> For the complete documentation index, see [llms.txt](https://docs.sky-pulse.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.sky-pulse.org/documentation/technical-specifications/quickstart.md).

# SkyPulse Helios FMU

### Introduction

**SkyPulse Helios** is an integrated avionics and compute stack engineered for next-generation unmanned systems.

At its core, the Helios features a high performance, sensor redundant flight controller paired with an onboard companion computer capable of executing advanced algorithms such as: **Visual Inertial Odometry (VIO**), **SLAM**, **Automatic target recognition (ATR), adaptive feature detection, automatic calibration, interception** and **obstable avoidance.**

Built with a **low SWaP-C** profile and **full NDAA compliance**, Helios delivers enterprise-grade capability while maintaining a compact footprint. 

With native support for **ArduPilot** and **PX4**, integration is easy and plug & play, ensuring seamless compatibility with existing vehicles, ground control stations and software suites.

<figure><img src="https://2346690621-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FnOXDCeV4qoAzHESoDw0I%2Fuploads%2FGY7nsd0NTvcQFW2Ziyra%2FSkyPulseHelios-Rendered.png?alt=media&amp;token=8212335d-2054-49c0-83bf-708732f19796" alt="" width="440"><figcaption><p>SkyPulse Helios FMU</p></figcaption></figure>

### Key Features

**Input voltage:** 5-36v (2-6s battery\*)\
**Output voltage:** Dual 5V high current outputs + 3.3V output\
**Dimensions:** 45x65x25mm (WxLxH)\
**Weight:** 73g\
**Onboard Micro-SD slot for logging**\
**Onboard Buzzer**\
**Onboard RGB LED for status**\
**High performance flight controller running ArduPilot / PX4**\
**Triple redundant IMUs**\
**FRAM for parameters + mission waypoints**\
**Onboard companion computer with 4x A76 cores @** 2.4GHz (CM5)\
**WiFi + BT**

### **Companion computer specs & interfaces**

The Helios is based on the trusted <mark style="color:blue;">**Compute Module 5**</mark> by Raspberry Pi.

{% hint style="info" %}
The companion computer comes pre-flashed with a clean image of Debian Bookworm.&#x20;

Contact us for custom images.
{% endhint %}

The specs of the CM5 are:&#x20;

* 4 / 8GB RAM
* 32 / 64 GB FLASH (Onboard EMMC)
* 4x Arm Cortex-A76 Cores @2.4GHz
* Built-in WiFi & Bluetooth
* 1x USB 2.0
* 2x USB 3.0
* 2x MIPI CSI-2
* Gigabit Ethernet
* µHDMI Output
* Analog Video Output
* PCI-E for AI Accelerators, SDRs, storage and more
* Various GPIOs for servos, actuators
* Up to 26 TOPs of AI compute power (using the [SkyPulse accelerator module](/documentation/technical-specifications/skypulse-neuron-ai-module.md))

{% hint style="info" %}
Helios comes with the EMMC version of the CM5, which is more reliable than the SD card version
{% endhint %}

### **Flight Controller specs & Interfaces**

* **Triple Onboard IMUs:**
  * **Main IMU** - Low drift & high accuracy in harsh vibration environments
  * **Secondary IMU** - High vibration rejection, great temperature stability
  * **Third IMU** - 6 DOF Industrial IMU, extended temperature range

* **Other sensors:**
  * **Compass:** Onboard dedicated compass with accurate heading and extremely low drift
  * **Barometer:** Onboard barometer with centimeter-level accuracy.

* **Interfaces:**

  * 6x UART
  * 8x Motor outputs (DSHOT, PWM, OneShot) - possible to mix and match between protocols
  * 2x CAN bus ports
  * 3x I2C ports (seperate bus)
  * Analog voltage & current sensing
  * Safety switch input
  * RC Input (ELRS, CrossFire, SBUS, FrSky)

* #### **Firmware Compatibility:**
  * Helios fully supports ArduPilot and PX4, custom builds are also supported.
  * Helios FMUs are shipped with ArduCopter by default, PX4 can be flashed via USB.

<div data-full-width="true"><figure><img src="https://2346690621-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FnOXDCeV4qoAzHESoDw0I%2Fuploads%2FCUHp8gg0sUt1p2A5JEPL%2FArduPX4.png?alt=media&amp;token=a5484338-450e-4d6b-8d38-5e6d88d3e1b2" alt="" width="563"><figcaption></figcaption></figure></div>

* #### **Software Compatibility:**
  * Helios can run a wide variety of packages such as: Tensorflow, OpenCV, ROS, as well as other apps from the SkyPulse software stack.
* #### **Communications:**
  * **Whether you are using CrossFire from your existing setup, or DTC's BluSDR line, Helios supports it all.**
  * The SkyPulse FMU was heavily tested with hundreds of flight hours on a variety of communication links, such as: ELRS, CrossFire, DTC, MicroHard, Siyi, FrSky, Futaba, RFD900x, Silvus, Doodle Labs and even Fiber Optics.

