CFNReader

Introduction

Provides a simple way to read FNIRSI's CFN files (*.cfn) produced by the FNIRSI UsbMeter tool (here). With this library you can also convert *.cfn files to CSV files easily. Available as NuGet package.

QuickStart

using var myfile = File.OpenRead("myfile.cfn");
var cfnreader = new CFNStreamReader(myfile);

// Read general file information
var fileinfo = await cfnreader.ReadFileInfoAsync();

// Read and print data points
await foreach (var datapoint in cfnreader.ReadDatapointsAsync(fileinfo))
{
    Console.WriteLine(
        string.Join("\t", [datapoint.Time.ToString("G"), datapoint.Values[Channel.VBusVoltage], datapoint.Values[Channel.VBusCurrent]])
    );
}

Output:

0:00:00:00,0000000      0.0000V 0.0126A
0:00:00:00,0100000      0.0100V 0.0126A
0:00:00:00,0200000      0.0200V 0.0126A
0:00:00:00,0300000      0.0300V 0.0126A
0:00:00:00,0400000      0.0400V 0.0126A
...

The CFNStreamReader class provides two methods to read the file: ReadFileInfoAsync and ReadDatapointsAsync. The first one reads the file header and returns a FileInfo object. The second one reads the data points and returns an IAsyncEnumerable<DataPoint>. Both methods are asynchronous and support cancellation using a CancellationToken.

Convert to CSV

A simple way to convert the data to a CSV is provided by the CFNCSVConverter:

using var myfile = File.OpenRead("myfile.cfn");
using var csvfile = File.Create("export.csv");

var csvconverter = new CFNCSVConverter(
    channels: [Channel.AccumulatedCapacity, Channel.VBusVoltage],
    predicate: dp => dp.Values[Channel.VBusVoltage] > 0.5,
    includeUnit: true,
    limitDataPoints: 1000
);

await csvconverter.ConvertToCSVAsync(testfile, csvfile);

The CFNCSVConverter class constructor accepts the following (optional) parameters:

• channels: An array of Channel values to include in the CSV. The order of the channels in the array will be the order of the columns in the CSV.
• predicate: A function that receives a Datapoint and returns a boolean. If the function returns true, the Datapoint will be included in the CSV.
• formatProvider: An IFormatProvider to use when formatting the values.
• separator: The separator to use between the values (default ;).
• encoding: The encoding to use when writing the CSV file (default UTF8).
• timeFormat: The format to use when formatting the time values (default G).
• valueFormat: The format to use when formatting the values (default N4).
• includeHeader: Wether to include the header row in the CSV.
• includeTime: Wether to include the time column (always first column).
• includeUnit: Wether to include the unit of the value(s) like A (amps) or V (volts) for example.
• limitDataPoints: The maximum number of data points to include in the CSV (default int.MaxValue)

Acknowledgements

This library is based on didim99's work in usbmeter-utils.