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  • Author Author: Jan Cumps
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SCPI on a Linux Board - Letter of Intent

Jan Cumps

I'm trying to build a SCPI shell for Linux.

I'd like to have it working over TCP/IP on a Raspberry Pi and a BeagleBone.

 

tl;dr It works. The rest of the blog series explains how to build a lab automation device that controls 8 outputs (2 of them relays), and read 8 inputs. With a Raspberry Pi and a PiFace Digital (2).

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Here on element14, we've been playing with SCPI and microcontrollers. We have several instruments working on MSP432, Arduino and Hercules devices.

This time I'd like to get a Linux instrument up. To get some device independence, I'll try to make the source work on two different boards with different distros.

The program is expected to run as a background process.

 

I have a head start. My favourite SCPI library has a LwIP SCPI server example.

A relative head start, that is, because I have to find out how to get all the dependencies - I want to develop on a Windows PC image.

If this project fails, it'll be because of my develop for Linux skills.

 

related blog
SCPI on a Linux Board - Letter of Intent

SCPI on a Linux Board - Part 1: Proof of Concept

SCPI on a Linux Board - Part 2a: PiFace Digital C programming

SCPI on a Linux Board - Part 2b: PiFace Digital C++ programming
SCPI on a Linux Board - Part 3: TCP/IP Socket C++ programming
SCPI on a Linux Board - Part 4: TCP/IP SCPI and Instrument Service
SCPI on a Linux Board - Part 4b: TCP/IP SCPI and Instrument Service 100% Working
SCPI on a Linux Board - Part 4c: TCP/IP SCPI and Instrument Service - Run as a Daemon
SCPI on a Linux Board - Part 5a: LabVIEW Driver for LAB Switch: Open, Close and Switch functions

  • A few learnings from testing LabVIEW with another TCP/IP device (a Tektronix TBS 2000 oscilloscope - I won it in a contest image ):

    I can get things to work with raw TCP/IP - not yet as a VISA instrument.

    The Tektronix has all VISA drivers installed and I can contact it over VISA via TCP/IP, but not reliable.

    With USB, that scope works just fine.

    Have I opened a can of worms?

  • Well, that didn't take long.

    image

    I have a SCPI parser running now that accepts SCPI commands and sends replies. Easier than I thought it would be.

    Achievements unlocked:

    • program runs on Raspberry Pi, listens on a tcp/ip port for SCPI and can reply
    • SCPI library incorporated
    • cross compiled: developed on windows, executed on linux/Pi, debugged remotely from Windows

    To do:

    • turn this into a daemon, with proper startup and shutdown
    • test on BeagleBone
    • make a test instrument. This is just a mock program pretending it's a digital multimeter.
    • implement SYSTem:COMMunicate:LAN:CONTrol? : dynamic allocation of control port.
  • in reply to Jan Cumps

    for the geeks (i.e.: me):

     

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    from a raw telnet console on a linux pc in the network, the payload 'test' is sent to the Pi on port 2222.

    In Eclipse debugger on Windows, this is captured and logged ("Here is the message: test" ).

    On the telnet that sent the message, a confirmation is received ("I got your message").

     

    That's all I need to get a SCPI communication shell. Now over to getting it executed as a daemon ...

  • TCP/IP basics work on Raspberry Pi.

    Compiled and debugged in Eclipse on a Windows 10 PC, compiled program executed on the Pi:

    image

     

    Inspiration: http://www.cs.rpi.edu/~moorthy/Courses/os98/Pgms/server.c

     

    This may not look spectacular, but I think it's cool that you can compile a C executable on a windows machine, transfer it to the Pi and step through the code in the debugger on that same windows machine - with 1 click on some button