### Pinout & connections

The pinout splits into 3 convenient groups:

* Computer interfaces
* Flight controller interfaces
* Power

<figure><img src="https://2346690621-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FnOXDCeV4qoAzHESoDw0I%2Fuploads%2FTtLoX6WGs0o7AseZYmb1%2Ffmubreakout2.png?alt=media&amp;token=5b23eb5a-1948-45e6-a1f0-f620ef9412a4" alt="" width="563"><figcaption></figcaption></figure>

#### Power

The first thing you'd have to do in order to use the Helios is supply it with a suitable power source. \
In most cases, a direct connection to the battery is the best option if you're using up to 6s.

for a direct connection to 8s, an external filter / protection is required due to inductive voltage spikes from the motors.

The Helios supports up to 36v filtered input (and was tested thoroughly on unfiltered 6s voltage), so you don't have to use any external regulators / filters for systems up to 6s.

If you're working with a voltage higher than 36v, make sure your BEC is able to supply adequate current. \
Helios takes up to \~12w of power under full load (and around 7w under moderate load, 2.7w at idle), so we recommend taking a bit of headroom and choosing a BEC capable of delivering over 20 watts.

The power connector used in the Helios is a 2 pin Molex Nano-Fit locking connector (45130-0201).&#x20;

{% hint style="danger" %}
**Make sure you double check the polarity of your wiring! Reversing the polarity will cause damage to the Helios unit.**
{% endhint %}

<figure><img src="https://2346690621-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FnOXDCeV4qoAzHESoDw0I%2Fuploads%2FyWgCYszDSAPpUzS9FU2I%2Fpower2.png?alt=media&amp;token=f6cdbb46-fd4d-4ad7-8fb5-e7840fdf2da5" alt=""><figcaption></figcaption></figure>

#### Flight controller interfaces

The second group of connectors (FMU1 & FMU2) are the actual connectors you'll use to connect to the rest of your avionics, such as telemetry radios, sensors, ESCs and more.

The connectors used for these interfaces are locking Molex Pico-Clasp connectors (501189-3010)

<figure><img src="https://2346690621-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FnOXDCeV4qoAzHESoDw0I%2Fuploads%2F00fRJTAGA8GxvcffQ1Eb%2FSkyPulseFMUPinout.png?alt=media&amp;token=d94ff7e8-7e96-422b-a726-6130d110a10d" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
Channels **1-8** support **PWM, DSHOT, OneSHOT** and **Relay** functions. \
Using **DSHOT** is highly recommended if you're using the Helios stack on a racer / FPV drone.
{% endhint %}

{% hint style="danger" %}
BATT\_VOLT and BATT\_CURR are meant for voltage and current sensing only! \
**Connecting them to any voltage over 3.3V will cause significant damage to your unit.**&#x20;
{% endhint %}

#### Companion computer interfaces

The last group of connectors is the interface for the companion computer.\
Helios breaks out most of the interfaces of the CM5, so integration to other systems based on a Raspberry Pi is basically plug & play.

In most cases, you'll use the J3 (Interface) connector to connect to stuff like radio trasnceivers (using ethernet), connecting to USB cameras, and adding an AI accelerator (like the Helios accelerator module).

For additional GPIOs, more USB ports, UARTs and dual use ports, you can use J4 (GPIO) connector.

<figure><img src="https://2346690621-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FnOXDCeV4qoAzHESoDw0I%2Fuploads%2FbJg1v7Fe5nHZOmtvjyV8%2FCompanion.png?alt=media&amp;token=1ebffabf-508a-4748-9475-f3e7f12c292d" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
For 10/100Mb ethernet, you only have to use 4 pins (TX-, TX+, RX-, RX+)
{% endhint %}

{% hint style="info" %}
CM\_RX & CM\_TX (ttyAMA0) are connected to the fight controller's SERIAL3 port.
{% endhint %}

{% hint style="danger" %}
Pins 25, 28 (VIN) are connected directly to the battery input and are unprotected. \
They are only meant to be used as outputs and should not be used to power the unit.
{% endhint %}

#### Serial port mapping

|  UART | Ardupilot Serial | PX4 Serial |      Recommended Function     | Flow Control |
| :---: | :--------------: | :--------: | :---------------------------: | :----------: |
| UART2 |     Serial 1     | /dev/ttyS0 |         Main Telemetry        |      Yes     |
| UART3 |     Serial 2     | /dev/ttyS1 |           GPS Module          |      Yes     |
| UART4 |     Serial 3     | /dev/ttyS2 |   Helios companion computer   |      No      |
| UART6 |     Serial 4     | /dev/ttyS3 | Secondary Telemetry / Payload |      Yes     |
| UART7 |     Serial 5     | /dev/ttyS4 |     ESC Telemetry / Debug     |      No      |
| UART8 |     Serial 6     | /dev/ttyS5 |          RC Receiver          |      No      |

#### One pager

The pinout and basic specs are attached here, in a single page PDF:

{% file src="/files/wMSff1AhCrZrNfW83YRI" %}

## Manufacturing & NDAA Compliance

{% hint style="success" %}
All of our hardware is 100% NDAA compliant, based on high quality non-Chinese components. Every module goes through rigorous testing to ensure the best quality for our users.
{% endhint %}

<figure><img src="https://2346690621-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FnOXDCeV4qoAzHESoDw0I%2Fuploads%2Fe3GsC8DH98J6aIGomAWG%2FNDAA.png?alt=media&amp;token=67d659c5-a10d-463c-843b-45943c2c9a60" alt=""><figcaption></figcaption></figure>