 firmware - External ATS Integration to support Flight Termination. This lets the SATS-MINI stop the rotors. Connect one of the PWM parachute out channels to Aux5 or Main5. Termination happens when the SATS-MINI assets a 2000us signal (135 degrees). - Bitbucket pull request outlining some of the details.

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 Termination supported, but there has not been any effort yet to complete this. Here is the request:

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

Use a Relay for Flight Termination - It's possible to use an external relay to cut power to the autopilot or the ESC power to stop the rotors. Here is a schematic to do this. It works with the DJI A3 autopilot.

SATS-MINI Configuration with Pixhawk and Flight Termination Relay.pdf

Sample SATS-MINI configuration with flight termination support - SATS-MINI Configuration XML - Right click and save to your hard drive. Then upload to the SATS-MINI. Be sure to thoroughly test your setup.

Testing and Verification

After setting up your SATS-MINI, be sure to test and verify all operations. Use the Shooty Chute 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. 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 not to rotate it. After about ½ second, the SATS-MINI should trigger to a blue light.

  3. Make sure the SATS-MINI IMU is calibrated. In the Shooty Chute UI main panel, note that 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 Shooty Chute UI, check that the virtual drone is also 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 an 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, ensure 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 remaining, the device will chirp twice per second. Do not fly if the SATS-MINI is chirping since the battery life may be too 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. However, 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 thousands of power cycles, the odds of this occurring are very small. However, it is still best to always have a pre-flight check to ensure the SATS-MINI is ready to go.

  5. After flight, disarm and turn off the SATS-MINI 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. In this case, it would be helpful to indicate the drone type, weight, parachute system, etc., as well as flight conditions.

Contact us if you require any assistance.

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