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PostPosted: Tue Nov 28, 2017 8:36 am 
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That breakdown is interesting.

There are 4 power pages in ANT+. Basic (everyone, mandatory), Crank Torque (cranks, arms, pedals), Wheel Torque (Powertap hub only) and Crank Torque Frequency (SRM only). Everyone must have at a minimum basic pages, and almost all use 1 of the 3 others with every 4th page is basic to maintain backwards compatibility with simpler head units -- least that was the idea. Basic pages are also the only place balance is found. It's a violation of ANT+ spec to include multiple option pages and it wouldn't have certified. So 1 + basic.

So based on what has been shown so far I would guess that the Shimano uses Crank Torque pages. Since SRM only has to deal with Crank Torque Frequency in their own products, when connecting another meter it's likely dropping back to Basic pages. I don't have a PC8 so can't check.

The possibility is that either the Shimano PM is not encoding basic pages properly or the SRM head unit is not decoding them correctly.

Also, when testing, what a Garmin records is NOT what it displays. They have different requirements. The specific example the Garmin Edge engineer used at the ANT+ symposium a few years ago when I was there was to imagine going down a hill and you stop pedaling, when you look down you want to see what your cadence was not zero -- so it holds it for a few seconds even though it knows the data is stagnant and not changing. What is displayed in all Garmin head units is filtered, what is recorded on the newer (510/810 and newer) follows good guidelines for proper recording.

These spikes should be easy to track down using the ANT+ development software because it can decode both pages unlike a head unit. My guess is the PM and not the SRM head unit. Likely escaped because nobody saw it in crank torque pages.


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Posted: Tue Nov 28, 2017 8:36 am 


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PostPosted: Tue Nov 28, 2017 6:49 pm 
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The first is my PC8 paired to Pioneer dual leg power meter.

The second is my PC8 paired to SRM power meter.

Image
Image

Definitely the spikes are being caused by non SRM power meter.

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PostPosted: Tue Nov 28, 2017 7:07 pm 
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Thank you very much kwakekeham and PinaF8. This gives me a new avenue to investigate and discuss with SRM and Shimano.

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PostPosted: Tue Nov 28, 2017 7:56 pm 
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kwakekeham, check out the tab "Bicycle Power" on the ANT+ Device Profile page https://www.thisisant.com/developer/ant-plus/device-profiles. More info on the power message types. I am trying to download the complete documentation, but it looks like I need to be registered first.

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PostPosted: Fri Dec 01, 2017 1:17 am 
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Watching this thread makes me hope that the R9100-P will finally be really available....


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PostPosted: Wed Dec 06, 2017 8:16 pm 
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Is anyone doing a zero offset with a Garmin? When I do this, I always see an offset of 5050, no matter the temperature. I expected the offset to vary a little bit (like my previous SRM 7900 PowerMeter did), but the value reported by the Garmin is always the same. Is this expected? (The LED on the Shimano does blink, so I do know that the zero offset is actually happening.)

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PostPosted: Wed Dec 06, 2017 9:26 pm 
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It’s designed like that so you know everything is ok.


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PostPosted: Thu Dec 07, 2017 2:00 am 
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mds wrote:
Is anyone doing a zero offset with a Garmin? When I do this, I always see an offset of 5050, no matter the temperature. I expected the offset to vary a little bit (like my previous SRM 7900 PowerMeter did), but the value reported by the Garmin is always the same. Is this expected? (The LED on the Shimano does blink, so I do know that the zero offset is actually happening.)


Just do it with the button on the crank. So much easier.


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PostPosted: Thu Dec 07, 2017 4:34 am 
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cunn1n9 wrote:
Just do it with the button on the crank. So much easier.

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Exactly. That's one of the features I really like about this Shimano Powermeter. Instead of going thru layers of menu in the head unit. My pre-ride routine now includes spinning the crankarms to 12 and 6 o'clock, pressing the button while putting on my shoes. It is so easy and quick comparing the Pioneer I had previously. The Pioneer unit requires zeroing left and right separately which takes couple minutes using the not so friendly Pioneer head unit.


