### 使用 Python 和 FTDI 操作 JTAG 并通过示波器捕获信号 要完成这一任务，需结合 PyFtdi 库来操作 JTAG 接口，并利用外部设备（如数字示波器）同步捕获发送的信号。以下是具体方法： #### 1. 配置 JTAG 环境 初始化 JTAG 引擎并与目标硬件建立连接。这一步骤已在之前的讨论中提及过[^9]。 ```python from pyftdi.jtag import JtagEngine def initialize_jtag(url='ftdi:///1', freq=3e6): jtag_engine = JtagEngine(trst=False, frequency=freq) try: jtag_engine.configure(url) except Exception as e: raise RuntimeError(f"Failed to configure JTAG engine: {str(e)}") from e if not jtag_engine.is_configured(): raise ValueError("The JTAG device could not be properly initialized.") return jtag_engine ``` #### 2. 编写发送指令函数 定义一个通用函数用于向目标设备发送特定的 TMS/TDI 数据流。该数据可以通过查阅目标芯片的技术手册获得。 ```python def send_jtag_instructions(jtag_engine, tms_bits, tdi_bits=None): """ Sends a sequence of bits over the JTAG interface using given TMS and optional TDI values. Args: jtag_engine (JtagEngine): Configured instance of the JtagEngine class. tms_bits (list[int]): List of integers representing TMS bit stream. tdi_bits (list[int], optional): List of integers representing TDI bit stream. Returns: list[int]: Response captured on TDO line during transmission. """ response = [] for i, tms_bit in enumerate(tms_bits): current_tdi = tdi_bits[i] if tdi_bits is not None and i < len(tdi_bits) else 0 resp = jtag_engine.write_tms([tms_bit], do=current_tdi) response.extend(resp) return response ``` #### 3. 同步示波器采集 为了能够观察到实际传输过程中的电信号变化情况，在执行上述命令的同时还需要启动另一条线程或者进程专门负责触发示波器开始记录指定通道上的电压波动状况。假设使用的是一款支持 SCPI 命令集并通过 LAN 进行管理的品牌型号，则可通过如下方式实现自动化控制目的: ```python import socket import time def setup_oscilloscope(ip_address="192.168.1.10", port=5025): sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.connect((ip_address, port)) return sock def trigger_capture(sock, timeout_seconds=5): cmd = "*IDN?\n" sock.sendall(cmd.encode()) identity = sock.recv(1024).decode().strip() print(f"Connected Oscilloscope: {identity}") # Configure acquisition settings before triggering capture config_cmds = [ ":ACQuire:TYPE NORMal\n", f":TIMebase:MAIN {timeout_seconds}s\n", ":CHANnel1:SCAle 1V\n", ":TRIGger:SOURce IMMEDIATE\n", ":DIGitize CHANnel1\n" ] for c in config_cmds: sock.sendall(c.encode()) start_time = time.time() while True: elapsed = time.time() - start_time if elapsed >= timeout_seconds: break status_cmd = ":STATus? TRIGger\n" sock.sendall(status_cmd.encode()) stat = sock.recv(1024).decode().strip() if '1' in stat: # Triggered event detected fetch_data_cmd = ":WAVeform:DATA? CHANnel1\n" sock.sendall(fetch_data_cmd.encode()) raw_waveform = sock.recv(1024 * 1024) # Adjust buffer size accordingly with open("captured_signal.bin", "wb") as wf_file: wf_file.write(raw_waveform) print("Signal successfully captured!") return ``` 以上脚本实现了基本的功能需求，但在真实场景应用之前可能还需针对具体的仪器品牌做进一步适配修改工作。 --- ###