Connecting PicoScope 4824A in MATLAB

Feb. 22, 2023

Introduction

Pico公司在Github中提供了在MATLAB中连接PicoScope产品的驱动以及相关的示例，不同系列的示波器的调用接口也不同。适配PicoScope 4824A的驱动见：PicoScope 4000 Series A API MATLAB Generic Instrument Driver - Github。这个驱动可以直接在MATLAB Add-Ons中直接下载。

image-20230222163859156

使用该Driver需要提前在MATLAB中安装：Instrument Control Toolbox，PicoScope Support Toolbox. 这两个工具箱同样可以在MATLAB Add-Ons中进行下载。

下载 PicoScope 4000 Series A API MATLAB Generic Instrument Driver 后，其文件夹中包含这些文件：

image-20230222164455771

在根文件中主要包含一个定义的类PS4000aConstants.m，一个函数文件ps4000aSetConfig.m和一个脚本文件PS4000aConfig.m，和一个MDD类型的文件picotech_ps4000a_generic.mdd。另外，还包含一个exmaples文件夹，提供了一些使用驱动的示例。


Examples

examples文件夹中包含了六个使用驱动的示例。其实现的功能和运行的结果分别如下所示。

注：在运行下面示例的时候，仅仅是将Pico采集卡与笔记本相连，各通道均没有连接传感器，收集到的信号都是噪声信号。

PS4000A_ID_Block_Adv_Trigger_PWQ_Example.m

Demonstrates how to call Instrument Driver functions in order to capture a block of data using advanced trigger functions with a pulse width qualifier.

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PS4000A_ID_Block_Example.m

Demonstrates how to call Instrument Driver functions in order to capture a block of data from a PicoScope 4000 Series oscilloscope.

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PS4000A_ID_Block_FFT_Example.m

Demonstrates how to call Instrument Driver functions in order to capture a block of data from a PicoScope 4000 Series oscilloscope. A Fast Fourier Transform (FFT) is then applied to the data collected on channel A.

pic1

PS4000A_ID_Rapid_Block_Plot3D_Example.m

Demonstrates how to call Instrument Driver functions in order to capture data in rapid block mode from a PicoScope 4000 Series oscilloscope.

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PS4000A_ID_Sig_Gen_Example.m

Demonstrates how to call Instrument Driver functions in order to control the signal generator output (where available) of a PicoScope 4000 Series oscilloscope.

这个示例需要使用到PicoScope背面的信号输出端口：

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代码的备注提到示波器的输出端口可以与另一个PicoScope相连，就可以在软件中显示相应波形：

For this example the ‘Gen’ output of the oscilloscope was connected to Channel A on another PicoScope oscilloscope running the PicoScope 6 software application. Images, where shown, depict output, or part of the output in the PicoScope 6 display.

但实际上，一个PicoScope的Gen端口可以直接与前面的采集端口直接相连。因此，通过一个BNC接线就可以将这个示例与其他的示例联合起来使用。

The various signal generator functions called in this script may be combined with the functions used in the various data acquisition examples in order to output a signal and acquire data. The functions to setup the signal generator should be called prior to the start of data collection.

PS4000A_ID_Streaming_Example.m

Demonstrates how to call functions in order to capture data in streaming mode from a PicoScope 4000 Series oscilloscope.

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在运行的过程中，会跳出一个弹框，询问是否实时显示streaming data：

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若选择是，则会在另一个窗口动态地绘制出信号变化的过程：

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Create a device object & Connect to the instrument

在所有的示例文件中，前两步都是固定的，分别是Create a device object 和 Connect to the instrument.

Create a device object

Load configuration information

在创建对象时，首先需要加载配置信息：设置路径并加载struct和enumeration信息。

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%% Load configuration information
% Setup paths and also load struct and enumeration information. Enumeration
% values are required for certain function calls.
[ps4000aStructs, ps4000aEnuminfo] = ps4000aSetConfig(); % DO NOT EDIT THIS LINE.

ps4000aSetConfig()函数就是前面提到的在根文件夹中定义的那个函数。该函数的作用是将prototype files文件加载到MATLAB的工作空间中，以供Instrument Driver picotech_ps4000a_generic.mdd获取信息。不同的平台导入的信息是不一样的。

This function allows the information from the prototype files to be loaded into the workspace that the picotech_ps4000a_generic.mdd Instrument Driver is accessed from.

