Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Thu, 16 Sep 2010 11:20:00 -0500

On Thursday 16 September 2010 08:57:37 Ralph Lange wrote:
>
> I would think that camonitor for the complex structures would yield a
> hard to read, if not unusable output.

We could provide an option to output the complex structures using JSON, 
although it might be better to provide this functionality in a separate 
program.  Suggested output:

tux% cajson -d DBR_CTRL_DOUBLE -mvap anj:aiExample
{
  "anj:aiExample": {
    "field_type": "DBF_DOUBLE",
    "value": 0,
    "status": "UDF",
    "severity": "INVALID",
    "units": "Volts",
    "precision": 1,
    "lower_disp_limit": 0,
    "upper_disp_limit": 10,
    "lower_alarm_limit": null,
    "lower_warning_limit": null,
    "upper_warning_limit": null,
    "upper_alarm_limit": null,
    "upper_ctrl_limit": 0,
    "lower_ctrl_limit": 10,
  }
}

I'm using "null" for NaN values since JSON doesn't permit them in numerics, 
although I guess they could be expressed as "nan" instead.  I think each CA 
monitor event should output a complete JSON object, although I'm not sure 
whether parsers will like this.  The cajson program could use -m to mean 
monitor and do a ca_get_callback if you don't specify it.

Having created the above example I realize one problem with the DBR_CTRL_xxx 
types is that they don't include a time-stamp, so they're not very good for 
monitoring values that change over time.

- Andrew
-- 
The best FOSS code is written to be read by other humans -- Harald Welte

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System