Manipulating Snapshot Files

The XML files that are created by the ER-101 Programmer are easily generated and modified if you are comfortable with XML and even easier if you are comfortable with dotNET/C#. While this page is a bit sparse at the moment, I will try to collect here knowledge and utilities for would-be hackers of ER-101’s snapshot files.

• The ER-101 Common Library: this is the same library (as a Visual Studio C# project) that the ER-101 Programmer uses to parse and generate snapshot files. You will want to start with the LoadFromXML(…) and SaveToXML(…) methods in the ER101 class.
• Download an example of a snapshot file from here.

Uploading voltage tables

It is also possible to design your voltage tables on the computer and upload them via USB to your ER-101. It just involves a little familiarity with XML files:

Step 1

Using the ER-101 Programmer application, download your ER-101’s snapshots as one large XML file.

Download the application from here: http://old.orthogonaldevices.com/er-101/Programmer

Step 2

In the XML file there is a “snapshots” node that contains 16 “Snapshot” child nodes, one for each of the snapshots on your ER-101. Each “Snapshot” node contains a “tracks” node with the following structure:

<tracks>

    <Track>
        <voltagesA>
            (voltage values here)
        </voltagesA>
        <voltagesB>
            (voltage values here)
        </voltagesB>
    </Track>

    <Track>
        <voltagesA>
            (voltage values here)
        </voltagesA>
        <voltagesB>
            (voltage values here)
        </voltagesB>
    </Track>

    <Track>
        <voltagesA>
            (voltage values here)
        </voltagesA>
        <voltagesB>
            (voltage values here)
        </voltagesB>
    </Track>

    <Track>
        <voltagesA>
            (voltage values here)
        </voltagesA>
        <voltagesB>
            (voltage values here)
        </voltagesB>
    </Track>

</tracks>

Notice there are 4 tracks and each track has two voltage tables (A and B). The values in voltage table are the actual 16-bit integers that are sent to the DAC (0 corresponds to 0.000V, 8000 corresponds to 1.000V and so on). You can edit the values with a text editor or custom script and then upload the modified XML file back to your ER-101 (again using the Programmer application).

The basic equation for converting frequency to voltage:

frequency = (frequency of C0 or 16.35Hz) * (2 ^ voltage) voltage = log2 (frequency/16.35)

The basic equation for converting cents to voltage:

cents = voltage/1200 voltage = cents*1200

The basic equation for converting voltage to a DAC code that goes into the voltage table:

code = voltage*8000

Step 3

Once you have your modified snapshots back in your ER-101, you can copy the voltage tables to other tracks or even to the USER reference voltage tables.

FYI, the ER-102 makes this process a lot simpler because the reference voltage tables are actually just individual files on your SD card.