FAQ

Where do I start?

Bicycle, then motor, then battery, then firmware. Most standard bicycles work with the TSDZ2B motor, but check to make sure before you buy. Varstrom TSDZ2B motors are available from online retailers, eBay, and AliExpress, and batteries come from a variety of online sources. You’ll need an ST-Link to flash the motor firmware, and if you plan to use an 860C display, you’ll need to build a UART cable to flash the display firmware.

What is the TSDZ2B?

The TSDZ2B is a Tongsheng-branded mid-drive, torque-sensing motor. It bolts onto the bottom bracket of many standard bicycles, converting them into pedal-assist electric bikes - that’s the hardware this firmware runs on.

Is a TSDZ2B bike street legal?

Yes, in the US. A bike with a TSDZ2B is a pedal-assisted bicycle: you pedal, and the motor adds to your effort in proportion to how hard you pedal. It’s not an electric motorcycle or moped.

Most states sort electric bicycles into three classes, all limited to a motor under 750W:

• Class 1: the motor only helps while you pedal, and stops helping at 20 mph.
• Class 2: it can also have a throttle that moves the bike without pedaling, and the motor stops at 20 mph.
• Class 3: the motor only helps while you pedal, up to 28 mph, and the bike has a speedometer.

The TSDZ2B is rated at 500W or less, well under the 750W limit. It’s a small, light, torque-sensing motor built for pedal assist, and ridden without a throttle it’s a Class 1 pedal-assisted bicycle. If you add a throttle, the bike could be considered Class 2, though that’s debatable given how little the TSDZ2B can do on throttle alone.

Outside the US, set the firmware up to match your local rules. In the EU and UK, that generally means the 250W TSDZ2B, assist that stops at 25 km/h, and a throttle that works only up to 6 km/h, if at all.

Rules still vary by country, state, and city, so always check your local laws.

Where do I get support?

• GitHub Issues
• The Endless Sphere forums
• osf.bike forums (planned)

Is my controller/display supported?

Varstrom-branded TSDZ2B motors are supported, at 36V/48V and 250W/500W. On the display side: the DZ40 is supported if you want something minimalist, the 860C is supported if you want more advanced features - graphs, odometers, timers, and light sensors - and gets the full custom OSF Modern dashboard theme, and the SW102 is supported in hardware but firmware/flashing for it is still in development.

Is the TSDZ8, TSDZ16, or Bafang BB-series supported?

Not yet - the firmware currently runs on the TSDZ2B only. The architecture is built for more, though: the project’s goal is a universal wire protocol so any display can talk to any motor controller, and once both ends run osf.bike they just work. The TSDZ8, TSDZ16, and Bafang BB-series motors aren’t supported today - if you want to see that change, check out how to get involved.

How do I get involved?

Use the firmware, share what you learn on the forums, and fork the project to help with its development.