Re: INFICON Transpector MPH Residual Gas Analyzer (RGA) - http GET requests.

[Andrew Johnson via Tech-talk <tech-talk at aps.anl.gov>]

    Note that recent (3.15+) versions of Base have a JSON C
    stream-parser included in libCom, yajl:
    
    https://epics.anl.gov/base/R7-0/6-docs/doxygen/yajl__parse_8h.html
    
    Wasn't Eric Norum working on one or more http-based device supports?
    I'm sure they didn't use JSON at the time though.
    
    - Andrew

On 5/9/22 3:01 PM, Mark Rivers via Tech-talk wrote:

Hi Janez,

 

I recently wrote an areaDetector plugin that needs to parse JSON.  It is here:

https://github.com/areaDetector/ADCore/blob/master/ADApp/pluginSrc/NDPluginBadPixel.cpp

 

I used this very nice C++ parser:

https://github.com/nlohmann/json

 

It is just a C++ header file, so no library is needed.

 

I think you could write a simple asynPortDriver that uses drvAsynIPPort for the HTTP gets and the JSON parser to do what you want.

 

Mark

 

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Govednik, Janez via Tech-talk
Sent: Monday, May 9, 2022 2:50 PM
To: tech-talk at aps.anl.gov
Subject: INFICON Transpector MPH Residual Gas Analyzer (RGA) - http GET requests.

 

Hello,

 

We want to develop an EPICS support for Residual Gas Analyzer from Inficon. Unfortunately, RGA is running a web server which is listening for http GET requests on port 80. The response from the web server is in JSON format. My question is if somebody already develop an IOC for this type of device? If not, what would be the best solution? We were thinking that using simple stream device support and .proto file might be too messy in this case. Is there a library for http requests and simple JSON parser if we make our own support?  Do you have an example of http device support or use of JSON parser?

 

Here are two examples of the request and response (what you see in the web browser):

• /mmsp/scanSetup/channel/1/get

{

    "data": {

        "@id": 1,

        "channelType": "Sweep",

        "startMassRaw": 0,

        "stopMassRaw": 10000,

        "ppamu": 10,

        "dwell": 4.000,

        "emVoltage": null,

        "focusVoltage": null,

        "ionEnergy": null,

        "extra": 0,

        "leadIn": 0,

        "enabled": "True",

        "scaleFactor": 1,

        "relativeRef": 0,

        "reportType": "Absolute",

        "reportUnits": "Current",

        "equivIonFactor": -1,

        "digOutNum": -1,

        "digOutThresUpper": 1,

        "digOutThresLower": -1,

        "startMass": 0.00,

        "stopMass": 100.00,

        "channelMode": "Sweep",

        "rfEquivAMU": 0,

        "dcEquivAMU": 0,

        "rfEquivDAC": 0,

        "dcEquivDAC": 0

    },

    "name": "got",

    "origin": "/mmsp/scanSetup/channel/1"

}

 

·         /mmsp/measurement/scans

·             {

        "name": "got",

        "origin": "/mmsp/measurement/scans",

        "data": [

            {

                "scannum": 31,

                "scansize": 503,

                "values": [

                    538398,

                    4.475908e-10,

                    6.700834e-14,

                    -6.796693e-14,

                    ...

                ]

            },

            {

                "scannum": 32,

                "scansize": 503,

                "values": [

                    556335,

                    1.643438e-09,

                    -1.408637e-13,

                    ...

                ]

            }

        ]

    }

Thanks in advance! 

Best,

Janez

 

-- 
Complexity comes for free, Simplicity you have to work for.