Introduction
ServoSim is a real time virtual servo monitor which I designed to help explore the programming of complex R/C transmitters, in particular the Multiplex mc4000.
The heart of the system is a custom interface which reads servo commands from the transmitter's DSC socket, and converts it to a serial stream.
The channel data is read by a PC and displayed on the monitor.
Host Program Features
- Runs under Windows 3.x/NT/2000/XP
- Displays all 7, 9 or 12 channels
- Dual mode display (servo or bargraph).
- Auto-adjusts for MPX and non-MPX neutrals
- Rf signal is disabled during operation
Supported Tx's
The system has been tried with
- MPX4000
- MPX3030
- Futaba FF7
- Spektrum DX-7
Technical Overview
PIC Interface
The interface uses a PIC 16F628 microcontroller and MAX233 serial driver, external Xtal oscillator and a few other components.
Firmware
The PIC monitors the DSC signal. In most systems, this is a series of short (~300 microsecond) negative going spikes. The pulse widths are calculated by measuring the interval between successive spikes.
The measured pulse widths are encoded into 3-character hex strings, and transmitted to the PC via the UART and serial line driver.
PC Software
A program writen in VB5 reads the hex character stream from the serial port, calculates the pulse widths, and displays the results.
Hardware Photos
Version 1 (left): The picture above shows the EPROM programmer and Lab X2 dev board.
Version 2 (left). This is on a board 70mm x 60mm.
Version 3 is smaller still and uses just 9 components (no picture available)
Screenshots
All shots show "Bargraph" display mode
Switch on the Tx. Note that the servo's are not quite centred, so...
Set a new baseline. No movement until...
The Aileron stick is moved. The wing servos (along the top line) respond.
So do the V-tail servos, due to combi mix.
Menus
This is the "Mark" menu for setting a new baseline.
The Options menu selects MPX or Futaba/JR/Hitec neutrals.
You can select a number of viewing options.
Availability
There are currently no plans to make this system available.