4iiii Viiiiva Heart Rate Monitor BTLE to ANT+ bridge with new firmware upgrade

[Update: the next day I wasn’t able to reproduce this functionality – simply the ANT+ stream to the foot pod was not published. I’m waiting now for the response from 4iiii about this problem.]

[Update 2: after some reseting of the devices it started working again. I suspect the functionality is not yet stable. I have recorded a video how it works – can be found at the bottom of the page]

[Update 3: I got answer from 4iiii. Sadly the situation that I have described is not possible with the current Viiiiva and they are suggesting different explanation:

Looks like you may have found something undocumented in your BLE footpod. We wish we could take credit for this, but BLE to ANT+ pass-through isn’t currently possible for this generation of Viiiivas. Viiiiva isn’t equipped to be a Bluetooth Smart receiver, only a transmitter.
We’ve been trying to figure out what might account for your test results, and the only plausible explanation that we could come up with is that your BLE footpod may be transmitting a very weak ANT+ signal. Viiiiva has a sensitive ANT+ antenna and is equipped to boost footpod ANT+ signals. If there is an ANT+ signal, I expect your Viiiiva is picking it up and amplifying it enough to make it available to your Garmin. But we definitely haven’t enabled BLE to ANT+ bridging, sorry!


I will take a closer look into the BLE foot pod then in the near future.]

Today before I went running, out of curiosity, I have opened the Viiiiva configuration app. I pop-up with firmware upgrade to v1.11.0 hit my eyes – without hesitation I choose to do the upgrade.


After installation I’ve checked the configuration page and tried to discover the ANT+ devices.


I was surprised when I figured out that the app has found 2 foot pods (just 2 remind – I have 2 foot pods on my shoes but one is ANT+ and the second one BTLE). This option looks only for ANT+ foot pods. I immediately checked the Forerunner 310XT to search for foot pods –  Multiple Foot Pods detected.



After some investigation I found that in the new firmware Viiiiva actually converts the BTLE foot pod into ANT+! That’s for me the coolest feature that I was waiting on since I have bought the device – and the coolest one is that I haven’t really waited for it. I know there is a bridge from ANT+ to BTLE but now it’s also the other way around.

I’ve decided to do some testing.

I wore the Viiiiva (nope, I will not show it on my chest:)).


Pulled out the battery from my ANT+ foot pod.


So only the BTLE foot pod was working.

20141101_185928 20141101_185936

Immediately afterwards the BTLE foot pod was found:

20141101_185830 20141101_185953

I was moving it around in the air and the watch actually shows the pace:


I have configured the Viiiiva to retransmit the foot pod over bluetooth:


At the end I ran miCoach, pair the sensors and you can see that once I started the run the sensor were successfully found by the app (green icons in top right corner – both foot pod and heart rate monitor).


Which means the signal from BTLE foot pod can be simultaneously bridged to ANT+ and BTLE devices and we can use both foot pod and heart rate monitor!

The way how i suspect it to work is as follows:

– Viiiva search for BTLE foot pod

– Automatically connects to it

– Transform the signal into ANT+ and starts the transmission

– Retransmit the foot pod bluetooth signal so other app could connects with it (that’s what is done in the application when selecting the foot pod)

But that’s only my guess (but at this point seems legit for me;)).

After the configuration I’ve done a 10km test run. The configuration works without any problems. Below screenshots from Garmin Connect, Endomondo and miCoach – all with cadence data and heart rate data.

endomondo 4iiii garmin connect 4iii micoach 4iiii

I further check the compatibility of the BTLE to ANT+ bridge with other apps that supports foot pod on Android:

Application Screenshots
Garmin Fit Screenshot_2014-11-01-19-03-45
Sportstracklive PRO Screenshot_2014-11-01-19-04-43 Screenshot_2014-11-01-19-05-05

Both Garmin Fit and Sportstracklive PRO have found the footpod.

This firmware upgrade from 4iiii eliminates the need for many of us to have 2 foot pods. It also gave the real reason to have BTLE foot pod.

This probably also works for other devices like power meters but I have no opportunity to check this.

For engineers at 4iiii – thanks for the firmware upgrade and keep up the good work!

For marketing guys at 4iii – shame on you! You have released such cool feature and I could not find the info about this anywhere – your site, facebook profile. Why!?

If you have any questions or configurations you would like me to check – please ask in comments.

As always – thanks for reading.

[Update: video]


  • Hi Mario
    Regarding your update 3 have you tried taking the Viiiiva completely out of the equation to see if the footpod is transmitting a very week ANT+ signal?

    You would assume that even if the signal is weak your Garmin watch should still pick it up if close enough like in your video.

  • Hi Gary, yes I have tried this also without Viiiiva and it worked just fine – was able to complete the whole workout with it several times. But I cannot rely on this solution because it doesn’t work always – I would say once every 3,4 times I wake up the foot pod I can connect my Garmin watch with it.

    Have tried many times with different combinations of turning on the devices in different order, holding the foot pod very close to the watch, short circuit the foot pod (with battery upside down for a while) etc. but I could not find any regularity in this. So I would not say buy speed_cell since it will give you dual band connectivity. But the fact is – the ANT+ signal is there. It’s just not active or strong enough every time to be picked up by the watch.

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