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OpenIPC开源FPV之Adaptive-Link地面站代码解析

news 2024/12/17 10:59:22

OpenIPC开源FPV之Adaptive-Link地面站代码解析

1. 源由
2. 框架代码
3. 软件配置
- 3.1 默认配置
- 3.2 加载配置
- 3.3 更新配置
4. 通信例程
- 4.1 TCP报文解析
- 4.2 UDP报文发送
5. 特殊指令
- 5.1 request_keyframe
- 5.2 drop_gop
- 5.3 resume_adaptive
- 5.4 pause_adaptive
6. 总结
7. 参考资料

1. 源由

在《OpenIPC开源FPV之Adaptive-Link工程解析》中，已经有了整个工程的大体概念，接下来再对代码进行逐步分析。

在之前对天空端代码进行了研读，接下来对地面端的代码进行分析：alink_gs.py

2. 框架代码

配置：“/etc/adaptive_link.conf”
wfb-cli：127.0.0.1:8003
UDP: 10.5.0.10:9999

__main__├──> load_config(args.config)  // --config "/etc/adaptive_link.conf"└──> connect_and_receive_msgpack()

注：connect_and_receive_msgpack 建立TCP和UDP通信管道。

3. 软件配置

3.1 默认配置

VERSION = "0.1.1"# Global variables
results = []
link_health_score_rssi = 1000  # Default score before calculation for RSSI
link_health_score_snr = 1000  # Default score before calculation for SNR
recovered_packets = 0  # To store the number of recovered packets (FEC)
lost_packets = 0  # To store the number of lost packets
best_antennas_rssi = [-105, -105, -105, -105]  # Default values for best antennas RSSI if less than 4
best_antennas_snr = [-105, -105, -105, -105]  # Default values for best antennas SNR if less than 4
config = None  # Configuration file object
udp_socket = None  # To store the UDP socket globally
udp_ip = None  # To store the UDP IP globally
udp_port = None  # To store the UDP port globally
previous_link_health_score_rssi = None
previous_link_health_score_snr = None# Default config values
DEFAULT_CONFIG = {'Settings': {'version': VERSION,  # Current version of the script'message_interval': '100',  # Time between sending messages (milliseconds)'use_best_rssi': 'True',  # Option to pick best available RSSI for link health score'min_rssi': '-85',  # Min RSSI range for link health'max_rssi': '-50',  # Max RSSI range for link health'min_snr': '12',  # Min SNR range for link health'max_snr': '28',  # Max SNR range for link health'host': '127.0.0.1',  # Host address to connect to'port': '8003',  # Port to connect to'udp_ip': '10.5.0.10',  # UDP IP to send link health data'udp_port': '9999',  # UDP port to send link health data'retry_interval': '1',  # Time in seconds to wait before retrying TCP connection on failure},'Descriptions': {'version': 'Version of the script','message_interval': 'Time between sending UDP messages in milliseconds','use_best_rssi': 'Use True to pick the best available RSSI for health score, or False for average RSSI','min_rssi': 'Minimum RSSI value used for link health calculation','max_rssi': 'Maximum RSSI value used for link health calculation','min_snr': 'Minimum SNR value used for link health calculation','max_snr': 'Maximum SNR value used for link health calculation','host': 'Host address to connect to for the TCP connection','port': 'Port to connect to for the TCP connection','udp_ip': 'UDP IP to send the link health data','udp_port': 'UDP port to send the link health data','retry_interval': 'Time in seconds to wait before retrying TCP connection on failure'}
}

3.2 加载配置

配置通过"/etc/adaptive_link.conf"文件传入，若没有该文件，系统默认生成一份。

load_config(config_file='config.ini')├──> Check if config file exists│     ├──> File does not exist│     │     ├──> Print "Config file not found, creating..."│     │     ├──> Load default values into config (DEFAULT_CONFIG)│     │     └──> Write default config to file│     └──> File exists│           └──> Read existing config file├──> Check version mismatch│     ├──> Config version != VERSION│     │     ├──> Print "Updating version in config file..."│     │     ├──> Update config['Settings']['version'] to VERSION│     │     └──> Call update_version_history(config_file)│     └──> Config version == VERSION (do nothing)├──> Ensure all default fields are present│     ├──> Iterate through DEFAULT_CONFIG sections and keys│     │     ├──> Section missing → Add section to config│     │     ├──> Key missing in section → Add key to config│     │     └──> Mark config as updated├──> Save updated config (if needed)│     └──> Write updated config to file└──> Return (config is now fully loaded and updated)

3.3 更新配置

若无该配置文件，通过该命令直接生成一个默认配置文件。

注：配置文件升级更新，暂时无该功能。

def update_version_history(config_file):"""Updates the version history in the configuration file."""if 'Version History' not in config:config['Version History'] = {}# Add the current version with a timestamptimestamp = time.strftime('%Y-%m-%d %H:%M:%S', time.gmtime())config['Version History'][VERSION] = f"Version {VERSION} updated on {timestamp}"# Write the updated config to filewith open(config_file, 'w') as f:config.write(f)

