在USB示波器上使用Linux

Digilent’s New Analog Discovery Pro ‘Opens’ It Up

随着设计要求变得越来越复杂，世界各地的工程师被要求缩短设计周期时间并增加产出。可以研究，验证和测试的灵活测试设备是工程师可以加快此过程的方式之一。这种需求与Covid-19的工程迅速适应，这对测试和测量公司施加了压力，以便在半导体行业面临工厂关闭的同时提供灵活的便携式解决方案。接下来几个月接听电话是ADP3450, the first in the line of Analog Discovery Pro products, which in addition to providing a reliable instrument when connected to WaveForms, also introduces an entirely new way to interact with a portable device of its kind, Linux Mode.

Linux Mode提供了一个设备操作系统，当与Woveforms SDK结合使用时，它是各种自定义测试和应用程序的灵活跳跃点。作为设备每个操作模式的经典演示，我对经典的LED眨眼示例进行了两个测试和测量，例如ADC的自动测试，以及非常简单的功率测量演示。

测试对数字转换器的类似物

The first demonstration is an automated test of an analog to digital converter, which I have chosen in the form factor of aPmod为简单起见。使用波形SDK来完成测试的自动化以控制AWG，以使用模拟信号刺激模块并控制示波器以捕获和解码SPI交易。

The ADP3450 defaults into Standard Mode, which allows you to connect via USB or ethernet to a computer running WaveForms to take quick measurements as you would on any standard USB Oscilloscope or Logic Analyzer. Booting into Linux Mode is as simple as changing the boot Mode setting and clicking apply:

Once booted, a terminal application can be used to connect to the serial port of the device. For this example, Python is used to write the test, although several other languages can be used as well to write the script.

该脚本完整地通过SPI配置PMODAD5，并在用于设置AWG的DC信号的电压列表上迭代。然后，它通过SPI发布读取命令，记录结果，并继续到下一个电压，直到没有剩下为止。测试完成后，结果将显示在终端上。

一旦正确安装脚本，就可以运行，输出如下所示：

在实际系统中，示波器可以读取实际的模拟数据，比较结果并根据设定标准发布或失败。

如果对脚本和波形的开发感兴趣，SDK功能有完整地写出此自动测试的详细信息。

值得注意的是，Linux模式和标准模式是独立的，并且每个模式都有自己的恢复方法。这样，如果您在Linux模式下变得过于富有创造力并且出现问题，则标准模式将继续按预期运行，并且可以使用Linux恢复模式在最早的方便时使用Linux Recovery模式来重新刷新设备的部分。

下一个演示使用传统的USB仪器模式，标准模式。要切换模式，只需选择引导模式并重新启动。

A common measurement in the design process is power, but inherently most oscilloscopes measure voltage. With some basic math functions power measurements can be calculated in real time. To demonstrate this, a basic RC circuit will be used.

For this test we enabled three of the four available oscilloscope channels in WaveForms:

Then used the AWG to stimulate our basic circuit:

Back in the Oscilloscope, the voltage drop across the sensing resistor (Ch 1), the voltage drop across the entire circuit (Ch 2), and the voltage drop across the two resistors (Ch 3), can be seen.

Math channels can be added for each channel to calculate power for each component using the various node voltages captured by the oscilloscope and the known resistor values. First adding a math channel for the power across resistor one:

Then for the following resistor and capacitor. For clarity’s sake the oscilloscope channels have been hidden:

对于每个数学渠道，每个功率测量的平均值都可以提供更清晰的信息：

Since these measurements and calculations are taken live with an oscilloscope further exploration can be achieved by adjusting the stimulus of the circuit.

有关更多详细信息，有全文这个例子也是如此。

This example focused primarily on the Oscilloscope and Waveform generator instruments, but a multitude of calculated tests can be accomplished using the 12 instruments on the device. Including frequency domain calculations with the spectrum analyzer and bode plot in the network analyzer, impedance analysis, and stimulus, capture and decoding of digital signals in the digital instruments. Outside of the existence of these instruments the ADP3450 offers much more that should be mentioned.

The full set ofspecifications可以在这里找到。

作为功​​能的摘要，设备本身或通过波形进行的测量可以利用通过以太网进行更快的数据流，在设备存储中以捕获数百万个样本的缓冲区，14位分辨率和集成的BNC连接器，以及到达。大大增加了可捕获的信号，可以使用不同的样品模式来捕获最高0.5GS/s的重复信号。