# SIYI N7 Flight Controller

The SIYI N7 flight controller is sold by a range of
resellers, linked from https://siyi.biz

## Features

 - STM32H743 microcontroller
 - ICM20689 and BMI088 IMUs
 - internal heater for IMU temperature control
 - internal vibration isolation for IMUs
 - MS5611 SPI barometer
 - builtin IST8310 compass
 - microSD card slot
 - 4 UARTs plus USB
 - 13 PWM outputs
 - I2C and CAN ports
 - RCIN port
 - external safety Switch
 - voltage monitoring for servo rail and Vcc
 - power input port for external power bricks

## Pinout

## UART Mapping

 - SERIAL0 -> USB
 - SERIAL1 -> UART2 (Telem1)
 - SERIAL2 -> unused
 - SERIAL3 -> UART1 (GPS)
 - SERIAL4 -> UART4 (GPS2, Telem4/I2C)
 - SERIAL5 -> unused
 - SERIAL6 -> UART7 (debug port)
 - SERIAL7 -> USB2 (virtual port on same connector)

The Telem1 port has RTS/CTS pins, the other UARTs do not have RTS/CTS.

## Connectors

Unless noted otherwise all connectors are JST GH

### TELEM1 port

   <table border="1" class="docutils">
   <tbody>
   <tr>
   <th>Pin </th>
   <th>Signal </th>
   <th>Volt </th>
   </tr>
   <tr>
   <td>1 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>2 (blk)</td>
   <td>TX (OUT)</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>3 (blk)</td>
   <td>RX (IN)</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>4 (blk)</td>
   <td>CTS</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>5 (blk)</td>
   <td>RTS</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>6 (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   </tbody>
   </table>


### GPS1 port

   <table border="1" class="docutils">
   <tbody>
   <tr>
   <th>Pin</th>
   <th>Signal</th>
   <th>Volt</th>
   </tr>
   <tr>
   <td>1 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>2 (blk)</td>
   <td>TX (OUT)</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>3 (blk)</td>
   <td>RX (IN)</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>4 (blk)</td>
   <td>SCL I2C1</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>5 (blk)</td>
   <td>SDA I2C1</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>6 (blk)</td>
   <td>Button</td>
   <td>GND</td>
   </tr>
   <tr>
   <td>7 (blk)</td>
   <td>button LED</td>
   <td>GND</td>
   </tr>
   <tr>
   <td>8 (blk)</td>
   <td>3.3V</td>
   <td>3.3</td>
   </tr>
   <tr>
   <td>9 (blk)</td>
   <td>buzzer</td>
   <td>GND</td>
   </tr>
   <tr>
   <td> (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   </tbody>
   </table>



### GPS2, Telem4/I2C port

   <table border="1" class="docutils">
   <tbody>
   <tr>
   <th>Pin</th>
   <th>Signal</th>
   <th>Volt</th>
   </tr>
   <tr>
   <td>1 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>2 (blk)</td>
   <td>TX (OUT)</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>3 (blk)</td>
   <td>RX (IN)</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>4 (blk)</td>
   <td>SCL I2C2</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>5 (blk)</td>
   <td>SDA I2C2</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>6 (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   </tbody>
   </table>

### I2C

   <table border="1" class="docutils">
   <tbody>
   <tr>
   <th>Pin</th>
   <th>Signal</th>
   <th>Volt</th>
   </tr>
   <tr>
   <td>1 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>2 (blk)</td>
   <td>SCL</td>
   <td>+3.3 (pullups)</td>
   </tr>
   <tr>
   <td>3 (blk)</td>
   <td>SDA</td>
   <td>+3.3 (pullups)</td>
   </tr>
   <tr>
   <td>4 (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   </tbody>
   </table>


### CAN1

   <table border="1" class="docutils">
   <tbody>
   <tr>
   <th>Pin</th>
   <th>Signal</th>
   <th>Volt</th>
   </tr>
   <tr>
   <td>1 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>2 (blk)</td>
   <td>CAN_H</td>
   <td>+12V</td>
   </tr>
   <tr>
   <td>3 (blk)</td>
   <td>CAN_L</td>
   <td>+12V</td>
   </tr>
   <tr>
   <td>4 (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   </tbody>
   </table>


### POWER1

   <table border="1" class="docutils">
   <tbody>
   <tr>
   <th>Pin</th>
   <th>Signal</th>
   <th>Volt</th>
   </tr>
   <tr>
   <td>1 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>2 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>3 (blk)</td>
   <td>CURRENT</td>
   <td>up to +3.3V</td>
   </tr>
   <tr>
   <td>4 (blk)</td>
   <td>VOLTAGE</td>
   <td>up to +3.3V</td>
   </tr>
   <td>5 (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   <td>6 (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   </tbody>
   </table>


### USB

   <table border="1" class="docutils">
   <tbody>
   <tr>
   <th>Pin </th>
   <th>Signal </th>
   <th>Volt </th>
   </tr>
   <tr>
   <td>1 (red)</td>
   <td>VCC</td>
   <td>+5V</td>
   </tr>
   <tr>
   <td>2 (blk)</td>
   <td>D_minus</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>3 (blk)</td>
   <td>D_plus</td>
   <td>+3.3V</td>
   </tr>
   <tr>
   <td>4 (blk)</td>
   <td>GND</td>
   <td>GND</td>
   </tr>
   </tbody>
   </table>

## RC Input
 
RC input is configured on the RCIN pin, at one end of the servo rail,
marked RCIN in the above diagram. This pin supports all RC
protocols.

## PWM Output

The SIYI N7 supports up to 13 PWM outputs. First first 8 outputs
(labelled "MAIN") are controlled by a dedicated STM32F103 IO
controller. These 8 outputs support all PWM output formats, but not
DShot.

The remaining 5 outputs (labelled AUX1 to AUX5) are the "auxiliary"
outputs. These are directly attached to the STM32H743 and support all
PWM protocols as well as DShot.

All 13 PWM outputs have GND on the top row, 5V on the middle row and
signal on the bottom row.

The 8 main PWM outputs are in 3 groups:

 - PWM 1 and 2 in group1
 - PWM 3 and 4 in group2
 - PWM 5, 6, 7 and 8 in group3

The 4 auxiliary PWM outputs are in 2 groups:

 - PWM 1, 2, 3 and 4 in group4
 - PWM 5 in group5

Channels within the same group need to use the same output rate. If
any channel in a group uses DShot then all channels in the group need
to use DShot.

## Battery Monitoring

The board has a dedicated power monitor ports on a 6 pin
connector. The correct battery setting parameters are dependent on
the type of power brick which is connected.

## Compass

The SIYI N7 has one builtin IST8310 compass.

## GPIOs

The 5 AUX PWM ports can be used as GPIOs (relays, buttons, RPM etc).

The numbering of the GPIOs for PIN variables in ArduPilot is:

 - PWM1 50
 - PWM2 51
 - PWM3 52
 - PWM4 53
 - PWM5 54

## Analog inputs

The SIYI N7 has 7 analog inputs

 - ADC Pin16 -> Battery Voltage
 - ADC Pin17 -> Battery Current Sensor

## IMU Heater

The IMU heater in the SIYI N7 can be controlled with the
BRD_HEAT_TARG parameter, which is in degrees C.

## Loading Firmware

The board comes pre-installed with an ArduPilot compatible bootloader,
allowing the loading of *.apj firmware files with any ArduPilot
compatible ground station.