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UPDATE: Wireless timing with a Raspberry Pi

Hello all,

I posted on this site some time back about a concept using a Raspberry Pi to send ToD data from the start to the results PC for FIS legal wireless timing. I've continued working on it over the season in my spare time, with some invaluable help with testing and debugging from Wally at Apex Mountain. I thought I'd post our progress.

The concept works with some custom software, which I've named Ullr after the patron god of skiing and because it wasn't already taken.


The signal flow is similar to before: the System A timer at the start is plugged into a Raspberry Pi, that forwards messages to the "cloud", in this case an MQTT broker. The MQTT broker then ensures delivery to the PC in the finish.

The obvious downside to this approach is that it requires an internet connection. Without an internet connection it won't work. The upsides are that it's sending ToD data rather than pulses, has no distance or line-of-sight limitations, and it's cheap! A Raspberry Pi costs about $30 with a case, and the software is free and open source.

The software also works as a hub of sorts, to allow the connection of multiple timers to software like Ski Club that only support one. I was able to connect a CP540 wireless from the start, a CP540 hardwired from the finish, and a Racetime2 running some wireless splits, all into Ski Club. There is also the possibility, so far untested, of using the software to run a display board in a remote location.

The project page with much more detail and explanation is here: I'd love it if someone else found the project useful. I'd also love any feedback, criticism, or feature ideas!

Thanks for looking,



Images (1)
  • Ullr: Ski racing signal flow.

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First off, thank you for generously sharing all your work with the timing community (Wally too).

In under 4 hours from UPS delivery to my first screenshots, I had a Timy and a CP520 sending/receiving data on both my local and remote computers.

Another 30 or 40 minutes today and I have data transferred to my timing software.

Super useful and I can think of plenty of potential for this to be deployed. On to laying out my Pelican case!


This is a simple, inexpensive cloud based system. We ran six race days with the Pi and Zach's software as the B system, feeding data to Split Second's Ski Club program. As mentioned in the Ullr documentation, second timer capability is not required for the system to work, and in fact we were able to race using three timers (start, intermediate, finish) in the Ski Club software once correct configurations were set.

In more than 800 starts, four pulses did not transmit to timing, due to two incidents of internet connection loss (these starts' TOD data were captured by the timer at the start).

Pictures below show the kit sent to the start each day. The repurposed retro timer case proved to be adequately weatherproof for ski racing conditions. Operators were instructed to make occasional checks for printer tape obstruction through the day; no problems were encountered.

  • Alge Timy
  • USB power bank, 10,000 mAh capacity
  • "Mifi" cellular internet hotspot
  • Raspberry Pi Zero W single board computer (out of sight below foam)
  • USB-serial converter (out of sight below foam)



I am a complete Raspberry Pi/Linux rookie, but was able to install and run the software - with some help from Zach. I have about USD 100 invested so far, as I had some items already at hand.

  • Pi Zero W starter kit $50
  • USB power bank $15
  • wifi hotspot, used $35

Much gratitude to Zach for his hard work on this project. It gives us as timers a lot of possibilities: to race or train where no hard wiring exists, or to quickly add intermediate timing locations. Point to point races can be run where wired connections do not exist; use GPS sync and the timers would never need to be brought to the same physical location.


Images (4)
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