4iiii Viiva Heart Rate monitor revisited

Some time ago I posted about my general dissatisfaction with the 4iiii Viiva heart rate monitor.

In a nutshell, in addition to being a ANT+ and Bluetooth Low Energy (BTLE) heart rate monitor, it also acts as a bridge between ANT+ devices that don’t offer BTLE functionality. In my original review of the Viiva, I complained because few software offerings provided support for it and the data is sent to apps wasn’t accurate.

Well, I need to revise my opinion of the Viiva … it has gained adoption and now appears to be quite useful.

Those who use training programs (such as Zwift) with Apple TV have already learned that the Apple TV only supports 3 total BTLE devices connected. One of those devices slots is already taken by the remote control. That leaves only 2 more slots.

If you’re using a training program, you’ll need at least 3 devices connected (possibly more) …

  • Cadence sensor
  • Heart rate monitor
  • Trainer
  • Speed sensor (depending on the trainer)
  • Power meter (depending on the trainer)

In my case, I need a cadence sensor, heart rate monitor, and Kickr smart trainer (which acts as both a smart trainer and power meter).

You can use the Zwift companion app to gate the BTLE sensors, through the phone, to Zwift … but I find that to be somewhat twitchy (see my post on Zwift, which I will create later and link).

With the Viiva HRM, I’m able to pair my cadence sensor (which broadcasts in both ANT+ and BTLE) to it and feed both it and the heart rate data to the Apple TV without needing an extra BTLE connection slot.

So far it’s working well … the only issue I’ve had is that sometimes it takes a little while for Zwift to pick up the Viiva heart rate monitor.

Another option to accomplish the same thing is to use the North Pole Engineering (NPE) CABLE ANT+ to BTLE gateway. I tried using that but had problems with the hardware. It was probably defective. Getting support for the device, from the manufacturer, was pretty difficult. I ended up giving up, returning the device, and using the Viiva (since I already had it).

One thought on “4iiii Viiva Heart Rate monitor revisited

  1. David Post author

    As it happens, Wahoo recently released a firmware update for the Kickr 2018 that calculates cadence and feeds it to training programs.

    I tried it out and it more or less works … but changes to cadence lag significantly behind what a true cadence sensor will report. This is due to the fact that the Kickr is calculating cadence using various pieces of information. It’s, apparently, adequate for many users (according to the experts).


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