多旋翼无人机
我们采用的开源无人机飞控硬件是pixhawk，版本号为2.4.8。相对来说这是一个比较稳定的版本，经过实际的飞行测试，效果比较理想。
接下来我们就来简单介绍一下pixhawk硬件的相关内容。
pixhawk是一套集成了传感器、输入输出功能及嵌入式处理芯片的电路板。它主要由两部分构成：PX4FMU和PX4IO。
一、FMU
FMU中集成了STM32F427处理芯片、MPU6050三轴加速计和三轴陀螺仪、MS5611气压计、LSM303D加速度计和磁罗盘。以及丰富的总线接口，4路串口、SPI、I2C、ADC接口等等。FMU采用的单片机STM32F427，主要负责对传感器的数据进行采集并进行姿态和位置解算，并通过经典PID控制程序输出控制量到IO程序中，生成飞行控制量，进而控制飞机的飞行。
二、IO
IO电路板中采用的芯片为SMT32F103C8，主要负责的是输入和输出。输入部分指以SBUS协议的遥控器串口信号。在遥控器一节中我们已经讲述SBUS协议通常是以反向电平接入的，所以在电路设计上需要接入一个高低电平反向器。这个细节pixhawk已经为我们处理好了。我们不需要再额外加入反向器。输出部分共有13个PWM信号接口，其中M1-M8为主动力通道，接主动力电调电机，而A1-A5为可选外设的辅助通道。可以接一些其它设备，例如云台和相机等。
三、接口介绍
1、双数传TELEM1, TELEM2 接口：
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | TX (OUT) | +3.3V |
| 3 (blk) | RX (IN) | +3.3V |
| 4 (blk) | CTS (IN) | +3.3V |
| 5 (blk) | RTS (OUT) | +3.3V |
| 6 (blk) | GND | GND |
2、全球定位系统 GPS接口：
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | TX (OUT) | +3.3V |
| 3 (blk) | RX (IN) | +3.3V |
| 4 (blk) | CAN2 TX | +3.3V |
| 5 (blk) | CAN2 RX | +3.3V |
| 6 (blk) | GND | GND |
3、双终端串口SERIAL 4/5 port接口：
| Pixhawk | FTDI | ||
|---|---|---|---|
| 1 | +5V (red) | N/C | |
| 2 | S4 Tx | N/C | |
| 3 | S4 Rx | N/C | |
| 4 | S5 Tx | FTDI RX | |
| 5 | S5 Rx | FTDI TX | |
| 6 | GND | FTDI GND |
4、ADC 6.6V电压采集接口：
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | ADC IN | up to +6.6V |
| 3 (blk) | GND | GND |
5、ADC 3.3V电压采集接口：
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | ADC IN | up to +3.3V |
| 3 (blk) | GND | GND |
| 4 (blk) | ADC IN | up to +3.3V |
| 5 (blk) | GND | GND |
6、I2C接口
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | SCL | +3.3 (pullups) |
| 3 (blk) | SDA | +3.3 (pullups) |
| 4 (blk) | GND | GND |
7、CAN总线接口
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | CAN_H | +12V |
| 3 (blk) | CAN_L | +12V |
| 4 (blk) | GND | GND |
8、SPI总线接口：
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | SPI_EXT_SCK | +3.3 |
| 3 (blk) | SPI_EXT_MISO | +3.3 |
| 4 (blk) | SPI_EXT_MOSI | +3.3 |
| 5 (blk) | !SPI_EXT_NSS | +3.3 |
| 6 (blk) | !GPIO_EXT | +3.3 |
| 7 (blk) | GND | GND |
9、电源POWER接口：
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +5V |
| 2 (blk) | VCC | +5V |
| 3 (blk) | CURRENT | +3.3V |
| 4 (blk) | VOLTAGE | +3.3V |
| 5 (blk) | GND | GND |
| 6 (blk) | GND | GND |
10、安全开关SWITCH接口：
| Pin | Signal | Volt |
|---|---|---|
| 1 (red) | VCC | +3.3V |
| 2 (blk) | !IO_LED_SAFETY | GND |
| 3 (blk) | SAFETY | GND |
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