Stack Data ConversionUpdated: Dec 25, 2001
A few years ago when I had an SCCA Spec Racer Ford, I built my own data acquisition system and created my own analysis software including a scheme to import Stack data so that I could compare my data to other racer's Stack data. Since the Stack data format is their own proprietary format, they could change it at any time and make the following information obsolete. I have no affiliation with Stack, I simply looked at their data files and deduced their format. Here's what I remember about the Stack data formats: For each session, Stack saves a "Runxxx.def" file (where xxx is the session number) that defines scaling factors for each of the transducers in that session. The def file is an Ascii text file that is easily readable. The def file defines exactly what sort of scaling is used for the data from each transducer. Most of the scaling is simply linear with an offset (AX+B) but some are a scaled inversion (A/X) and some may have higher order polynomials. I do not recall the meaning of each of the coefficients in each line of the file, but by comparing the data values using the Stack software, and looking at the converted data values of the data files with Excel, it is easy to deduce the proper scaling factors for your car. In the def file, the data channels are normally 16 bit data unless the channel is labeled as a DCHANNEL in which case it is 32 bit data. For the first session, Stack saves a series of "xxx.001" transducer data files, using a separate data file for each transducer. For example, wspd.001 is the wheel speed data, batt.001 is the battery voltage data, espd.001 is the engine speed.... etc. For the second session, you will have a series of "xxx.002" files... and so forth as the file extension is incremented for each session. The data in each transducer data file is a continuous stream of byte-reversed (least significant byte first) integers with no delimiters. For the transducer data that I was looking at, all of the data was a 16 bit integer, but perhaps some of the data may have other formats. For example, the distance data and the radius data are generally 32 bit integers. I created a rudimentary Visual Basic program called the "Stack-to-Ascii Data Converter" which converts any 16 bit Stack data file into a Windows compatible comma delimited file (also called comma separated values or CSV) that can easily be imported into Excel or Access for analysis. Once you import the comma separated data values into a program such as Excel, you can easily do the scaling that is described in the Stack "def" file. A couple of years ago, somebody sent me the following information about the Stack def file that may help you analyze and scale your Stack data properly: And here is a link to the page where you can download the data converter software:
Richard Shelquist
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