[BUG] Watt values are not correct on Schwinn IC4

[Rowdy]

Description I'd like to see the values for Watt and resistance. I've configured the tiles to show these values but they are way off. I read that the resistance is not being sent via bluetooth and therefore calculated. Nevertheless the Watt values are also way off.

Steps to reproduce the behavior: I'm using a Schwinn IC4 as my bluetooth bike. When I start a training the display of the watt values and also resistance is way off. In the screenshot the wattage should be around 70-100.

Expected behavior The watt value should be accurate from the Schwinn IC4. It works in Kinetic or other apps without qdomyos.

Screenshots

[cagnulein]

hi @Rowdy i need a debug log with the issue. Thanks

[Rowdy]

I think the watt values are actually accurate. but the resistance is not. The Schwinn bike only has levels from 0 - 100. debug-Mo__Juni_3_20_45_19_2024.log

[cagnulein]

Yes becauee your bike doesn't send resistance over Bluetooth so qz is calculating it from cadence and wattage. You can play with the schwinn settings on qz to change the algorithm but of course will not be the same of the bike.

It's unfortunately a lack on the schwinn firmware

[Rowdy]

@cagnulein got it thanks! The SmartSpin2k advanced settings won't help with that, right? What are these about?

[cagnulein]

Nope only if you use the ss2k

@doudar can give you more Info about this device!

[Rowdy]

@cagnulein I'm using this genius device as well

[cagnulein]

Hah Ok so you set the step setting in order to have 100 steps to go to the full resistance?

[cagnulein]

@cagnulein got it thanks!

The SmartSpin2k advanced settings won't help with that, right? What are these about?

So yes the advanced ones are right for your setup. There is a ticket here on github about a user with ic4 and ss2k with this settings

Let me know if you can't find it

[doudar]

Creating our own (hopefully much more accurate) method for calculating watts on the IC4 is on my timeline, however I'm currently not sure when I'll get development time for it. My work currently is a lot bit crazy.

If Roberto wanted to attempt it with QZ, it could be possible. My basic theory is to (on power up) lower motor current (operation 0x09 to a low value), drive the stepper CCW to the physical extreme (grind against the stop) (0x19 (-1000?), then use a power meter calibrated table to output watts by using our stepper position (0x19) and cadence (0x0F or via FTMS) to look up the value.

I think this method should be much more accurate than what Schwinn is using because: 1) Their cadence calculation seems to be way off. It doesn't follow reality at all. Without changing resistance, 50 RPM is typically close to accurate, 110rpm is way over being a sensible watt number. 2) I think there's a lot of variation in the potentiometers they are using for knob position sensing. By using our actual stepper position (very accurate), we should be able to get a very, very accurate position of the knob/brake mechanism.

Caveats: Does the end stop physically change/vary between bikes? How much does the magnet strength vary between bikes? Others I can't think of I'm sure.

But in general, their power calculation seems half hearted at best.

[Rowdy]

@cagnulein got it thanks! The SmartSpin2k advanced settings won't help with that, right? What are these about?

So yes the advanced ones are right for your setup. There is a ticket here on github about a user with ic4 and ss2k with this settings

Let me know if you can't find it

this one https://github.com/cagnulein/qdomyos-zwift/issues/392 ? not sure if that's the correct one

[cagnulein]

This one https://github.com/cagnulein/qdomyos-zwift/pull/666