> For the complete documentation index, see [llms.txt](https://docs.auterion.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.auterion.com/hardware-integration/skynode/peripherals/adapter-boards.md).

# Pixhawk Adapter Board

The Pixhawk adapter board is used to break out the Skynode flight control interfaces on J3 and J4 to connectors and pinouts compatible to the [Pixhawk-standard](https://pixhawk.org/standards/).

{% hint style="danger" %}
The voltage levels for all signals brought out from the FMU to the Pixhawk Adapter Board are either **5V** or **3.3V** compliant. Refer to the [table](#pinouts) below to check the voltage levels of specific pins. Exceeding these voltages will permanently damage the Flight Management Unit inside Skynode.
{% endhint %}

![](/files/0kLtBT5rOF4wYf9qBigf)

{% file src="/files/qUSzZmwQG7MdtPXGkPt7" %}
3D model mockup
{% endfile %}

## Connector Locations

![](/files/wV2eLPaVoQCxAacRlcaI)

## Power Domains and Limits

| Power Rail          | Total Current Limit          | Powered Connectors                      |
| ------------------- | ---------------------------- | --------------------------------------- |
| VDD\_5V\_PERIPH     | 1.5A                         | <p>SPI, TELEM3,<br>GPS2, CAN2, I2C2</p> |
| VDD\_5V\_HIPOWER    | 1A                           | TELEM1                                  |
| VDD\_5V\_CAN1\_GPS1 | 0.45A                        | GPS1, CAN1, I2C1                        |
| VDD\_5V\_SBUS\_RC   | 0.25A                        | SBUS RC                                 |
| VDD\_SERVO          | Must be externally provided! | FMU, IO                                 |

## Schematic

{% file src="/files/OABifeqgGHExA2jH2kIF" %}
Pixhawk Adapter RC05
{% endfile %}

{% file src="/files/QaA8ymACWFPqJrbp7rJV" %}
Pixhawk Adapter RC06
{% endfile %}

{% file src="/files/gejtYrLAmpr5kos6tqoQ" %}
Pixhawk Adapter RC07
{% endfile %}

{% hint style="info" %}
Take a look at the [Skynode Harwdare Revision 11 release notes](broken://spaces/6YcltiieOK2HPGwsTPS0/pages/YYuLh8vK0RjE9UZHkmYw) for details about the changes.
{% endhint %}

## Connectors

<table data-header-hidden><thead><tr><th width="150">ID</th><th width="150">Name</th><th>Connector</th><th>Description</th></tr></thead><tbody><tr><td>ID</td><td>Name</td><td>Connector</td><td>Description</td></tr><tr><td>J11</td><td>Primary</td><td>Molex Pico-Clasp<br>5015714007</td><td>Connect to Skynode Primary (J4)</td></tr><tr><td>J12</td><td>Telem 1</td><td><p>JST GH 6-pin</p><p>SM06B-GHS-TB</p></td><td></td></tr><tr><td>J13</td><td>GPS 1</td><td><p>JST GH 10-pin</p><p>SM10B-GHS-TB</p><p>(until rev 5 included)<br><br>JST GH 11-pin</p><p>SM11B-GHS-TB<br>(from rev 6 included)</p></td><td>Primary GPS with external compass, safety switch and led</td></tr><tr><td>J14</td><td>CAN 1</td><td><p>JST GH 4-pin</p><p>SM04B-GHS-TB</p></td><td></td></tr><tr><td>J15</td><td>FMU</td><td><p>Pin Header</p><p>TSW-108-08-G-T-RA</p></td><td>PWM channels from FMU, input capable</td></tr><tr><td>J16</td><td>SBUS RC</td><td><p>JST GH 3-pin</p><p>SM03B-GHS-TB</p></td><td>SBUS protocol RC input</td></tr><tr><td>J18</td><td>I2C 1</td><td><p>JST GH 4-pin</p><p>SM04B-GHS-TB</p></td><td></td></tr></tbody></table>