Configures paths according to platforms and loads information from prototype files for PicoScope 4000 Series Oscilloscopes using the functions from the ps4000a/libps4000a shared library. The folder that this file is located in must be added to the MATLAB path.

路径和文件应该是保存在Pico所提供的SDK中：

Platform Specific Information:-

Microsoft Windows: Download the Software Development Kit installer from the Pico Technology Download software and manuals for oscilloscopes and data loggers page.

注释也特别提醒”DO NOT EDIT THIS LINE.”，只需要在连接设备前调用即可：

Run this script (ps4000aSetConfig.m) in the MATLAB environment prior to connecting to the device.

如果有特殊需要的话，用户可以修改ps4000aSetConfig.m文件：

This file (ps4000aSetConfig.m) can be edited to suit application requirements.

在执行完上面那行代码后，在工作空间中会出现两个结构体ps4000aEnuminfo和ps4000aStructs；这两个结构体里面同样嵌套着很多结构体，里面保存着大量的定义好的常量。

Check before connection

在创建device object ps4000aDeviceObj前，需要先检查Instrument session是否仍然处于open的状态，如果处于open的状态，则会弹出这样一个弹窗：

image-20230222193115369

如果选择Yes，则会先关闭session，然后再运行后面的代码；如果选择了No，则会调出脚本文件，不会再执行后面的代码。

在所有的示例文件中，在代码的最后都会断开并删除session：

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%% Disconnect device
% Disconnect device object from hardware.
disconnect(ps4000aDeviceObj);
delete(ps4000aDeviceObj);

因此，一般情况下不会弹出这个对话框。

这部分实现的代码是：

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% Check if an Instrument session using the device object 'ps4000aDeviceObj'
% is still open, and if so, disconnect if the User chooses 'Yes' when prompted.
if (exist('ps4000aDeviceObj', 'var') && ps4000aDeviceObj.isvalid && strcmp(ps4000aDeviceObj.status, 'open'))
    openDevice = questionDialog(['Device object ps4000aDeviceObj has an open connection. ' ...
        'Do you wish to close the connection and continue?'], ...
        'Device Object Connection Open');
    if (openDevice == PicoConstants.TRUE)
        % Close connection to device
        disconnect(ps4000aDeviceObj);
        delete(ps4000aDeviceObj);
    else
        % Exit script if User 
        return
    end
end

逻辑也比较清晰。

Create a device object

之后创建Device oject：

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% Create a device object. 
% The serial number can be specified as a second input parameter.
ps4000aDeviceObj = icdevice('picotech_ps4000a_generic.mdd', '');

icdevice函数是MATLAB Instrument Control Toolbox 的内置函数：icdevice - MathWorks. 参数'picotech_ps4000a_generic.mdd'就是一个instrument driver，同样定义在工具箱的根文件夹中。打开picotech_ps4000a_generic.mdd`文件，会弹出下面的页面：

image-20230222201027864

里面是关于Pico所定义的这个驱动的相关信息。

运行代码ps4000aDeviceObj = icdevice('picotech_ps4000a_generic.mdd', '');后，此时工作空间中多出了一个ps4000aDeviceObj的icdevice类的变量。双击该变量，则会弹出页面：

image-20230222201536141

在命令行中也会打印出一些关于Device object的说明信息：

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PicoScope 4000 Series (A API) MATLAB Instrument Driver

Copyright © 2014-2019 Pico Technology Ltd. All rights reserved.

   Instrument Device Object Using Driver : picotech_ps4000a_generic.mdd
 
   Instrument Information
      Type:               Oscilloscope
      Manufacturer:       Pico Technology Ltd.
      Model:              PicoScope 4000 Series (A API)
 
   Driver Information
      DriverType:         MATLAB generic
      DriverName:         picotech_ps4000a_generic.mdd
      DriverVersion:      1.2.16.10
 
   Communication State
      Status:             closed

Number of units found: 1

Serial number(s): JW851/0014

Connect to the instrument

在创建完Device object后就可以使用connect函数（connect - MathWorks）连接硬件了：

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% Connect device object to hardware.
connect(ps4000aDeviceObj);

当执行完成后就会在命令行中打印连接的信息：

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Serial number(s): JW851/0014

Opening PicoScope 4000 Series (A API) device...

