> For the complete documentation index, see [llms.txt](https://px4.gitbook.io/px4-user-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://px4.gitbook.io/px4-user-guide/drone_parts/flight_controller/autopilot_discontinued/omnibus_f4_sd.md).

# Omnibus F4 SD

:::warning This flight controller has been [discontinued](/px4-user-guide/drone_parts/flight_controller/autopilot_experimental.md) and is no longer commercially available. :::

:::warning PX4 does not manufacture this (or any) autopilot. Contact the manufacturer for support or compliance issues. :::

The *Omnibus F4 SD* is a controller board designed for racers. In contrast to a typical racer board it has some additional features, such as an SD card and a faster CPU.

![](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-a4bb1c373dafeac6bd6bfb70139ca53583bdee8b%2Fboard.jpg?alt=media)

These are the main differences compared to a [Pixracer](/px4-user-guide/drone_parts/flight_controller/autopilot_pixhawk_standard/pixracer.md):

* Lower price
* Fewer IO ports (though it's still possible to attach a GPS or a Flow sensor for example)
* Requires external pull up resistor on the I2C bus for external GPS, see [I2C](#i2c) below.
* Less RAM (192 KB vs. 256 KB) and FLASH (1 MB vs. 2 MB)
* Same board dimensions as a *Pixracer*, but slightly smaller form factor (because it has less connectors)
* Integrated OSD (not yet implemented in software)

:::tip All the usual PX4 features can still be used for your racer! :::

:::note This flight controller is [manufacturer supported](/px4-user-guide/drone_parts/flight_controller/autopilot_manufacturer_supported.md). :::

## Key Features

* Main System-on-Chip: [STM32F405RGT6](https://www.st.com/en/microcontrollers/stm32f405rg.html)
  * CPU: 168 MHz ARM Cortex M4 with single-precision FPU
  * RAM: 192 KB SRAM
  * FLASH: 1 MB
* Standard racer form factor: 36x36 mm with standard 30.5 mm hole pattern
* MPU6000 Accel / Gyro
* BMP280 Baro (not all boards have it mounted)
* microSD (for logging)
* Futaba S.BUS and S.BUS2 / Spektrum DSM2 and DSMX / Graupner SUMD / PPM input / Yuneec ST24
* OneShot PWM out (configurable)
* Built-in current sensor
* Built-in OSD chip (AB7456 via SPI)

## Where to Buy

The board is produced by different vendors, with some variations (e.g. with or without a barometer).

:::tip PX4 is compatible with boards that support the Betaflight OMNIBUSF4SD target (if *OMNIBUSF4SD* is present on the product page the board should work with PX4). :::

:::tip Any Omnibus F4 labeled derivative (e.g. clone) should work as well. However, power distribution on these boards is of varying quality. :::

These are the boards tested and known to work:

* [Hobbywing XRotor Flight Controller F4](https://www.hobbywing.com/en/products/info.html?id=164)

  :::note This board fits on top of the [Hobbywing XRotor Micro 40A 4in1 ESC](https://www.hobbywing.com/en/products/info.html?id=116) without soldering. This ESC board also provides power for the Omnibus board. :::

  Purchase from:

  * [Hobbywing XRotor F4 Flight Controller w/OSD](https://www.getfpv.com/hobbywing-xrotor-f4-flight-controller-w-osd.html) (getfpv)
* Original Airbot Omnibus F4 SD

  Purchase from:

  * [Airbot (CN manufacturer)](https://store.myairbot.com/omnibusf4prov3.html)
  * [Ready To Fly Quads (US reseller)](https://quadsrtf.com/product/flip-32-f4-omnibus-rev-2/)

Accessories include:

* [ESP8266 WiFi Module](/px4-user-guide/drone_parts/peripherals/telemetry/telemetry_wifi/esp8266_wifi_module.md) for MAVLink telemetry. You need to connect these pins: GND, RX, TX, VCC and CH-PD (CH-PD to 3.3V). The baud rate is 921600.