<table data-header-hidden><thead><tr><th width="150">ID</th><th width="150">Name</th><th>Connector</th><th>Description</th></tr></thead><tbody><tr><td>ID</td><td>Name</td><td>Connector</td><td>Description</td></tr><tr><td>J21</td><td>Secondary</td><td>Molex Pico-Clasp<br>5015714007</td><td>Connect to Skynode Secondary (J3)</td></tr><tr><td>J22</td><td>SBUS OUT</td><td><p>JST GH 3-pin</p><p>SM03B-GHS-TB</p></td><td>SBUS output</td></tr><tr><td>J23</td><td>GPS 2</td><td><p>JST GH 6-pin</p><p>SM06B-GHS-TB</p></td><td>Redundant GPS</td></tr><tr><td>J24</td><td>SPI</td><td><p>JST GH 11-pin</p><p>SM11B-GHS-TB</p></td><td></td></tr><tr><td>J25</td><td>IO</td><td><p>Pin Header</p><p>TSW-108-08-G-T-RA</p></td><td>PWM channels from IO</td></tr><tr><td>J26</td><td>Telem 3</td><td><p>JST GH 6-pin</p><p>SM06B-GHS-TB</p></td><td></td></tr><tr><td>J27</td><td>CAN 2</td><td><p>JST GH 4-pin</p><p>SM04B-GHS-TB</p></td><td></td></tr><tr><td>J28</td><td>I2C 2</td><td><p>JST GH 4-pin</p><p>SM04B-GHS-TB</p></td><td></td></tr></tbody></table>

## Pinouts

### Telem 1 (J12)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="164">Name</th><th width="150">Dir</th><th width="200">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_HIPOWER</td><td></td><td>5V</td><td>5V supply for peripherals, max. 1.0A (fused)</td></tr><tr><td>2</td><td>UART7_TX</td><td>OUT</td><td>3.3V</td><td>Telem 1 TX</td></tr><tr><td>3</td><td>UART7_RX</td><td>IN</td><td>3.3V</td><td>Telem 1 RX</td></tr><tr><td>4</td><td>UART7_CTS</td><td>IN</td><td>3.3V</td><td>Telem 1 CTS</td></tr><tr><td>5</td><td>UART7_RTS</td><td>OUT</td><td>3.3V</td><td>Telem 1 RTS</td></tr><tr><td>6</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

### GPS 1(J13)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="197">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_CAN1_GPS1</td><td></td><td>5V</td><td>5V supply for primary GPS and CAN interface</td></tr><tr><td>2</td><td>USART1_TX</td><td>OUT</td><td>3.3V</td><td>GPS 1 TX</td></tr><tr><td>3</td><td>USART1_RX</td><td>IN</td><td>3.3V</td><td>GPS 1 RX</td></tr><tr><td>4</td><td>I2C1_SCL</td><td>I/O</td><td>3.3V</td><td>I2C SCL for external magnetometer</td></tr><tr><td>5</td><td>I2C1_SDA</td><td>I/O</td><td>3.3V</td><td>I2C SDA for external magnetometer</td></tr><tr><td><mark style="color:red;"><strong>6</strong></mark></td><td><mark style="color:red;">GPS_PPS</mark></td><td><mark style="color:red;">IN</mark></td><td><mark style="color:red;">3.3V</mark></td><td><mark style="color:red;">PPS signal from GPS module</mark></td></tr><tr><td>7</td><td>FMU_IO_SAFETY_SWITCH_IN</td><td>IN</td><td>3.3V</td><td>Safety switch state input</td></tr><tr><td>8</td><td>FMU_IO_nSAFETY_SWITCH_LED_OUT</td><td>OUT</td><td>3.3V</td><td>Safety switch led output</td></tr><tr><td>9</td><td>FMU_VDD_3V3</td><td>OUT</td><td>3.3V</td><td>3.3V supply for peripherals, max 50mA</td></tr><tr><td>10</td><td>BUZZER_1_INV</td><td>OUT</td><td></td><td>Buzzer output (open drain)</td></tr><tr><td>11</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

{% hint style="info" %}
I2C lines are pulled up with 1kΩ in Skynode. External pull up resistors shall not be added.
{% endhint %}

{% hint style="info" %}
The Buzzer is disabled by default since it can draw significant current which may lead to brown-outs of other sensors on the same power rail. You can enable it by resetting the parameter `CBRK_BUZZER` if you are sure that it does NOT cause issues on your airframe.
{% endhint %}

{% hint style="info" %}
The highlighted pin 6 was added in rev 6 of the Pixhawk Adapter Board, to ensure compatibility with the PX4 F9P GPS module. For backwards compatibility with the [Freefly RTK GPS module](/hardware-integration/skynode/peripherals/freefly-rtk-gps.md), a custom cable needs to be made.
{% endhint %}

### CAN 1 (J14)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="187">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_CAN1_GPS1</td><td></td><td>5V</td><td>5V supply for primary GPS and CAN interface</td></tr><tr><td>2</td><td>CAN1_P</td><td>I/O</td><td>CAN-H</td><td>FMU CAN 1</td></tr><tr><td>3</td><td>CAN1_N</td><td>I/O</td><td>CAN-L</td><td>FMU CAN 1</td></tr><tr><td>6</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

