nRF Toolbox app on IOS - CSCS Service - Speed calculation seems to be totally wrong?

RE: nRF Toolbox app on IOS - CSCS Service - Speed calculation seems to be totally wrong?

Simonr — Mon, 09 Nov 2020 13:14:41 GMT

Thank you for reporting this. This seems like a problem indeed. I will notify our app developers so that they can confirm, and hopefully fix this in an upcoming release. Please be patient as it might take some days to confirm this. Likely longer before a possible fix finds its way into a release.

Either way, we generally suggest using the nRFConnect mobile app for development, as it is more versatile, better suited for development purposes, and more frequently updated (this goes for both Android and iOS).

Best regards,

Simon

RE: nRF Toolbox app on IOS - CSCS Service - Speed calculation seems to be totally wrong?

daubsi — Sun, 08 Nov 2020 22:34:41 GMT

I think I can answer my own question, or in other words, show the error in the app!

According to the CSCS profile, CSCP_SPEC_V10.pdf, p14, it says:

"Calculation of speed at the Collector can be derived from the wheel circumference and data in two successive measurements. The Collector calculation can be performed as shown below: Speed = (Difference in two successive Cumulative Wheel Revolution values * Wheel Circumference) / (Difference in two successive Last Wheel Event Time values)"

Lets take the observed value of 12 revs/s in this formula:

12 * 2.312m / (1024/1024) = 27,744m/s * 3600s = 99878m = 99,8 km/h --> which is pretty exaclty the value Zwift (and the Tacx app print).

Given 4 revs we get: 4 * 2.312m / (1024/1024) = 9,248m/s * 3600m = 33292m = 33,29 km/h -> which is my presumed and probable true result.

What does the nRF Toolbox app print when I deliver 4 revs/s?

4 * x / (1024/1024) * 3600 = 14400m = 14.4 km/h --> x = 1! The nRF Toolbox app seems to ignore the wheel circumfence of 2.312m in the calculation of the speed!

This is consistent with my observation that changing the slider with the wheel size does not seem to have any drastic effect on the calculation and this is the bug in the app in my opinion...

RE: nRF Toolbox app on IOS - CSCS Service - Speed calculation seems to be totally wrong?

daubsi — Sun, 08 Nov 2020 17:32:53 GMT

devzone.nordicsemi.com/.../LightBlue_2D00_20201108_2D00_1730.csv

The attached file can be used as a data source in order to illustrate my observations

RE: nRF Connect on IOS - CSCS Service - Speed calculation seems to be totally wrong?

daubsi — Sun, 08 Nov 2020 17:24:28 GMT

Sorry, I am talking about the nRF Toolbox app the whole time - not nRF Connect! Sorry for the confusion. Installed nRF Toolbox version is v5.02 on iOS 14.1