SWYFT Servo Programmer V2

A modern Windows desktop utility from SWYFT Robotics for reading and writing RC servo parameters over a single-wire half-duplex UART link (USB-to-UART adapter).

This is a clean-room rewrite of an older internal tool. The legacy app was a .NET Framework 4.0 WinForms program; its source was lost, so the wire protocol was recovered by decompiling the shipped binary and re-implemented here on .NET 8 / WPF with a refreshed UI and several usability improvements.

Features

• Automatic adapter detection on startup — finds the USB-to-UART adapter by name (no button to press)
• Read Servo to pull current parameters and Flash Servo to write edited parameters back
• Every parameter editable via a validated numeric field with range checking
• Total Range (0–320°) control plus a Continuous Rotation toggle (handles the Left/Right math for you)
• Direction (CW/CCW), stall protection and Ramp Mode as toggle switches
• Set defaults button to restore SWYFT's recommended baseline values
• Built-in guide (Getting Started + setting explanations + wiring diagram)
• Bundled CP210x USB driver — a USB driver button opens the driver folder for manual install
• Timestamped activity log and live connection status

Requirements

• Windows 10/11
• .NET 8 SDK (to build) or the .NET 8 Desktop Runtime (to run)
• A USB-to-UART adapter wired for single-wire half-duplex to the servo signal line

Build & run

cd src
dotnet build
dotnet run

To produce a self-contained single executable:

cd src
dotnet publish -c Release -r win-x64 --self-contained true `
  -p:PublishSingleFile=true -p:IncludeNativeLibrariesForSelfExtract=true

Wiring

The servo communicates on a single signal wire (half-duplex). Tie the adapter's TX and RX together to that wire (typically through the adapter's single-wire mode or a resistor/diode), share ground, and power the servo from an appropriate supply. Because TX and RX are shared, the bytes the PC sends are echoed back; the app discards that echo automatically.

Serial / protocol summary

• 115200 baud, 8 data bits, no parity, 2 stop bits (8-N-2)
• Every message is a fixed 20-byte frame:

Byte	Meaning
0	Header 0x55
1..17	Payload (see below)
18	Checksum = (sum of bytes 1..17) & 0xFF
19	Footer 0xAA

Payload (UI name → firmware field):

Byte(s)	UI name	Firmware field	Encoding
1	P coefficient	Torque proportion	byte
2	I coefficient	Integral proportion	byte
3	Flags	—	bit0 direction, bit1 write-request, bit2 write-ack, bit3 read-valid, bit4 stall, bit5 ramp
4	Left range	Angle proportion (max side)	byte
5	Dead Zone	Sensitivity	byte
6	Integral speed	Integral speed (×3 ms)	byte
7,8	D coefficient	Brake proportion	uint16 LE
9,10	Min Signal (µs)	Min pulse width	uint16 LE
11,12	Max Signal (µs)	Max pulse width	uint16 LE
13,14	Max Power	Max duty cycle	uint16 LE
15	Right range	Angle proportion (min side)	byte
16,17	Middle Signal (µs)	Center / median	uint16 LE

Travel range & continuous rotation

Left and Right range are not edited directly. The UI exposes a single Total Range (0–320°) control; it is split evenly and written to both Left and Right range using the linear calibration degrees = (50·V − 420) / 19 (so 270° → 111 per side, 320° → 130 per side). Enabling Continuous rotation forces both Left and Right range to 255 (full-speed continuous rotation).

• Read: host sends a frame with header/footer and an all-zero payload; the servo replies with a full frame (valid when the checksum matches and the read-valid bit 0x08 is set).
• Write: host sends the populated frame; the servo echoes a frame with the write-ack bit 0x04 set on success.

Note: the slider ranges for pulse widths (500–2500 µs) reflect typical RC servo values. If your hardware uses a different range, adjust the limits in ViewModels/MainViewModel.cs (BuildParameters).

Project layout

src/
  Models/        ServoParameters, ParameterKey
  Protocol/      ServoProtocol  (frame build/parse — pure, unit-testable)
  Services/      ServoConnection (serial I/O, WMI port detection), SerialSettings, DriverInstaller
  ViewModels/    MainViewModel, ParameterViewModel, LogEntry
  Infrastructure/ ObservableObject, RelayCommand, AsyncRelayCommand
  Themes/        Brand.xaml (SWYFT colors #01A1FF / white)
  Assets/        Logo, wordmark, app icon, wiring diagram
  Drivers/       Bundled CP210x USB-UART driver
  MainWindow.xaml / GuideWindow.xaml / App.xaml

Download

Prebuilt Windows downloads are published on the Releases page. The release is a self-contained build — no .NET runtime install required, just unzip and run SwyftServoProgrammerV2.exe.

License

Released under the MIT License. © 2026 SWYFT Robotics.