Frsky Taranis RSSI based Lap Timer

If you are looking for a free RSSI based lap timer for your Taranis or opentx radio then this might be what you are looking for. There are some very impressive lap timing systems already out there, but found that for my purposes they were either were too complex for my needs, or didn’t have all the features that I wanted. Specifically I wanted the timer to

  • be simple to use
  • trigger lap times using RSSI signal
  • verbally tell you your lap times
  • save a log of the times if I wanted to

There has already been a lot of excellent systems built out there, and decided to modify an existing project that *almost* did everything I wanted which can be found at Jeremy Cowgars very excellent opentx laptimer.

Installation Instructions

  • Download laptimer from here
  • Copy the contents of the zip file directly to the base folder of the SD card in your Taranis
  • In your model setup, go to the telemetry page and setup one of the screens to use a “Script” called “Laptime” you just copied to the SD card. If you dont have a “Script” option for the telemetry screens its possible you do not have firmware loaded that has LUA script like this one. If you would like instructions on how to install this firmware have a look at this page for instructions.

taranis-laptimer-01-telemetry-setup-screen

  • Setup a logical switch to trigger the lap timer using RSSI as shown below. The 87db defined here is the threshold used to trigger a lap, and the duration of 6 seconds is important to make sure it only triggers once per lap.

taranis-laptimer-02-logical-switches-rssi-only

  • Exit out of the model setup, then just press and hold the “Page” button and the lap timer should start up and show the initial setup screen, mode 2 users should be able to just press exit to get started if you setup the logical switch as above, otherwise you might need to change the lap switch. You can check Jeremys page for details on what these options do.

taranis-laptimer-03-config-screen

How to use it

  • This is the main screen you will be greeted with each time you start the lap timer, just select the number of laps  and hit enter.

taranis-laptimer-03-main-screen

  • This screen will appear and wait for you to bring up the throttle, that will trigger the lap timer to start

taranis-laptimer-04-race-start

  • Once its running you will see each lap time appear on the right hand side

taranis-laptimer-05-timer-screen

  • Once you’ve finished all the laps it will show you the summary of results, at which time you can choose to save the results to the SD card or discard them

taranis-laptimer-06-save-results

More advanced stuff and troubleshooting

Triggering with switches

I prefer to have the lap timer able to be triggered by switch as well as RSSI in case I am in a situation I can’t use the RSSI triggering (lap loops back close to the finish line before end of a lap), this is the setup that I use. Don’t forget to change the config in the timer to point to the new logical switch.

taranis-laptimer-02-logical-switches-dual-trigger

Not reliably triggering

I found that for best results I needed to be standing not more than a 4 or 5 meters from the finish line, with a higher RSSI trigger dB. You can try other combinations, but basically if you want it to be more sensitive because you are missing laps decrease the dB number, if its triggering too often increase it.

If your race course loops around to a spot near the start, its possible to get a false triggering of the lap timer as you’d expect.

To give you an idea, I have a quad with the antenna taped to the arms which triggers at around 75db, and another that triggers at 87db as its antenna and standing up to provide better reception.

Can’t start it up

This has been tested with opentx 2.1.8 with LUA script enabled which can be found here easiest way to flash this would be to copy the firmware into the firmware folder on your SD card, then start up your Taranis in bootloader mode to flash the firmware onto it.

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