## Connectors

Boards from different vendors (based on this design) can have significantly different layout. Layouts/Silkscreens for various versions are shown below.

### Airbot Omnibus F4 SD

Below are silkscreens for the Airbot Omnibus F4 SD (V1), showing both top and bottom.

![Omnibus F4 SD v1 Silkscreen Top](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-daf813a1668c4685e310433747ef32ecfa6d99d6%2Fsilk-top.jpg?alt=media) ![Omnibus F4 SD v1 Silkscreen Bottom](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-282a4bb8e5e00d92227029d4c8f55a40495d63ba%2Fsilk-bottom.jpg?alt=media)

### Hobbywing XRotor Flight Controller F4

Below are silkscreens for the Hobbywing XRotor Flight Controller F4.

![Hobbywing XRotor Flight Controller F4 Silkscreen](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-cfd4a29aed7b37c4606f8e6aebe0a2160e7afa89%2Fhobbywing_xrotor_silk.png?alt=media)

## Pinouts

### Radio Control

RC is connected to one of the following ports:

* UART1
* SBUS/PPM port (via inverter, internally goes to UART1)

:::note Some Omnibus F4 boards have a jumper connecting either or both the MCU SBUS and PPM to a single pin header. Set your jumper or solder bridge to the appropriate MCU pin before use. :::

### UARTs

* UART6: GPS port

  * TX: MCU pin PC6
  * RX: MCU pin PC7
  * Airbot Omnibus F4 SD Pinout is on Port J10 (TX6/RX6):

  ![Omnibus F4 SD UART6](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-1d1cc0a56e230f32be8f7ba2e34e6578e431a73c%2Fuart6.jpg?alt=media)
* UART4

  * TX: MCU pin PA0
  * RX: MCU pin PA1
  * 57600 baud
  * This can be configured as the `TELEM 2` port.
  * Airbot Omnibus F4 SD Pinout:
    * TX: RSSI pin
    * RX: PWM out 5

  ![Omnibus F4 SD UART4](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-2ee48cd3bf6a4f5fa64164a0e7e8bc08c4e866ca%2Fuart4.jpg?alt=media)

  ![Omnibus F4 SD UART4 Top](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-fce23cb016b311158d7cca4d1e342ff5225e77dd%2Fuart4-top.jpg?alt=media)

### I2C

There is one I2C port available via:

* SCL: MCU pin PB10 (might be labeled as TX3)
* SDA: MCU pin PB11 (might be labeled as RX3)

:::note You will need external pullups on both signals (clock and data). You can use 2.2k pullups for example to attach an external mag. :::

* Airbot Omnibus F4 SD Pinout is on Port J10 (SCL \[clock] / SCA \[data]): ![](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-1d1cc0a56e230f32be8f7ba2e34e6578e431a73c%2Fuart6.jpg?alt=media)

Here is an example implementation. I used a Spektrum plug to get 3.3v from the DSM port, connecting only 3.3v + to each line via 2.2k resistor.

![Omnibus F4 SD Pullup](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-74a26d680d7b0042476ba26396cfb66019b24b54%2Fpullup-schematic.jpg?alt=media)

![Omnibus F4 SD Pullup Implementation](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-3e627752b6780d934f6e3a7660abedcbd36c3230%2Fpullup.jpg?alt=media)

## Serial Port Mapping

| UART   | Device     | Port     |
| ------ | ---------- | -------- |
| USART1 | /dev/ttyS0 | SerialRX |
| USART4 | /dev/ttyS1 | TELEM1   |
| USART6 | /dev/ttyS2 | GPS      |

## RC Telemetry

The Omnibus supports telemetry to the RC Transmitter using [FrSky Telemetry](/px4-user-guide/drone_parts/peripherals/frsky_telemetry.md) or [CRSF Crossfire Telemetry](#crsf_telemetry).

