驱动开发

PX4 device drivers are based on the Device framework.

创建驱动程序

PX4 almost exclusively consumes data from uORB. 常见外设类型的驱动程序必须发布正确的 uORB 消息（例如: 陀螺仪、加速度计、压力传感器等）。

The best approach for creating a new driver is to start with a similar driver as a template (see src/drivers).

INFO

More detailed information about working with specific I/O buses and sensors may be available in Sensor and Actuator Buses section.

INFO

Publishing the correct uORB topics is the only pattern that drivers must follow.

核心架构

PX4 is a reactive system and uses uORB publish/subscribe to transport messages. File handles are not required or used for the core operation of the system. Two main APIs are used:

• Publish / subscribe 系统具有文件、网络或共享内存后端，具体取决于系统 PX4 运行。
• The global device registry, which can be used to enumerate devices and get/set their configuration. This can be as simple as a linked list or map to the file system. 这可以像链接列表或映射到文件系统一样简单。

设备ID

For the example of three magnetometers on a system, use the flight log (.px4log) to dump the parameters. The three parameters encode the sensor IDs and MAG_PRIME identifies which magnetometer is selected as the primary sensor. Each MAGx_ID is a 24bit number and should be padded left with zeros for manual decoding. 这三个参数解码传感器的 ID， 并且 MAG_PRIME 区分那个磁力计作为主传感器。

The order of sensors (e.g. if there is a /dev/mag0 and an alternate /dev/mag1) does not determine priority - the priority is instead stored as part of the published uORB topic.

解码示例

This is the internal HMC5983 connected via SPI, bus 1, slave select slot 5. It will show up in the log file as IMU1.MagX. The three parameters encode the sensor IDs and MAG_PRIME identifies which magnetometer is selected as the primary sensor. Each MAGx_ID is a 24bit number and should be padded left with zeros for manual decoding.

CAL_MAG0_ID = 73225.0
CAL_MAG1_ID = 66826.0
CAL_MAG2_ID = 263178.0
CAL_MAG_PRIME = 73225.0

This is the external HMC5983 connected via I2C, bus 1 at address 0x1E: It will show up in the log file as IMU.MagX.

# device ID 73225 in 24-bit binary:
00000001  00011110  00001 001

# decodes to:
HMC5883   0x1E    bus 1 I2C

根据此格式，设备 ID 是一个24bit 数字。 It will show up in the log file as IMU1.MagX.

# device ID 66826 in 24-bit binary:
00000001  00000101  00001 010

# decodes to:
HMC5883   dev 5   bus 1 SPI

And this is the internal MPU9250 magnetometer connected via SPI, bus 1, slave select slot 4. It will show up in the log file as IMU2.MagX.

# device ID 263178 in 24-bit binary:
00000100  00000100  00001 010

#decodes to:
MPU9250   dev 4   bus 1 SPI

设备 ID 编码

The device ID is a 24bit number according to this format. Note that the first fields are the least significant bits in the decoding example above.

struct DeviceStructure {
  enum DeviceBusType bus_type : 3;
  uint8_t bus: 5;    // which instance of the bus type
  uint8_t address;   // address on the bus (eg. I2C address)
  uint8_t devtype;   // device class specific device type
};

The bus_type is decoded according to:

enum DeviceBusType {
  DeviceBusType_UNKNOWN = 0,
  DeviceBusType_I2C     = 1,
  DeviceBusType_SPI     = 2,
  DeviceBusType_UAVCAN  = 3,
};

and devtype is decoded according to:

#define DRV_MAG_DEVTYPE_HMC5883  0x01
#define DRV_MAG_DEVTYPE_LSM303D  0x02
#define DRV_MAG_DEVTYPE_ACCELSIM 0x03
#define DRV_MAG_DEVTYPE_MPU9250  0x04
#define DRV_ACC_DEVTYPE_LSM303D  0x11
#define DRV_ACC_DEVTYPE_BMA180   0x12
#define DRV_ACC_DEVTYPE_MPU6000  0x13
#define DRV_ACC_DEVTYPE_ACCELSIM 0x14
#define DRV_ACC_DEVTYPE_GYROSIM  0x15
#define DRV_ACC_DEVTYPE_MPU9250  0x16
#define DRV_GYR_DEVTYPE_MPU6000  0x21
#define DRV_GYR_DEVTYPE_L3GD20   0x22
#define DRV_GYR_DEVTYPE_GYROSIM  0x23
#define DRV_GYR_DEVTYPE_MPU9250  0x24
#define DRV_RNG_DEVTYPE_MB12XX   0x31
#define DRV_RNG_DEVTYPE_LL40LS   0x32

调试

For general debugging topics see: Debugging/Logging.

使用操纵杆

Drivers (and other modules) output minimally verbose logs strings by default (e.g. for PX4_DEBUG, PX4_WARN, PX4_ERR, etc.).

Log verbosity is defined at build time using the RELEASE_BUILD (default), DEBUG_BUILD (verbose) or TRACE_BUILD (extremely verbose) macros.

Change the logging level using COMPILE_FLAGS in the driver px4_add_module function (CMakeLists.txt). The code fragment below shows the required change to enable DEBUG_BUILD level debugging for a single module or driver.

px4_add_module(
	MODULE templates__module
	MAIN module

	COMPILE_FLAGS
		-DDEBUG_BUILD

	SRCS
		module.cpp
	DEPENDS
		modules__uORB
	)

TIP

Verbose logging can also be enabled on a per-file basis, by adding #define DEBUG_BUILD at the very top of a .cpp file (before any includes).