One of the most important features of modern, computerized, radios is that you can make them talk to you. After all, with setup telemetry link from UAV, radio should "know" things. Things like battery voltage for example. Why not make FrSky Taranis (or Horus or Taranis X Q7) talk to you and report LiPo voltage in a smart way?

Before we proceed, you have to setup SmartPort telemetry or "legacy" FrSky telemetry. This post does not covers this topic. You might want to take a look here and here.

Let's go

In OpenTX menu navigate to last page called Telemetry and check if VFAS is reporting proper value.

Go back (long press of PAGE button) 2 pages to LOGICAL SWITCHES and setup 2 switches:

  • L1 that activates when battery voltage is below threshold. I'm using 4S and decied to use 13.8V as my threshold value. In my case, I'm using Switch B for arming, so I also included it in this condition. I want Taranis to send me warnings and report voltage only when I'm armed.
  • L2 of a type Sticky that will activate for 5 seconds when switch L1 goes off. This Sticky logical switch protects us from the case when voltage crosses the threshold for a few times in short period of time.

Go forward to SPECIAL FUNCTIONS page and setup two functions:

  • SF1 that plays VFAS voltage every 20 seconds when quad is armed (SB not in top position)
  • SF2 that plays lowbat warning when L2 logical switch is on: VFAS goes below threshold but not more often than every 5 seconds