I2C Bus (Development Overview)
I2C 是一种分组交换串行通信协议，允许多个主设备连接到多个从属设备，每个连接只需使用2根电线。 它用于在短距离、板内通信中将低速外设 IC 连接到处理器和微控制器。
Pixhawk/PX4 支持：
- Connecting off board components that require higher data rates than provided by a strict serial UART, such as rangefinders.
- 与仅支持 I2C 的外围设备兼容。
- 允许多个设备连接到单个总线（有效保护端口）。 例如，LED、指南针、测距仪等。
The page Hardware > I2C Peripherals contains information about how to use (rather than integrate) I2C peripherals and solve common setup problems.
IMUs (accelerometers/gyroscopes) should not be attached via I2C (typically the SPI bus is used). The bus is not fast enough even with a single device attached to allow vibration filtering (for instance), and the performance degrades further with every additional device on the bus.
集成 I2C 设备
Drivers should #include <drivers/device/i2c.h> and then provide an implementation of the abstract base class I2C defined in I2C.hpp for the target hardware (i.e. for NuttX here).
A small number of drivers will also need to include headers for their type of device (drv_*.h) in /src/drivers/ - e.g. drv_led.h.
To include a driver in firmware you must add the driver to the board-specific cmake file that corresponds to the target you want to build for. You can do this for a single driver:
drivers/sf1xxYou can also include all drivers of a particular type.
CONFIG_COMMON_DISTANCE_SENSOR=yTIP
For example, you can see/search for CONFIG_DRIVERS_DISTANCE_SENSOR_LIGHTWARE_LASER_I2C in the px4_fmu-v4_default configuration.
I2C 驱动程序示例
To find I2C driver examples, search for i2c.h in /src/drivers/.
Just a few examples are:
- drivers/distance_sensor/lightware_laser_i2c - I2C driver for Lightware SF1XX LIDAR.
- drivers/distance_sensor/lightware_laser_serial - Serial driver for Lightware SF1XX LIDAR.
- drivers/ms5611 - I2C Driver for the MS5611 and MS6507 barometric pressure sensor connected via I2C (or SPI).