{% hint style="warning" %}
CAN bus termination on Skynode changed in RC11.\
Prior to [rev 11](https://github.com/Auterion/public-gitbook-documentation/blob/main/hardware-integration/skynode/peripherals/broken-reference/README.md), Skynode has a 120Ω bus termination resistor inside, with no CAN termination on the Pixhawk Adapter Boards (until rev 5 included). This configuration assumed that Skynode was at the end of the bus.\
Rev 11 and onwards has the 120Ω bus termination resistor on the Pixhawk Adapter Boards (from rev 6 included), without built-in termination inside of Skynode. When designing [a wire harness](/hardware-integration/airframe-integration/wiring-without-breakout-boards.md) instead of using the Pixhawk Adapter Boards, usage of 120Ω termination resistors at both ends of the bus is mandatory, following ISO 11898..
{% endhint %}

### FMU - ESC and Servo (J15)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="150">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>PWM/OneShot</th><th>DShot</th><th>Shared with PPB</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td><p>PWM/</p><p>OneShot</p></td><td>DShot</td><td>Shared with<br>PPB</td></tr><tr><td>1</td><td>FMU_CH1</td><td>I/O</td><td>3.3V</td><td>Yes</td><td>Yes</td><td></td></tr><tr><td>2</td><td>FMU_CH2</td><td>I/O</td><td>3.3V</td><td>Yes</td><td>Yes</td><td></td></tr><tr><td>3</td><td>FMU_CH3</td><td>I/O</td><td>3.3V</td><td>Yes</td><td>Yes</td><td></td></tr><tr><td>4</td><td>FMU_CH4</td><td>I/O</td><td>3.3V</td><td>Yes</td><td>Yes</td><td></td></tr><tr><td>5</td><td>FMU_CH5</td><td>I/O</td><td>3.3V</td><td>Yes</td><td>Yes</td><td></td></tr><tr><td>6</td><td>FMU_CH6</td><td>I/O</td><td>3.3V</td><td>Yes</td><td>Yes</td><td></td></tr><tr><td>7</td><td>FMU_CH7</td><td>I/O</td><td>3.3V</td><td>Yes</td><td></td><td>Yes</td></tr><tr><td>8</td><td>FMU_CH8</td><td>I/O</td><td>3.3V</td><td>Yes</td><td></td><td>Yes</td></tr></tbody></table>

### SBUS RC (J16)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="150">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_SBUS_RC</td><td></td><td>5V</td><td>5V supply for RC receiver, max 250mA</td></tr><tr><td>2</td><td>IO_SBUS_INPUT</td><td>IN</td><td>3.3V</td><td>SBUS protocol RC input</td></tr><tr><td>3</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

### I2C 1 (J18)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="189">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_CAN1_GPS1</td><td></td><td>5V</td><td>5V supply for primary GPS and CAN interface</td></tr><tr><td>2</td><td>I2C1_SCL</td><td>I/O</td><td>3.3V</td><td>I2C SCL for external peripherals</td></tr><tr><td>3</td><td>I2C1_SDA</td><td>I/O</td><td>3.3V</td><td>I2C SDA for external peripherals</td></tr><tr><td>6</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

{% hint style="info" %}
I2C lines are pulled up with 1kΩ in Skynode. External pull up resistors shall not be added.
{% endhint %}

### SBUS OUT (J22)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="174">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_SBUS_RC</td><td></td><td></td><td>Not connected</td></tr><tr><td>2</td><td>IO_SBUS_OUTPUT</td><td>OUT</td><td>3.3V</td><td>SBUS protocol output</td></tr><tr><td>3</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

### GPS 2 (J23)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="162">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_PERIPH</td><td></td><td>5V</td><td>5V supply for peripherals</td></tr><tr><td>2</td><td>USART8_TX</td><td>OUT</td><td>3.3V</td><td>GPS 2 TX</td></tr><tr><td>3</td><td>USART8_RX</td><td>IN</td><td>3.3V</td><td>GPS 2 RX</td></tr><tr><td>4</td><td>I2C2_SCL</td><td>I/O</td><td>3.3V</td><td>I2C SCL for external magnetometer</td></tr><tr><td>5</td><td>I2C2_SDA</td><td>I/O</td><td>3.3V</td><td>I2C SDA for external magnetometer</td></tr><tr><td>6</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

{% hint style="info" %}
I2C lines are pulled up with 1kΩ in Skynode. External pull up resistors shall not be added.
{% endhint %}

