使用 VB 透過 SCPI 控制儀器設備

因要讀取電表的資料，所以接觸了SCPI這個語言，這次又要讀取示波器的波形資料，所以乾脆整理了一下使用的命令，方便於日後查詢

SCPI （Standard Command for Programmable Instrumentation）可程式化儀器標準語言，是透過ASCII語法來與儀器做溝通

簡單的命令範例如下

MEASure:VOLTage:DC?;:MEASure:CURRent:AC?

當然首先要先安裝電腦端的驅動程式，因為電表是使用Keysight的，所以就上Keysight網站找驅動程式了，下載網址

網站中有三套軟體，IO Libraries Suite是最主要的驅動，會安裝VisaComLib這個Library，主要是透過這個Library跟儀器做溝通的，所以至少要安裝這套軟體

在VB6中，要使用VisaComLib時，需要先引用它，所以要到 [專案] --> [設定引用項目] 中，選取 [VISA-COM 5.12 Type Library] 後才能開始寫應用程式

在VB6中宣告如下

 '--- General define ---
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long) 'declare to use "sleep"
Dim ioMgr As VisaComLib.ResourceManager
Dim instrument As VisaComLib.FormattedIO488
 
'--- function define ---
Dim ioMgr As VisaComLib.ResourceManagerDim instrument As VisaComLib.FormattedIO488
Dim sndBuffer As String
Dim rcvBuffer As String
Set ioMgr = New VisaComLib.ResourceManager
Set instrument = New VisaComLib.FormattedIO488
Set instrument.IO = ioMgr.Open("USB0::10893::4865::MY59022278::0::INSTR")
instrument.SetBufferSize IO_IN_AND_OUT_BUFS, 64

*IDN?是所有儀器通用的命令，透過這個指令來查詢儀器的 ID。儀器通常會回傳製造商名稱、儀器型號，以及製造商提供的韌體版本英數字元

instrument.WriteString "*IDN?"
Debug.Print instrument.ReadString

讀取電壓與電流的程式如下

'--------------------------
' Volt
'--------------------------
    status = commSend(instrument, "SENSe:VOLTage:DC:NULL:VALue:AUTO 1")
    status = commSend(instrument, "CONFigure:VOLTage:DC 10,0.001")        ' mV resolution
    status = commSend(instrument, "SAMPle:COUNt 1")
    status = commSend(instrument, "*WAI")
    rcvBuffer = commQuery(instrument, "READ?")
 
'--------------------------
' Current
'--------------------------
    status = commSend(instrument, "SENSe:CURRent:DC:NULL:VALue:AUTO 1")
    status = commSend(instrument, "CONFigure:CURRent:DC 1E-6")        
    status = commSend(instrument, "CURRent:DC:RES 1E-6")                        ' uA resolution
    status = commSend(instrument, "SAMPle:COUNt 1")
    status = commSend(instrument, "*WAI")
    rcvBuffer = commQuery(instrument, "READ?")

電表是使用USB連接，後來要控制R&S示波器，就想改用TCP/IP的方式試試，也是OK的喔，下面列出幾個範例，讀取波形電壓平均值、上升時間及波形的各點電壓資料

'==================================
' R&S RTM3004 波形平均值
'==================================
    instrument.WriteString "TRIGger:A:EDGE:SLOpe NEGative"
    instrument.WriteString "MEASurement1:SOURce CH2"
    instrument.WriteString "MEASurement1:MAIN MEAN"
    instrument.WriteString "MEASurement1:RESult? MEAN"
'==================================
'Measure rise time 
'==================================
    instrument.WriteString "TRIGger:A:EDGE:SLOpe NEGative"
    instrument.WriteString "MEASurement1:SOURce CH2"
    instrument.WriteString "REFLevel:RELative:MODE TEN"        ' 10% - 90%
    instrument.WriteString "MEASurement1:MAIN RTIMe"
    instrument.WriteString "MEASurement1:RESult?"  
'==================================
' Wave RAW data
'==================================  
    instrument.WriteString "TRIGger:A:MODE NORMal"           ' Normal trigger
    instrument.WriteString "TRIGger:A:EDGE:SLOpe NEGative"      ' Negative edge
 
    instrument.WriteString "FORM ASC"                              ' output format ASCii
    instrument.WriteString "FORM:BORD LSBF"
    instrument.WriteString "CHAN1:DATA:POIN DEF"
 
    instrument.WriteString "SINGle"                     ' Single trigger
 
    instrument.WriteString "CHANnel1:DATA:HEAD?"
    Debug.Print instrument.ReadString
 
    instrument.WriteString "CHANnel1:DATA?"
    Debug.Print instrument.ReadString

下面是UART、USB與TCP/IP的宣告方式

'=========
 'UART
 '=========
    Set instrument.IO = ioMgr.Open("ASRL6::INSTR")  ' COM6
 
    Dim serInfc As VisaComLib.ISerial
    Set serInfc = instrument.IO
    serInfc.BaudRate = 9600                         ' 9600bps baud rate
    serInfc.FlowControl = ASRL_FLOW_NONE
    serInfc.Timeout = 10000
    instrument.IO.SendEndEnabled = True
    instrument.IO.TerminationCharacter = 10          ' could be 10 (line feed) or 13 (carriage return)
    instrument.IO.TerminationCharacterEnabled = True
    instrument.IO.Timeout = 10000
 
 '=========
 'USB
 '=========
    Set instrument.IO = ioMgr.Open("USB0::0x0AAD::0x01D6::104068::INSTR")
    instrument.SetBufferSize IO_IN_AND_OUT_BUFS, 64
    Set serInfc = instrument.IO
 
 '=========
 'TCP/IP
 '=========
 
    Set instrument.IO = ioMgr.Open("tcpip0::192.168.0.13::instr")        ' ip addr 192.168.0.13
    instrument.SetBufferSize IO_IN_AND_OUT_BUFS, 64
    Set serInfc = instrument.IO

下面是用Arduino與ADS1015做的4通道電表，解析度至小數第二位，使用VBA透過UART讀取電表至Excel表格中

Arduin 用的SCPI Library 有蠻多個 (Vrekrerscpiparser) (Open Instrument Control)，下面範例是使用OIC的Library完成的