Keiser M3i

Zach CardozaTulare, CA

I co-developed the broadcast Bluetooth protocol that powers the Keiser M3i indoor cycling bike, working alongside Keiser's contracting electrical engineer. The protocol uses the three Bluetooth broadcast channels to carry real-time telemetry from as many as 254 bikes in a single class. I also built the iOS and Android companion apps, which reached around a quarter million downloads without any marketing spend behind them.

Role
Software Engineer
Employer
Keiser Corporation
Dates
2013 - 2018
Scale
  • 200,000+ units sold
  • Class systems support up to 254 simultaneous bikes
  • Standard bike at LA Fitness and Orangetheory Fitness
  • Bike of choice for most independent spin studios
  • Best-selling indoor cycling bike in the world at peak
Outcomes
  • One of the earliest Bluetooth 4.0 (BLE) consumer devices on the market
  • Around 250,000 organic downloads of the consumer companion apps
Tech
  • Bluetooth Low Energy
  • Custom broadcast protocol
  • Nordic NRF52 firmware
  • iOS, Android

There was no off-the-shelf protocol that fit what the M3i needed: real-time telemetry from a room full of bikes to a single receiver. The contracting electrical engineer and I co-developed a custom broadcast-only Bluetooth protocol that used the three BT broadcast channels, capable of supporting up to 254 simultaneous bikes per class (256 minus reserved IDs). Built on custom Nordic NRF52 firmware initially. Later commoditized to off-the-shelf hardware sourced from China after iPhone iBeacon broadcasts started causing collisions in the original receivers.

The in-class projection system reads telemetry from every bike in the room and renders dials, leaderboards, and per-rider metrics on a projector or display. The consumer companion apps were a separate workstream: simple bike pairing, workout history, and stats sharing. They reached around 250,000 organic downloads without marketing spend, which surprised everyone.

Industry-partnership trainer apps followed: tools that let professional sports trainers walk a room and see live per-bike telemetry on their phones. The partnerships I worked through during this period spanned most of the Premier League, most of the Bundesliga, the Spanish soccer leagues, and the majority of US professional sports teams (with a few notable exceptions). The M3i itself eventually became the standard bike at LA Fitness and Orangetheory Fitness, and the bike of choice for most independent spin studios.