Re: Generation of state diagram documentation from SNL

["Hao, Hao via Tech-talk" <tech-talk at aps.anl.gov>]

Hi, Ed,

 

TDM (https://github.com/diverhao/tdm/releases/tag/v2507) has a “Seq Graph” tool to visualize and run a state machine in the frontend. This tool roughly follows the snl grammar to define the state machine, such as ss/state/when(). The logic must be written in _javascript_. It provides several functions to read/write PVs. For example, await delay(2) to delay 2 seconds, value_of(“pv_name”) to obtain the value, caput(“pv_name”, 33) to PUT a value, connect(“pv_name1”, “pv_name2”) to connect and monitor the PVs.

 

You can also visualize an existing C-like snl code using the “Emulation mode”, but you cannot run the code.

 

How to run a _javascript_ state machine code:

 

https://github.com/diverhao/misc/blob/main/tdm/run-state-machine.gif

 

How to visualize a SNL code:

 

https://github.com/diverhao/misc/blob/main/tdm/visualize-snl-state-machine.gif

 

The following code is a simple _javascript_ traffic light state machine:

 

// --------------------------------------------

// global variables must be written in global.xxx

global.R = 0;

global.Y = 1;

global.G = 2;

 

global.lights = [    

    "traffic:red_light",

    "traffic:yellow_light",

    "traffic:green_light"

];

 

connect(...global.lights);

 

global.red_time = 3.0;

global.red_yellow_time = 1.0;

global.green_time = 4.0;

global.yellow_time = 1.0;

 

ss light {

// no code allowed here

state red {  

  // no code allowed here

        entry {

            caput(global.lights[global.R], 1);

            caput(global.lights[global.Y], 0);

            caput(global.lights[global.G], 0);

        }

        when (await delay(global.red_time)) {

            print("switch to red-yellow light");

        } state red_yellow

    }

    state red_yellow {

        entry {

            caput(global.lights[global.R], 1);

            caput(global.lights[global.Y], 1);

            caput(global.lights[global.G], 0);

        }

        when (await delay(global.red_yellow_time)) {

            print("switch to green light");

        } state green

    }

    state green {

        entry {

            caput(global.lights[global.R],0);

            caput(global.lights[global.Y],0);

            caput(global.lights[global.G],1);

        }

        when (await delay(global.green_time)) {

            print("switch to yellow light");

        } state yellow

    }

    state yellow {

        entry {

            caput(global.lights[global.R],0);

            caput(global.lights[global.Y],1);

            caput(global.lights[global.G],0);

        }

        when (await delay(global.yellow_time)) {

            print("switch to red light");            

        } state red

    }

}

// --------------------------------------------

 

Best,

 

Hao

 

 

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Ed Janke via Tech-talk <tech-talk at aps.anl.gov>
Date: Thursday, June 26, 2025 at 8:56 PM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: [EXTERNAL] Generation of state diagram documentation from SNL

Hello! Does anyone know if there is software out there that can parse the SNL in an EPICS Sequence file to generate a state diagram for every state set? I was considering doing this by hand but figured I would ask the greater community in case

Hello!

 

Does anyone know if there is software out there that can parse the SNL in an EPICS Sequence file to generate a state diagram for every state set?

 

I was considering doing this by hand but figured I would ask the greater community in case this already exists.

 

 

 

Thanks,

Ed Janke