   Instrument Device Object Using Driver : picotech_ps4000a_generic.mdd
 
   Instrument Information
      Type:               Oscilloscope
      Manufacturer:       Pico Technology Ltd.
      Model:              PicoScope 4000 Series (A API)
 
   Driver Information
      DriverType:         MATLAB generic
      DriverName:         picotech_ps4000a_generic.mdd
      DriverVersion:      1.2.16.10
 
   Communication State
      Status:             open

Setting Device Parameters...

Default Channel Setup:-
-----------------------

Channel A:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Channel B:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Channel C:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Channel D:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Channel E:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Channel F:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Channel G:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Channel H:-
	Enabled: True
	Coupling: DC
	Range: 5V
	Analog Offset: 0.0V

Default Block mode parameters:-

               Timebase index : 79
                 Time Interval: 1000.0 ns
 Number of pre-trigger samples: 0
Number of post-trigger samples: 1000000
       Total number of samples: 1000000

Default Streaming mode parameters:-

 Streaming interval: 1.00e-06 s
Streaming auto stop: 1

Default Signal generator parameters:-

      Start frequency: 1000 Hz
       Stop frequency: 1000 Hz
       Offset voltage: 0 mV
 Peak to Peak voltage: 2000 mV
Initialization complete.

Connected to PicoScope 4000 Series (A API) device:-

      Instrument Model: 4824A
   Batch/Serial Number: JW851/0014
       Analog Channels: 8
             Bandwidth: 20 MHz
         Buffer memory: 256 MS
 Maximum sampling rate: 80 MS/s
 Signal Generator Type: Arbitrary Waveform Generator

主要包含：

  • 更新后的Device object信息；
  • 默认Channel设置；
  • 默认Block mode参数；
  • 默认Streaming mode参数；
  • 默认Signal generator参数；
  • 以及硬件参数；


Disconnect Device

在使用完通信功能后，需要关闭并删除Device object：

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%% Disconnect device
% Disconnect device object from hardware.
disconnect(ps4000aDeviceObj);
delete(ps4000aDeviceObj);

这样的打开关闭的操作类似于各种软件读取文件的操作：先打开文件，再读取数据，最后再关闭文件。所以，从另一种角度来讲，我们可以把PicoScope所采集的数据理解成一种“动态”的文件。


Appendix

完整的代码如下：

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%% Clear command window and close any figures
clc, clear, close all

%% Load configuration information
% Setup paths and also load struct and enumeration information. Enumeration
% values are required for certain function calls.
[ps4000aStructs, ps4000aEnuminfo] = ps4000aSetConfig(); % DO NOT EDIT THIS LINE.

%% Device connection
% Check if an Instrument session using the device object 'ps4000aDeviceObj'
% is still open, and if so, disconnect if the User chooses 'Yes' when prompted.
if (exist('ps4000aDeviceObj', 'var') && ps4000aDeviceObj.isvalid && strcmp(ps4000aDeviceObj.status, 'open'))
    openDevice = questionDialog(['Device object ps4000aDeviceObj has an open connection. ' ...
        'Do you wish to close the connection and continue?'], ...
        'Device Object Connection Open');
    if (openDevice == PicoConstants.TRUE)
        % Close connection to device
        disconnect(ps4000aDeviceObj);
        delete(ps4000aDeviceObj);
    else
        % Exit script if User 
        return;
    end
end

% Create a device object. 
% The serial number can be specified as a second input parameter.
ps4000aDeviceObj = icdevice('picotech_ps4000a_generic.mdd', '');

% Connect device object to hardware.
connect(ps4000aDeviceObj);

%% Disconnect device
% Disconnect device object from hardware.
disconnect(ps4000aDeviceObj);
delete(ps4000aDeviceObj);