SW102 Firmware

Custom firmware - Bafang SW102 display

Your Bafang SW102 display, completely reprogrammed.

Open-source firmware that replaces the stock SW102 firmware entirely - a redesigned cockpit, a full settings menu, and Bluetooth OTA updates, built from scratch for genuine Bafang mid-drive controllers (BBS01/BBS02/BBSHD/M400/M420/M620).

View on GitHub → v0.1.5

nRF51822 · Free & open source · Bluetooth OTA updates

Real hardware

Running on an actual SW102 display.

Boot screen

Cockpit

Cockpit (large speed)

Data screen

SW102 cockpit with the arrow-style assist level indicator

Assist level, Type B

Rotated 180 degrees

Assist level programming

Cockpit

Everything a factory display shows - redesigned.

Battery voltage and percentage (Standard, or Precise - computed locally from measured voltage)
Speed, in large digits - three layouts, cycled with a short press of M: standard, whole-number speed even larger, and a data screen
Motor power, in watts
Assist level - two selectable layouts, with a bar-graph or an arrow-based indicator, plus light/Bluetooth/brake status icons
Trip distance with one decimal, counted exactly at any speed, plus odometer and an estimated range based on your own riding history
Average and current energy consumption (Wh/km or Wh/mile)
Data screen: trip distance, average and top speed, total and moving time, maximum current and power, consumption, energy used - remembered after power-off and cleared only by Trip reset
On the data screen, an assist level change shows the new level big in the middle, with "PAS" underneath, for 3 seconds
STREET/RACE: a second, independent assist-level table kept on the display. Hold UP + DOWN for 3 seconds to switch; the active profile (S or R) shows in the top bar.

Settings menu

A full menu, built from scratch.

Unit switch (km/h / mph), wheel size, speed limit, auto power off
Brightness - manual or automatic, with a live preview while you adjust the level
Current and voltage calibration for shunt-modded controllers or an off-reading voltage divider
Odometer correction, trip reset, and full factory reset
Battery percentage mode (Standard or Precise) with configurable min/max pack voltage
Cockpit layout options - assist-level layout, indicator style, separators, and turning the whole display upside down (remembered after power-off)
Assist Level Programming - read and edit the controller's own per-level current and speed limits, then save them back, plus the STREET/RACE option (USE RACE)
Screen test and firmware/hardware info

Under the hood

Built for genuine Bafang controllers.

UART

Native Bafang protocol

Speaks the standard Bafang display UART protocol directly - no intermediate box, no adapter.

OTA

Bluetooth updates

Update the firmware over Bluetooth after the first flash - no need to open the display again. Watch how it works.

Accurate battery %

Battery voltage measured in 0.1 V steps. Optional Precise mode computes the battery percentage locally from that voltage, for controllers whose own reporting runs inaccurate.

Range estimator

A real energy-use model blends your riding history with your current style into a live range estimate - not a static number.

GPL

Open source

Built on top of the community anszom/SW102_LCD fork, itself GPL-3.0 licensed.

SIM

Terminal emulator

A Rust-based emulator compiles and runs the real firmware C code on a PC, for testing layout and logic without hardware.

MCU

nRF51822

Runs on the display's existing Nordic nRF51822 BLE SoC - no hardware modification needed.

Compatible controllers

BBS01/BBS01B, BBS02/BBS02B, BBSHD, M400, M420, M620/G510 Ultra - the standard Bafang display protocol family.

✓

Nothing leaves the display.

This is firmware, not an app - it has no internet connection of any kind. It talks to the motor controller over a wired UART cable, and to a phone over Bluetooth only for firmware updates (DFU) - nothing is ever sent anywhere online.

✓No internet connectivity, ever

✓No account, no analytics, no tracking

✓Bluetooth used only for firmware updates

✓Riding data stays on the display itself