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PostPosted: Thu Dec 07, 2017 10:44 am 
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ipenguinking wrote:
cunn1n9 wrote:
Just do it with the button on the crank. So much easier.

Sent from my iPhone using Tapatalk


Exactly. That's one of the features I really like about this Shimano Powermeter. Instead of going thru layers of menu in the head unit. My pre-ride routine now includes spinning the crankarms to 12 and 6 o'clock, pressing the button while putting on my shoes. It is so easy and quick comparing the Pioneer I had previously. The Pioneer unit requires zeroing left and right separately which takes couple minutes using the not so friendly Pioneer head unit.


Thinks like this add up for me. I'm like... 300 rides a year, 5 years life on the bike at least, 1500 rides... difference in price between pioneer and Shimano ($700 for moi).

That 1500 rides; if lets assume it's 1min for both (1,500min = 25 hours).

= $28 per hour ($.46 a minute).

Assuming it actually takes 2min to calibrate ($.23).

So; would I rather pay 25-50 cents to just get going, or save that and waste a few minutes?

:o :lol:

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PostPosted: Thu Dec 07, 2017 11:48 am 
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Conza wrote:
ipenguinking wrote:
cunn1n9 wrote:
Just do it with the button on the crank. So much easier.

Sent from my iPhone using Tapatalk


Exactly. That's one of the features I really like about this Shimano Powermeter. Instead of going thru layers of menu in the head unit. My pre-ride routine now includes spinning the crankarms to 12 and 6 o'clock, pressing the button while putting on my shoes. It is so easy and quick comparing the Pioneer I had previously. The Pioneer unit requires zeroing left and right separately which takes couple minutes using the not so friendly Pioneer head unit.


Thinks like this add up for me. I'm like... 300 rides a year, 5 years life on the bike at least, 1500 rides... difference in price between pioneer and Shimano ($700 for moi).

That 1500 rides; if lets assume it's 1min for both (1,500min = 25 hours).

= $28 per hour ($.46 a minute).

Assuming it actually takes 2min to calibrate ($.23).

So; would I rather pay 25-50 cents to just get going, or save that and waste a few minutes?

:o :lol:


Well to zero the shimano pm with the button on the crank takes literally 5s max. One of the best things about it


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PostPosted: Thu Dec 07, 2017 3:10 pm 
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With the 'Prompt for calibration' feature of the Garmin Edge series, the SRM zero-offset routine can be done as you roll out to start a ride, but pushing a button still sounds a lot easier.

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PostPosted: Thu Dec 07, 2017 3:51 pm 
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This feature of zero calibration done by pushing a button on the DA sounds good to me. Much better than the Stages via Garmin!! Otherwise I think the best is the P2M automatic calibration.


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PostPosted: Thu Dec 07, 2017 4:05 pm 
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TonyM wrote:
Otherwise I think the best is the P2M automatic calibration.

Garmin has an option to Auto Calibrate as well, but some have found that to be problematic. I have personally seen it start the auto-calibration process during which I start pedaling at high load, which yields a completely inaccurate offset, for which one is left wondering why the Garmin is displaying a 1/3 of the expected power output during the next sustained high power effort. :noidea:

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PostPosted: Thu Dec 07, 2017 5:40 pm 
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ms6073 wrote:
TonyM wrote:
Otherwise I think the best is the P2M automatic calibration.

Garmin has an option to Auto Calibrate as well, but some have found that to be problematic. I have personally seen it start the auto-calibration process during which I start pedaling at high load, which yields a completely inaccurate offset, for which one is left wondering why the Garmin is displaying a 1/3 of the expected power output during the next sustained high power effort. :noidea:


Thanks for the info! :thumbup:
I just see it in my Garmin Edge 820. Actually I never tried it before but I might give it a try next time I use my Stages on my MTB.


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Posted: Thu Dec 07, 2017 5:40 pm 


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