源码：drivers/telemetry/frsky_telemetry
FrSky 数传支持， FrSky Telemetry support. Auto-detects D or S.PORT protocol.
frsky_telemetry <command> [arguments...]
frsky_telemetry <command> [arguments...]
Commands:
start
[-d <val>] Select Serial Device
values: <file:dev>, default: /dev/ttyS6
[-t <val>] Scanning timeout [s] (default: no timeout)
default: 0
[-m <val>] Select protocol (default: auto-detect)
values: sport|sport_single|dtype, default: auto
stop
status
源码： modules/mavlink
此模块实现了 MAVLink 协议，该协议可在串口或 UDP 网络上使用。 This module implements the MAVLink protocol, which can be used on a Serial link or UDP network connection. It communicates with the system via uORB: some messages are directly handled in the module (eg. mission protocol), others are published via uORB (eg. vehicle_command).
流（Stream）被用来以特定速率发送周期性的消息，例如飞机姿态信息。 Streams are used to send periodic messages with a specific rate, such as the vehicle attitude. When starting the mavlink instance, a mode can be specified, which defines the set of enabled streams with their rates. For a running instance, streams can be configured via mavlink stream command. 对于一个正在运行的实例而言，可以使用 mavlink stream 命令来配置流。
可以存在多个该模块的实例，每个实例连接到一个串口设备或者网络端口。
命令的具体实现使用了两个线程，分别为数据发送线程和接收线程。 发送线程以一个固定的速率运行，并会在组合带宽（combined bandwidth）高于设定速率(-r)，或者物理链路出现饱和的情况下动态降低信息流的发送速率。 可使用 mavlink status 命令检查是否发生降速，如果 rate mult 小于 1 则发生了降速。
Careful: some of the data is accessed and modified from both threads, so when changing code or extend the functionality, this needs to be take into account, in order to avoid race conditions and corrupt data.
在 ttyS1 串口启动 mavlink ，并设定波特率为 921600、最大发送速率为 80kB/s：
mavlink start -d /dev/ttyS1 -b 921600 -m onboard -r 80000
在 UDP 端口 14556 启动 mavlink 并启用 50Hz 的 HIGHRES_IMU 消息：
mavlink start -u 14556 -r 1000000
mavlink stream -u 14556 -s HIGHRES_IMU -r 50
mavlink <command> [arguments...]
mavlink <command> [arguments...]
Commands:
start Start a new instance
[-d <val>] Select Serial Device
values: <file:dev>, default: /dev/ttyS1
[-b <val>] Baudrate (can also be p:<param_name>)
default: 57600
[-r <val>] Maximum sending data rate in B/s (if 0, use baudrate / 20)
default: 0
[-u <val>] Select UDP Network Port (local)
default: 14556
[-o <val>] Select UDP Network Port (remote)
default: 14550
[-t <val>] Partner IP (broadcasting can be enabled via MAV_BROADCAST
param)
default: 127.0.0.1
[-m <val>] Mode: sets default streams and rates
values: custom|camera|onboard|osd|magic|config|iridium|minimal,
default: normal
[-n <val>] wifi/ethernet interface name
values: <interface_name>
[-c <val>] Multicast address (multicasting can be enabled via
MAV_BROADCAST param)
values: Multicast address in the range
[239.0.0.0,239.255.255.255]
[-f] Enable message forwarding to other Mavlink instances
[-w] Wait to send, until first message received
[-x] Enable FTP
[-z] Force flow control always on
stop-all Stop all instances
status Print status for all instances
[streams] Print all enabled streams
stream Configure the sending rate of a stream for a running instance
[-u <val>] Select Mavlink instance via local Network Port
default: 0
[-d <val>] Select Mavlink instance via Serial Device
values: <file:dev>
-s <val> Mavlink stream to configure
-r <val> Rate in Hz (0 = turn off, -1 = set to default)
boot_complete Enable sending of messages. (Must be) called as last step in
startup script. (必须) 作为启动脚本的最后一步被调用。
源码：modules/micrortps_bridge/micrortps_client
micrortps_client <command> [arguments...]
micrortps_client <command> [arguments...]
Commands:
start
[-t <val>] Transport protocol
values: UART|UDP, default: UART
[-d <val>] Select Serial Device
values: <file:dev>, default: /dev/ttyACM0
[-b <val>] Baudrate (can also be p:<param_name>)
default: 460800
[-p <val>] Poll timeout for UART in ms
default: 1
[-u <val>] Interval in ms to limit the update rate of all sent topics
(0=unlimited)
default: 0
[-l <val>] Limit number of iterations until the program exits
(-1=infinite)
default: 10000
[-w <val>] Time in ms for which each iteration sleeps
default: 1
[-r <val>] Select UDP Network Port for receiving (local)
default: 2019
[-s <val>] Select UDP Network Port for sending (remote)
default: 2020
stop
status
源码：modules/uORB
uORB 是各模块之间进行通讯的基于 发布-订阅 机制的内部消息传递系统。
uORB 模块通常作为第一个模块启动，并且绝大多数其它模块均依赖于它，
No thread or work queue is needed, the module start only makes sure to initialize the shared global state. Communication is done via shared memory. The implementation is asynchronous and lock-free, ie. a publisher does not wait for a subscriber and vice versa. This is achieved by having a separate buffer between a publisher and a subscriber. 通信是通过共享内存（shared memory）完成的。 The implementation is asynchronous and lock-free, ie. a publisher does not wait for a subscriber and vice versa. 这一特性是通过在发布者和订阅者之间建立单独的缓冲区来实现的。
我们对代码以最大限度地减少内存占用和交换消息的延迟为目标进行了优化。
该接口基于文件描述符（file descriptor）实现：它在内部使用 read、write 和 ioctl。 The interface is based on file descriptors: internally it uses read, write and ioctl. Except for the publications, which use orb_advert_t handles, so that they can be used from interrupts as well (on NuttX).
Messages are defined in the /msg directory. They are converted into C/C++ code at build-time. 在构建时它们会被转化为 C/C++ 代码。
If compiled with ORB_USE_PUBLISHER_RULES, a file with uORB publication rules can be used to configure which modules are allowed to publish which topics. This is used for system-wide replay. 这可以用于全系统范围的回放。
监控主题发布速率。 Monitor topic publication rates. Besides top, this is an important command for general system inspection:
uorb top
uorb <command> [arguments...]
uorb <command> [arguments...]
Commands:
start
status Print topic statistics
top Monitor topic publication rates
[-a] print all instead of only currently publishing topics
[<filter1> [<filter2>]] topic(s) to match (implies -a)