WebDAQ .wdd File Format

[Fausto]

The WebDAQ binary data file format stores time-domain data from the WebDAQ device. This document provides a description of the file format so that it may be easily read for conversion or direct use. All values are in the format are little-endian.

The data file starts with a simple fixed-size binary header:

 

This is followed by a JSON header of varying size. More information about the JSON format can be found at https://www.json.org/. The size of the JSON header is supplied in the binary header. The JSON header contains additional scan information including channel names, units, and device information. It consists of two objects, jobDescriptor and systemInfo. 

The systemInfo object contains information about the hardware which ran the acquisition. This includes the device name, product name, serial number, MAC address. See the systemInfo object in the JSON Header Example below.

The jobDescriptor object describes the job which created the file. The schema for this object is available on the WebDAQ, and can be accessed by entering the address (in a web browser) “<webdaq_address>/api/v1.0/jobs/schema” where <webdaq_address> is the IP address or hostname of your device. Note that the schema varies by device model. See the jobDescriptor object in the JSON Header Example below. More information about JSON schema can be found at https://json-schema.org/. 

After the header information, the data is arranged as tightly packed IEEE-754 double values. The data is interlaced, such that a single point per channel is written at a time.

JSON Header Example

{
    "jobDescriptor": {
        "acquisition": {
            "sample": {
                "autoZeroMode": "everySample", 
                "rate": 50
            }, 
            "startTrigger": {
                "type": "immediate"
            }, 
            "stopTrigger": {
                "sampleCount": 1000, 
                "type": "sampleCount"
            }
        }, 
        "alarms": [], 
        "channels": [
            {
                "customScaling": {
                    "linear": {
                        "multiplier": 1, 
                        "offset": 0
                    }, 
                    "type": "none"
                }, 
                "name": "Thermocouple 0", 
                "number": 0, 
                "range": "\u00b178.125mV", 
                "tcType": "J", 
                "type": "thermocouple", 
                "unit": "C", 
                "www": {
                    "color": "#DD3222", 
                    "dashboardScalar": true, 
                    "dashboardStripChart": true
                }
            }, 
            {
                "customScaling": {
                    "linear": {
                        "multiplier": 1, 
                        "offset": 0
                    }, 
                    "type": "none"
                }, 
                "name": "Voltage 1", 
                "number": 1, 
                "range": "\u00b178.125mV", 
                "type": "voltage", 
                "unit": "V", 
                "www": {
                    "color": "#FFC000", 
                    "dashboardScalar": true, 
                    "dashboardStripChart": true
                }
            }
        ], 
        "logging": {
            "enable": true, 
            "logFile": {
                "appendTime": true, 
                "name": "MultiChannel", 
                "path": "/storage/data/"
            }, 
            "note": ""
        }, 
        "name": "MultiChannel", 
        "productId": 314, 
        "type": "job", 
        "version": 1, 
        "www": {
            "iterationIndex": 0, 
            "status": 1, 
            "statusText": "Queued"
        }
    }, 
    "systemInfo": {
        "MAC": "00:80:2F:AA:AA:AA", 
        "SerialNo": "01C176C5", 
        "name": "webdaq-demo", 
        "productName": "WebDAQ-316"
    }
}