SCPI on a Linux Board - Letter of Intent

27 Apr 2018

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).

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 .

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

Top Comments

Jan Cumps over 4 years ago in reply to Jan Cumps +4

Yay!

It works. Above is the capture of a LabVIEW back and forth communication - with the Raspberry Pi as a VISA TCP/IP device.
*IDN? command sent, and the reply from the Pi arrived at LabVIEW.
DAB over 4 years ago +3

Good luck Jan.

DAB
Jan Cumps over 4 years ago in reply to Jan Cumps +3
what's not working ok:
- even though I get a reply, the Visa Read block in LabVIEW throws a timeout error.
- when I close a connection (regardless of telnet, LabVIEW), the service on the Raspberry Pi goes…

Jan Cumps over 2 years ago in reply to Jan Cumps

I'm now doing a long-run measurement,
with PSU stepping from 3 to 10 V
with DAC1 then stepping between 200 and 1100, step size 1

Then measure the current at each step, and also the values of the ADC 1 that measures the current.
I hope that this time it translates to something more linear than before the current sense circuit was sanitised ...
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akshitagupta15june over 2 years ago

Have a look at my entry and please like and share #badass Woman Project Entry - Akshita Gupta
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Jan Cumps over 2 years ago

This was an electronics-light project. Just plug a PiFace Digital on a Pi.
The result is quite useful in the lab though.
Here's an action photo of the project, where it switches a DMM between an OpAmp's input and output, time after time.
To measure the gain and dc offset 2000 times, under different conditions.
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Jan Cumps over 4 years ago

I've documented the first working version: SCPI on a Linux Board - Part 1: Proof of Concept
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Jan Cumps over 4 years ago in reply to Jan Cumps

I had a read on the timeout. It happens when the expected numbers of characters haven't arrived after the given timeout.
Because TCP/IP in VISA doesn't support querying the number of characters waiting to be read (I've tried and I get Not Supported by this instrument), I have made this decision:
After reading from the TCP/IP pipe, throw away that particular timeout error, because it is expected. Comment f you would do this differently.
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