Reading HR from an ANT+/BLE device

As the HR sensor is not reliable for sports, it can be interesting bangle.js can read from a remote BLE or ANT+ HR sensor.

Due BLE limitations a connection to HR sensor will not allow gadget bridge simultaneously.

However, ANT+ allows multiple connection,and it seems that ANT+ is supported by nRF52 series and its softdevices.
As Garmin sensors have been using ANT+ for many years, it is no difficult to find them.

Is it feasible to include ANT support? easier from BLE?

Evaluation Use:
• Not to be used for any commercial or revenue-generating purpose.
• Click above for Evaluation use on any of the stack downloads for the SoftDevices that you need.

The SoftDevices are available as ANT-only (200 series) and concurrent ANT and Bluetooth (300 series), providing flexibility to serve specific product needs

https://www.thisisant.com/developer/components/nrf52832/#tab_protocol_stacks_tab

Due BLE limitations a connection to HR sensor will not allow gadget bridge simultaneously.

There should be no such limitation, you can connect from bangle to some other peripheral device while gb is connected to bangle. Current configuration allows one central and one concurrent peripheral connection.

The combined ANT+BLE softdevice will be definitely larger and additional support would need some extra espruino code so quite likely it won't fit as even now the current firmware size is very tight fit. It would be much easier to add multiple bluetooth connections.

Also ANT needs additional license https://www.thisisant.com/developer/components/view-all-components/nrf52-ant-stack-licensing-faq

I am not an expert in licenses but I am not sure that bangle.js can't use the evaluation licenee

"A license key and a commercial use agreement are required for use of the S212 and/or S332 in revenue-generating applications."

"Selling products with an evaluation stack will obligate you to royalties"

IMO after Bangle.js has been sold/bought there is not more revenue generated, so a later flashing should be allowed and also the application software that would use ANT+ are all non commercial.

On the other hand, the previous discussion is not much important if SD size is a problem or there is not a demand from users.