4. 通信例程

UDP: 10.5.0.10:9999
TCP: 127.0.0.1:8003

connect_and_receive_msgpack()├──> Initialize UDP socket and thread  // 10.5.0.10:9999│     ├──> Create global UDP socket (udp_socket)│     └──> Start generate_package() in a separate thread├──> Infinite loop to handle TCP connection and data // 127.0.0.1:8003│     ├──> Try to connect to the server│     │     ├──> Create TCP socket (client_socket)│     │     ├──> Connect to (host, port)│     │     └──> Read data from server in a loop│     │           ├──> Read 4-byte length prefix│     │           ├──> Extract message length (msg_length)│     │           ├──> Read actual message data of length msg_length│     │           │     ├──> Append chunks of data until full message is received│     │           │     └──> Handle incomplete data or connection issues│     │           └──> Unpack and process MessagePack data│     │                 ├──> Append unpacked data to results array│     │                 ├──> Handle "video rx" message│     │                 │     └──> Update link health metrics (RSSI, SNR, etc.)│     │                 └──> Handle unpack errors│     └──> Handle connection issues│           └──> Print error and retry connection after retry_interval seconds└──> Return (loop runs indefinitely)

4.1 TCP报文解析

通过wfb-cli的TCP 8003端口获取本地RF信息数据。

calculate_link_health(video_rx)
├──> Global Variables Declaration
├──> Configuration Settings (Extract from `config`)
│   ├──> message_interval
│   ├──> use_best_rssi
│   ├──> min_rssi, max_rssi
│   └──> min_snr, max_snr
├──> Packets Data Retrieval (from `video_rx`)
│   ├──> fec_rec → recovered_packets
│   ├──> lost → lost_packets
│   └──> Special Messages Logic
│       ├──> request_keyframe()
│       └──> (Optional) drop_gop()
├──> Antenna Statistics Processing
│   ├──> Extract RSSI/SNR per antenna
│   └──> Fallback Logic (Default Values)
├──> Best Antennas Selection
│   ├──> Sort `rssi_values` and `snr_values`
│   └──> Pad with `-105` if fewer than 4 antennas
├──> Link Health Score Calculation
│   ├──> RSSI Health Score
│   │   ├──> rssi_to_use (Best vs Average)
│   │   └──> Interpolation Logic
│   ├──> SNR Health Score
│   │   ├──> avg_best_snr (Best vs Average)
│   │   └──> Interpolation Logic
│   └──> (Optional) Hysteresis Logic
├──> Rounding and Logging
└──> Return Scores (RSSI, SNR)

4.2 UDP报文发送

定期将本地最新全局变量组包

def generate_package():"""Generate, at interval, string with all the variables"""message_interval = int(config['Settings']['message_interval']) / 1000  # Convert to secondswhile True:timestamp = int(time.time())  # Get epoch time in seconds since 1970# Include best antennas in the messagemessage = f"{timestamp}:{link_health_score_rssi}:{link_health_score_snr}:{recovered_packets}:{lost_packets}:{best_antennas_rssi[0]}:{best_antennas_rssi[1]}:{best_antennas_rssi[2]}:{best_antennas_rssi[3]}"# Pass the message to send_udp functionsend_udp(message)time.sleep(message_interval)  # Send at the specified interval

通过UDP tunnel管道发送到天空端

def send_udp(message):"""Adds message length to the start and sends message on provided port"""if verbose_mode:print("send_udp function has started")  # Debug statement to confirm function start# Prepend the size of the message as a 4-byte unsigned integermessage_bytes = message.encode('utf-8')message_size = struct.pack('!I', len(message_bytes))  # Use network byte order (big-endian)# Full message with size prefixfull_message = message_size + message_bytesif verbose_mode:print("Preparing UDP message to be sent")  # Debug statement# Send the messagetry:udp_socket.sendto(full_message, (udp_ip, udp_port))if verbose_mode:print(f"UDP Message Sent: {message} (size: {len(message_bytes)} bytes)")except Exception as e:if verbose_mode:print(f"Error sending UDP data: {e}")

5. 特殊指令

5.1 request_keyframe

def request_keyframe():"""Send a special message to request a keyframe"""special_message = "special:request_keyframe"num_attempts = 0  # Number of times to send the messagefor attempt in range(num_attempts):send_udp(special_message)  # Call send_udp to send the special messageif verbose_mode:print(f"Sent special message: {special_message}, attempt {attempt + 1}/{num_attempts}")time.sleep(0.1)  # Wait before the next attempt

5.2 drop_gop

def drop_gop():"""Send a special message to drop the gop"""special_message = "special:drop_gop"num_attempts = 0  # Number of times to send the messagefor attempt in range(num_attempts):send_udp(special_message)  # Call send_udp to send the special messageif verbose_mode:print(f"Sent special message: {special_message}, attempt {attempt + 1}/{num_attempts}")time.sleep(0.1)  # Wait before the next attempt