### CRSF Crossfire Telemetry

[TBS CRSF Telemetry](/px4-user-guide/drone_parts/peripherals/crsf_telemetry.md) may be used to send telemetry data from the flight controller (the vehicle's attitude, battery, flight mode and GPS data) to an RC transmitter such as a Taranis.

Benefits over [FrSky telemetry](/px4-user-guide/drone_parts/peripherals/frsky_telemetry.md) include:

* Only a single UART is needed for RC and telemetry.
* The CRSF protocol is optimized for low latency.
* 150 Hz RC update rate.
* The signals are uninverted and thus no (external) inverter logic is required.

:::note If you use CRSF Telemetry you will need to build custom PX4 firmware. By contrast, FrSky telemetry can use prebuilt firmware. :::

For Omnibus we recommend the [TBS Crossfire Nano RX](http://team-blacksheep.com/products/prod:crossfire_nano_rx), since it is specifically designed for small Quads.

On the handheld controller (e.g. Taranis) you will also need a [Transmitter Module](http://team-blacksheep.com/shop/cat:rc_transmitters#product_listing). This can be plugged into the back of the RC controller.

:::note The referenced links above contains the documentation for the TX/RX modules. :::

#### Setup

Connect the Nano RX and Omnibus pins as shown:

| Omnibus UART1 | Nano RX |
| ------------- | ------- |
| TX            | Ch2     |
| RX            | Ch1     |

Next update the TX/RX modules to use the CRSF protocol and set up telemetry. Instructions for this are provided in the [TBS Crossfire Manual](https://www.team-blacksheep.com/tbs-crossfire-manual.pdf) (search for 'Setting up radio for CRSF').

#### PX4 CRSF Configuration

You will need to build custom firmware to use CRSF. For more information see [CRSF Telemetry](/px4-user-guide/drone_parts/peripherals/crsf_telemetry.md#px4-configuration).

## Schematics

The schematics are provided by [Airbot](https://myairbot.com/): [OmnibusF4-Pro-Sch.pdf](http://bit.ly/obf4pro).

## PX4 Bootloader Update

The board comes pre-installed with [Betaflight](https://github.com/betaflight/betaflight/wiki). Before PX4 firmware can be installed, the *PX4 bootloader* must be flashed. Download the [omnibusf4sd\_bl.hex](https://github.com/PX4/PX4-user_guide/raw/main/assets/flight_controller/omnibus_f4_sd/omnibusf4sd_bl_d52b70cb39.hex) bootloader binary and read [this page](/px4-user-guide/advanced_config/bootloader_update_from_betaflight.md) for flashing instructions.

## Building Firmware

To [build PX4](/px4-user-guide/development/getting_started/building_px4.md) for this target:

```
make omnibus_f4sd_default
```

## Installing PX4 Firmware

You can use either pre-built firmware or your own custom firmware.

:::warning\
If you use [CRSF Telemetry](/px4-user-guide/drone_parts/peripherals/crsf_telemetry.md#px4-configuration) in your radio system, as describe above, then you must use custom firmware. :::

The firmware can be installed in any of the normal ways:

* Build and upload the source

  ```
  make omnibus_f4sd_default upload
  ```
* [Load the firmware](/px4-user-guide/config/firmware.md) using *QGroundControl*.

## Configuration

In addition to the [basic configuration](/px4-user-guide/config.md), the following parameters are important:

| Parameter                                                                             | Setting                                                                                                                 |
| ------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------- |
| [SYS\_HAS\_MAG](/px4-user-guide/advanced_config/parameter_reference.md#SYS_HAS_MAG)   | This should be disabled since the board does not have an internal mag. You can enable it if you attach an external mag. |
| [SYS\_HAS\_BARO](/px4-user-guide/advanced_config/parameter_reference.md#SYS_HAS_BARO) | Disable this if your board does not have a barometer.                                                                   |

## Further Info

[This page](https://blog.dronetrest.com/omnibus-f4-flight-controller-guide/) provides a good overview with pinouts and setup instructions.