How to make an old ANT+ sensor broadcast over Bluetooth

You need to buy a small piece of electronic wizardry called a BRIDGE in order to get your old ANT+ sport accessory to talk to a Bluetooth watch or apps like Coros Apex 2 Pro, Apple Watch Ultra and Zwift. These data bridges are nothing new and have been around in the sports world for many years (eg 4iiii Viiiiva, 2015) but they overcome a few novel problems still created by today’s technologies.

In sports data techy terms, a bridge can do this

• Convert old ANT+ sensor data to BLE
• Convert a BLE signal to ANT+
• Combine multiple bits of data into one sensor stream so that the recipient thinks it talking to only one sensor.

So you can perhaps see that legacy devices could be given a new lease of life.

Even relatively new sensors that support BLE might only support one BLE connection when you need 2 or 3 if Zwift is involved. I’ll cover some of the other uses another day but today I was prompted to write this because I just wanted to get my ANT+ Vasa Swim Trainer to send power data to my Apple Watch. This is an extremely niche use case that about 4 other people in the entire world will be interested in but the principle applies to other ANT+ sports sensors.

Vasa Swim Trainer

In some ways, the ageing Vasa Swim Trainer was ahead of its time. Even a decade ago this swim trainer broadcast power, power balance, cadence and pace over ANT+. A pretty awesome feat, except virtually no modern tech that exists, can properly read swimming power into a swim profile. This is a combination that to be fair, we have to forgive developers for never considering.

Some time ago I explained how to get Vasa working in a Garmin environment by using a copy of an Outdoor Swim Profile combined with a CIQ data field for a secondary power meter. That used to work for Garmins but something happened to the mechanism that copies the power track from CIQ power to Standard Power, or maybe it was Golden Cheetah that stopped reading CIQ power and displaying it as power. IDK. It doesn’t work though.

The other night I had a moment of revelation. I thought I could trick one of the Apple sports apps into taking Vasa’s ANT+power transformed via NPE Cable (about $50) into BLE. It kinda worked.

More: NPE Cable

How To Use NPE Cable with Vasa

NPE Cable costs about fifty bucks and resembles an old chest strap heart rate pod in size.

 

 

Download the free, iOS CABLE Utility app and tap the $50 CABLE pod on your iPhone to pair. The menu is strangely squirrelled away at the top of the app all you need to do is get the POD to scan for ANT+ sensors and then say which capabilities of each sensor you want to convert to BLE.

That’s pretty much it. Now use an app on your Apple Watch that supports BLE sensors – like Workoutdoors or iSmoothRun. I chose the latter and pairing was relatively straightforward and voila! watts from the Vasa appear in the iSmoothRun app.

 

iSmoothRun saves your workout in Apple Health but you won’t be able to see the Power data Apple Fitness. However, the 3rd party HealthFit app can be used to automatically send every Apple Fitness workout ‘somewhere else’. I choose for mine to be sent to dropbox and from then I import them into Golden Cheetah on my desktop. Ta Da!…the power data is back

 

 

The Problem

Of course, there’s always a problem when you are trying to be too clever.

On Apple Watch, AFAIK it’s not possible to directly add power recording to a swim workout. Thus you have to record the Vasa workout as a bike ride or run then go through the whole process described above. Finally, in my case, in Golden Cheetah I change the Workout Type from Bike to Swim. This lets Golden Cheetah produce swim-specific CP charts and other swim-specific power metrics (which is what I want to achieve)

But. That manual step of changing the sport is one step too far for me!

Currently, iSmoothRun does not support recording swim workouts at all and WorkoutDoors does not allow you to add power to swim workout. I’m trying to convince Lambros to change that to give me my optimal solution;-)