Converting .fit file generated by Zwift into .csv

I have been using Zwift to generate a .fit file of recorded stationary bike data. However, when I try to use the Fit SDK to convert the file, I get an error "Missing message definition for local message number 2. Error at byte: 167" and if I try to view the same file on the FIT File Viewer I get the error "Cannot read property 'fieldDefinitions' of undefined". Has anyone used Zwift before and encountered this problem?

0 Ben FIT over 3 years ago

I suspect that this one file may be corrupt. The error occurred in two different apps that use different versions of the FIT SDK. The FIT CSV Tool uses the Java SDK, and FIT File Viewer uses the C or C++ SDK. As a test, I downloaded a FIT file from Zwift's website and I was able to convert it to a CSV and open it in FIT File Viewer. I would try to download your file again from Zwift and see if that fixes it.

0 9648291 over 3 years ago in reply to Ben FIT

Thank you for your reply. I have tried both systems on 3 different files from Zwift, with the same results. It sounds like there is a problem on Zwift's end. Hopefully I can find what is causing the problem in Zwift and fix it. If you have any thoughts on that front It would be welcome.

0 Ben FIT over 3 years ago in reply to 9648291

Zwift sends the same FIT file to Garmin, Strava, TrainingPeaks, and 4-5 other sites. So I do not think it is a systemic issue, else there would be a lot of chatter about it. There might be something here that may be of help. support.zwift.com/.../my-activity-didn't-upload-H1Zv962fS

0 9648291 over 3 years ago

For the output to work properly the ride has to be greater than 2 miles. Once I did a test ride longer than 2 miles I was able to convert the output.