### SPI (J24)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="157">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_PERIPH</td><td></td><td></td><td></td></tr><tr><td>2</td><td>SPI6_SCK</td><td>OUT</td><td>3.3V</td><td>SPI Clock</td></tr><tr><td>3</td><td>SPI6_MISO</td><td>IN</td><td>3.3V</td><td>SPI MISO</td></tr><tr><td>4</td><td>SPI6_MOSI</td><td>OUT</td><td>3.3V</td><td>SPI MOSI</td></tr><tr><td>5</td><td>SPI6_nCS1</td><td>OUT</td><td>3.3V</td><td>Chip select 1</td></tr><tr><td>6</td><td>NC</td><td></td><td></td><td></td></tr><tr><td>7</td><td>SPI6_nSYNC</td><td>OUT</td><td>3.3V</td><td>Sync signal</td></tr><tr><td>8</td><td>SPI6_DRDY1</td><td>IN</td><td>3.3V</td><td>Data ready 1</td></tr><tr><td>9</td><td>NC</td><td></td><td></td><td></td></tr><tr><td>10</td><td>SPI6_nRESET</td><td>OUT</td><td>3.3V</td><td>Reset</td></tr><tr><td>11</td><td>GND</td><td></td><td></td><td></td></tr></tbody></table>

### IO - ESC and Servo (J25)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="150">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>PWM/OneShot</th><th>DShot</th><th>Shared withPPB</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td><p>PWM/</p><p>OneShot</p></td><td>DShot</td><td><p>Shared with</p><p>PPB</p></td></tr><tr><td>1</td><td>IO_CH1</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr><tr><td>2</td><td>IO_CH2</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr><tr><td>3</td><td>IO_CH3</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr><tr><td>4</td><td>IO_CH4</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr><tr><td>5</td><td>IO_CH5</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr><tr><td>6</td><td>IO_CH6</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr><tr><td>7</td><td>IO_CH7</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr><tr><td>8</td><td>IO_CH8</td><td>OUT</td><td>3.3V</td><td>Yes</td><td></td><td></td></tr></tbody></table>

### Telem 3 (J26)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="169">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_PERIPH</td><td></td><td>5V</td><td>5V supply for peripherals</td></tr><tr><td>2</td><td>USART2_TX</td><td>OUT</td><td>3.3V</td><td>Telem 3 TX</td></tr><tr><td>3</td><td>USART2_RX</td><td>IN</td><td>3.3V</td><td>Telem 3 RX</td></tr><tr><td>4</td><td>NC</td><td></td><td></td><td></td></tr><tr><td>5</td><td>NC</td><td></td><td></td><td></td></tr><tr><td>6</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

### CAN 2 (J27)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="158">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_PERIPH</td><td></td><td>5V</td><td>5V supply for peripherals</td></tr><tr><td>2</td><td>CAN2_P</td><td>I/O</td><td>CAN-H</td><td>FMU CAN 2</td></tr><tr><td>3</td><td>CAN2_N</td><td>I/O</td><td>CAN-L</td><td>FMU CAN 2</td></tr><tr><td>6</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

{% hint style="warning" %}
CAN bus termination on Skynode changed in RC11.\
Prior to [rev 11](https://github.com/Auterion/public-gitbook-documentation/blob/main/hardware-integration/skynode/peripherals/broken-reference/README.md), Skynode has a 120Ω bus termination resistor inside, with no CAN termination on the Pixhawk Adapter Boards (until rev 5 included). This configuration assumed that Skynode was at the end of the bus.\
Rev 11 and onwards has the 120Ω bus termination resistor on the Pixhawk Adapter Boards (from rev 6 included), without built-in termination inside of Skynode. When designing [a wire harness](/hardware-integration/airframe-integration/wiring-without-breakout-boards.md) instead of using the Pixhawk Adapter Boards, usage of 120Ω termination resistors at both ends of the bus is mandatory, following ISO 11898.
{% endhint %}

### I2C 2 (J28)

<table data-header-hidden><thead><tr><th width="150">Pin</th><th width="156">Name</th><th width="150">Dir</th><th width="150">Lvl</th><th>Function</th></tr></thead><tbody><tr><td>Pin</td><td>Name</td><td>Dir</td><td>Lvl</td><td>Function</td></tr><tr><td>1</td><td>VDD_5V_PERIPH</td><td></td><td>5V</td><td>5V supply for peripherals</td></tr><tr><td>2</td><td>I2C2_SCL</td><td>I/O</td><td>3.3V</td><td>I2C SCL for external peripherals</td></tr><tr><td>3</td><td>I2C2_SDA</td><td>I/O</td><td>3.3V</td><td>I2C SDA for external peripherals</td></tr><tr><td>6</td><td>GND</td><td></td><td></td><td>Ground</td></tr></tbody></table>

{% hint style="info" %}
I2C lines are pulled up with 1kΩ in Skynode. External pull up resistors shall not be added.
{% endhint %}