Funky Power Data

I've been noticing a small blip about every 15 seconds (6 times in 90 seconds) in otherwise steady power data when it's displayed in ConnectIQ.

I was using the PeriPedal Software to generate the power data because I don't actually have a power meter. PeriPedal uses the speed data and the model of trainer to calculate an estimate of power. I had a method so PeriPedal could generate perfectly stable power at 75 Watts. But I would still see a blip down to 50 or 56 watts on the watch about every 15 seconds.

This pic doesn't have the perfectly stable 75 watt method implemented, but the blips are obvious.

So then I setup another computer with SimulANT to read the power data. I would watch the instantaneous power on the SimulANT Bike Power Display and there were no Blips.

So then I setup SimulANT to generate Power Data and I observed the data on the Watch - No Blips!!!

I got all of the settings in Simulant to exactly match the data stream that PeriPedal was putting out.

The 15 second period of the blips made me suspect that the Common Data pages were the problem so I looked at the data streams from SimulANT and from PeriPedal.

The following stream of Bytes from Simulant does NOT cause a blip on the watch.

4512297 : Rx: [10][EF][FF][FF][35][79][4B][00]

4512547 : Rx: [10][EF][FF][FF][35][79][4B][00]

4512796 : Rx: [10][F0][FF][FF][80][79][4B][00]

4513046 : Rx: [10][F0][FF][FF][80][79][4B][00]

4513296 : Rx: [50][FF][FF][01][48][00][01][00]

4513545 : Rx: [10][F1][FF][FF][CB][79][4B][00]

4513795 : Rx: [10][F2][FF][FF][16][7A][4B][00]

4514044 : Rx: [10][F2][FF][FF][16][7A][4B][00]

4514294 : Rx: [10][F2][FF][FF][16][7A][4B][00]

The following stream of Bytes from PeriPedal DOES cause a blip on the watch

5607830 : Rx: [10][EE][FF][FF][17][8E][4B][00]

5608079 : Rx: [10][EF][FF][FF][62][8E][4B][00]

5608329 : Rx: [10][F0][FF][FF][AD][8E][4B][00]

5608579 : Rx: [50][FF][FF][01][48][00][01][00]

5608828 : Rx: [10][F2][FF][FF][F8][8E][4B][00]

5609078 : Rx: [10][F3][FF][FF][43][8F][4B][00]

5609327 : Rx: [10][F4][FF][FF][8E][8F][4B][00]

The Common Data Page Message is EXACTLY the same.

On the Power Data Pages:
- Bytes 6 and 7 are [4B[]00] which is the 75 Watts
- Bytes 4 and 5 are the accumulated power so I don't think that is the problem.
- Bytes 0, 2, and 3 are the same in both cases.
- Byte 1 is the update event count. I think this might be the trouble maker.

In the Simulant data, the update event count before the Common Data Page (Byte 0 = [50]) is [F0] and it's [F1] after the common data page.

In the PeriPedal data, the update event count is [F0] before the Common Data Page and [F2] after. (I must have just been lucky to have them both occur at [F0])

So it looks to me like the watch does not handle a missing Event count very well. It's not clear to me if this is a bug in PeriPedal because it skipped an Event count number (one was really missed while the Common Data Page was sent so doesn't seem like a bug???)

Even if it is a bug in PeriPedal, it seems like the watch should deal with this better. I'm thinking that a simple missed reading could cause the same problem but I haven't verified that.

This is on a 920XT with 4.2 firmware and SDK 1.1.3.

This might be a watch issue rather than a ConnectIQ issue. I haven't checked if a native app does the same thing. I'm tired of debugging this one so I'll leave it here.

MoxyRoger over 10 years ago

I forgot. Here's the code that gets the power data in the ConnectIQ App.

hidden function getCurrentPower() {

        var info = Activity.getActivityInfo();

        return info.currentPower;

    }

Former Member over 10 years ago

The ConnectIQ API you are using reads power data directly from our internal ANT API, so if there is an issue, it would have to be at that level. I've forwarded this report to the teams that maintain the ANT firmware so they can investigate.